1 | .\" $NetBSD: sh.1,v 1.80 2005/05/24 00:03:52 wiz Exp $
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2 | .\" Copyright (c) 1991, 1993
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3 | .\" The Regents of the University of California. All rights reserved.
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4 | .\"
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5 | .\" This code is derived from software contributed to Berkeley by
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6 | .\" Kenneth Almquist.
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7 | .\"
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8 | .\" Redistribution and use in source and binary forms, with or without
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9 | .\" modification, are permitted provided that the following conditions
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10 | .\" are met:
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11 | .\" 1. Redistributions of source code must retain the above copyright
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12 | .\" notice, this list of conditions and the following disclaimer.
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13 | .\" 2. Redistributions in binary form must reproduce the above copyright
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14 | .\" notice, this list of conditions and the following disclaimer in the
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15 | .\" documentation and/or other materials provided with the distribution.
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16 | .\" 3. Neither the name of the University nor the names of its contributors
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17 | .\" may be used to endorse or promote products derived from this software
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18 | .\" without specific prior written permission.
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19 | .\"
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20 | .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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21 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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22 | .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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23 | .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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24 | .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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25 | .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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26 | .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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27 | .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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28 | .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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29 | .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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30 | .\" SUCH DAMAGE.
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31 | .\"
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32 | .\" @(#)sh.1 8.6 (Berkeley) 5/4/95
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33 | .\"
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34 | .Dd May 7, 2005
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35 | .Os
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36 | .Dt SH 1
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37 | .Sh NAME
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38 | .Nm sh
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39 | .Nd command interpreter (shell)
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40 | .Sh SYNOPSIS
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41 | .Nm
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42 | .Bk -words
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43 | .Op Fl aCefnuvxIimqVEb
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44 | .Op Cm +aCefnuvxIimqVEb
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45 | .Ek
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46 | .Bk -words
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47 | .Op Fl o Ar option_name
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48 | .Op Cm +o Ar option_name
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49 | .Ek
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50 | .Bk -words
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51 | .Op Ar command_file Oo Ar argument ... Oc
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52 | .Ek
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53 | .Nm
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54 | .Fl c
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55 | .Bk -words
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56 | .Op Fl aCefnuvxIimqVEb
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57 | .Op Cm +aCefnuvxIimqVEb
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58 | .Ek
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59 | .Bk -words
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60 | .Op Fl o Ar option_name
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61 | .Op Cm +o Ar option_name
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62 | .Ek
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63 | .Bk -words
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64 | .Ar command_string
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65 | .Op Ar command_name Oo Ar argument ... Oc
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66 | .Ek
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67 | .Nm
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68 | .Fl s
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69 | .Bk -words
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70 | .Op Fl aCefnuvxIimqVEb
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71 | .Op Cm +aCefnuvxIimqVEb
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72 | .Ek
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73 | .Bk -words
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74 | .Op Fl o Ar option_name
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75 | .Op Cm +o Ar option_name
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76 | .Ek
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77 | .Bk -words
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78 | .Op Ar argument ...
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79 | .Ek
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80 | .Sh DESCRIPTION
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81 | .Nm
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82 | is the standard command interpreter for the system.
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83 | The current version of
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84 | .Nm
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85 | is in the process of being changed to conform with the
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86 | .Tn POSIX
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87 | 1003.2 and 1003.2a specifications for the shell.
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88 | This version has many
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89 | features which make it appear similar in some respects to the Korn shell,
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90 | but it is not a Korn shell clone (see
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91 | .Xr ksh 1 ) .
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92 | Only features designated by
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93 | .Tn POSIX ,
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94 | plus a few Berkeley extensions, are being incorporated into this shell.
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95 | .\" We expect
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96 | .\" .Tn POSIX
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97 | .\" conformance by the time 4.4 BSD is released.
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98 | This man page is not intended
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99 | to be a tutorial or a complete specification of the shell.
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100 | .Ss Overview
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101 | The shell is a command that reads lines from either a file or the
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102 | terminal, interprets them, and generally executes other commands.
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103 | It is the program that is running when a user logs into the system
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104 | (although a user can select a different shell with the
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105 | .Xr chsh 1
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106 | command).
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107 | The shell implements a language that has flow control
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108 | constructs, a macro facility that provides a variety of features in
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109 | addition to data storage, along with built in history and line editing
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110 | capabilities.
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111 | It incorporates many features to aid interactive use and
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112 | has the advantage that the interpretative language is common to both
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113 | interactive and non-interactive use (shell scripts).
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114 | That is, commands
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115 | can be typed directly to the running shell or can be put into a file and
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116 | the file can be executed directly by the shell.
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117 | .Ss Invocation
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118 | If no args are present and if the standard input of the shell
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119 | is connected to a terminal (or if the
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120 | .Fl i
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121 | flag is set),
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122 | and the
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123 | .Fl c
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124 | option is not present, the shell is considered an interactive shell.
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125 | An interactive shell generally prompts before each command and handles
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126 | programming and command errors differently (as described below).
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127 | When first starting,
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128 | the shell inspects argument 0, and if it begins with a dash
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129 | .Sq - ,
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130 | the shell is also considered
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131 | a login shell.
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132 | This is normally done automatically by the system
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133 | when the user first logs in.
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134 | A login shell first reads commands
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135 | from the files
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136 | .Pa /etc/profile
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137 | and
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138 | .Pa .profile
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139 | if they exist.
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140 | If the environment variable
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141 | .Ev ENV
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142 | is set on entry to a shell, or is set in the
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143 | .Pa .profile
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144 | of a login shell, the shell next reads
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145 | commands from the file named in
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146 | .Ev ENV .
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147 | Therefore, a user should place commands that are to be executed only at
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148 | login time in the
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149 | .Pa .profile
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150 | file, and commands that are executed for every shell inside the
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151 | .Ev ENV
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152 | file.
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153 | To set the
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154 | .Ev ENV
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155 | variable to some file, place the following line in your
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156 | .Pa .profile
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157 | of your home directory
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158 | .Pp
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159 | .Dl ENV=$HOME/.shinit; export ENV
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160 | .Pp
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161 | substituting for
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162 | .Dq .shinit
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163 | any filename you wish.
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164 | Since the
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165 | .Ev ENV
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166 | file is read for every invocation of the shell, including shell scripts
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167 | and non-interactive shells, the following paradigm is useful for
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168 | restricting commands in the
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169 | .Ev ENV
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170 | file to interactive invocations.
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171 | Place commands within the
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172 | .Dq case
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173 | and
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174 | .Dq esac
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175 | below (these commands are described later):
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176 | .Pp
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177 | .Bl -item -compact -offset indent
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178 | .It
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179 | .Li case $- in *i*)
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180 | .Bl -item -compact -offset indent
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181 | .It
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182 | .Li # commands for interactive use only
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183 | .It
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184 | .Li ...
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185 | .El
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186 | .It
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187 | .Li esac
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188 | .El
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189 | .Pp
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190 | If command line arguments besides the options have been specified, then
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191 | the shell treats the first argument as the name of a file from which to
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192 | read commands (a shell script), and the remaining arguments are set as the
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193 | positional parameters of the shell ($1, $2, etc).
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194 | Otherwise, the shell
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195 | reads commands from its standard input.
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196 | .Ss Argument List Processing
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197 | All of the single letter options have a corresponding name that can be
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198 | used as an argument to the
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199 | .Fl o
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200 | option.
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201 | The set
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202 | .Fl o
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203 | name is provided next to the single letter option in
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204 | the description below.
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205 | Specifying a dash
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206 | .Dq -
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207 | turns the option on, while using a plus
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208 | .Dq +
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209 | disables the option.
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210 | The following options can be set from the command line or
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211 | with the
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212 | .Ic set
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213 | builtin (described later).
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214 | .Bl -tag -width aaaallexportfoo -offset indent
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215 | .It Fl a Em allexport
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216 | Export all variables assigned to.
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217 | .It Fl c
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218 | Read commands from the
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219 | .Ar command_string
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220 | operand instead of from the standard input.
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221 | Special parameter 0 will be set from the
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222 | .Ar command_name
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223 | operand and the positional parameters ($1, $2, etc.)
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224 | set from the remaining argument operands.
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225 | .It Fl C Em noclobber
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226 | Don't overwrite existing files with
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227 | .Dq \*[Gt] .
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228 | .It Fl e Em errexit
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229 | If not interactive, exit immediately if any untested command fails.
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230 | The exit status of a command is considered to be
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231 | explicitly tested if the command is used to control an
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232 | .Ic if ,
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233 | .Ic elif ,
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234 | .Ic while ,
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235 | or
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236 | .Ic until ;
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237 | or if the command is the left hand operand of an
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238 | .Dq \*[Am]\*[Am]
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239 | or
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240 | .Dq ||
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241 | operator.
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242 | .It Fl f Em noglob
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243 | Disable pathname expansion.
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244 | .It Fl n Em noexec
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245 | If not interactive, read commands but do not execute them.
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246 | This is useful for checking the syntax of shell scripts.
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247 | .It Fl u Em nounset
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248 | Write a message to standard error when attempting to expand a variable
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249 | that is not set, and if the shell is not interactive, exit immediately.
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250 | .It Fl v Em verbose
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251 | The shell writes its input to standard error as it is read.
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252 | Useful for debugging.
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253 | .It Fl x Em xtrace
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254 | Write each command to standard error (preceded by a
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255 | .Sq +\ )
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256 | before it is executed.
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257 | Useful for debugging.
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258 | .It Fl q Em quietprofile
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259 | If the
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260 | .Fl v
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261 | or
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262 | .Fl x
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263 | options have been set, do not apply them when reading
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264 | initialization files, these being
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265 | .Pa /etc/profile ,
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266 | .Pa .profile ,
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267 | and the file specified by the
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268 | .Ev ENV
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269 | environment variable.
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270 | .It Fl I Em ignoreeof
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271 | Ignore EOF's from input when interactive.
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272 | .It Fl i Em interactive
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273 | Force the shell to behave interactively.
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274 | .It Fl m Em monitor
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275 | Turn on job control (set automatically when interactive).
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276 | .It Fl s Em stdin
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277 | Read commands from standard input (set automatically if no file arguments
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278 | are present).
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279 | This option has no effect when set after the shell has
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280 | already started running (i.e. with
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281 | .Ic set ) .
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282 | .It Fl V Em vi
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283 | Enable the built-in
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284 | .Xr vi 1
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285 | command line editor (disables
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286 | .Fl E
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287 | if it has been set).
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288 | (See the
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289 | .Sx Command Line Editing
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290 | section below.)
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291 | .It Fl E Em emacs
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292 | Enable the built-in emacs style
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293 | command line editor (disables
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294 | .Fl V
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295 | if it has been set).
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296 | (See the
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297 | .Sx Command Line Editing
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298 | section below.)
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299 | .It Fl b Em notify
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300 | Enable asynchronous notification of background job completion.
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301 | (UNIMPLEMENTED for 4.4alpha)
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302 | .It "\ \ " Em cdprint
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303 | Make an interactive shell always print the new directory name when
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304 | changed by the
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305 | .Ic cd
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306 | command.
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307 | .It "\ \ " Em tabcomplete
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308 | Enables filename completion in the command line editor.
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309 | Typing a tab character will extend the current input word to match a
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310 | filename.
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311 | If more than one filename matches it is only extended to be the common prefix.
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312 | Typing a second tab character will list all the matching names.
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313 | .El
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314 | .Ss Lexical Structure
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315 | The shell reads input in terms of lines from a file and breaks it up into
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316 | words at whitespace (blanks and tabs), and at certain sequences of
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317 | characters that are special to the shell called
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318 | .Dq operators .
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319 | There are two types of operators: control operators and redirection
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320 | operators (their meaning is discussed later).
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321 | Following is a list of operators:
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322 | .Bl -ohang -offset indent
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323 | .It "Control operators:"
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324 | .Dl \*[Am] \*[Am]\*[Am] \&( \&) \&; ;; | || \*[Lt]newline\*[Gt]
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325 | .It "Redirection operators:"
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326 | .Dl \*[Lt] \*[Gt] \*[Gt]| \*[Lt]\*[Lt] \*[Gt]\*[Gt] \*[Lt]\*[Am] \*[Gt]\*[Am] \*[Lt]\*[Lt]- \*[Lt]\*[Gt]
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327 | .El
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328 | .Ss Quoting
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329 | Quoting is used to remove the special meaning of certain characters or
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330 | words to the shell, such as operators, whitespace, or keywords.
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331 | There are three types of quoting: matched single quotes,
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332 | matched double quotes, and backslash.
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333 | .Ss Backslash
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334 | A backslash preserves the literal meaning of the following
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335 | character, with the exception of
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336 | .Aq newline .
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337 | A backslash preceding a
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338 | .Aq newline
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339 | is treated as a line continuation.
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340 | .Ss Single Quotes
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341 | Enclosing characters in single quotes preserves the literal meaning of all
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342 | the characters (except single quotes, making it impossible to put
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343 | single-quotes in a single-quoted string).
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344 | .Ss Double Quotes
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345 | Enclosing characters within double quotes preserves the literal
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346 | meaning of all characters except dollarsign
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347 | .Pq $ ,
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348 | backquote
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349 | .Pq ` ,
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350 | and backslash
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351 | .Pq \e .
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352 | The backslash inside double quotes is historically weird, and serves to
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353 | quote only the following characters:
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354 | .Dl $ ` \*q \e \*[Lt]newline\*[Gt] .
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355 | Otherwise it remains literal.
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356 | .Ss Reserved Words
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357 | Reserved words are words that have special meaning to the
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358 | shell and are recognized at the beginning of a line and
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359 | after a control operator.
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360 | The following are reserved words:
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361 | .Bl -column while while while while while -offset indent
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362 | .It ! Ta elif Ta fi Ta while Ta case
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363 | .It else Ta for Ta then Ta { Ta }
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364 | .It do Ta done Ta until Ta if Ta esac
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365 | .El
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366 | .Pp
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367 | Their meaning is discussed later.
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368 | .Ss Aliases
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369 | An alias is a name and corresponding value set using the
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370 | .Ic alias
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371 | builtin command.
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372 | Whenever a reserved word may occur (see above),
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373 | and after checking for reserved words, the shell
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374 | checks the word to see if it matches an alias.
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375 | If it does, it replaces it in the input stream with its value.
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376 | For example, if there is an alias called
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377 | .Dq lf
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378 | with the value
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379 | .Dq "ls -F" ,
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380 | then the input:
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381 | .Pp
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382 | .Dl lf foobar Aq return
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383 | .Pp
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384 | would become
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385 | .Pp
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386 | .Dl ls -F foobar Aq return
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387 | .Pp
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388 | Aliases provide a convenient way for naive users to create shorthands for
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389 | commands without having to learn how to create functions with arguments.
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390 | They can also be used to create lexically obscure code.
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391 | This use is discouraged.
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392 | .Ss Commands
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393 | The shell interprets the words it reads according to a language, the
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394 | specification of which is outside the scope of this man page (refer to the
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395 | BNF in the
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396 | .Tn POSIX
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397 | 1003.2 document).
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398 | Essentially though, a line is read and if the first
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399 | word of the line (or after a control operator) is not a reserved word,
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400 | then the shell has recognized a simple command.
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401 | Otherwise, a complex
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402 | command or some other special construct may have been recognized.
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403 | .Ss Simple Commands
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404 | If a simple command has been recognized, the shell performs
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405 | the following actions:
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406 | .Bl -enum -offset indent
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407 | .It
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408 | Leading words of the form
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409 | .Dq name=value
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410 | are stripped off and assigned to the environment of the simple command.
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411 | Redirection operators and their arguments (as described below) are
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412 | stripped off and saved for processing.
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413 | .It
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414 | The remaining words are expanded as described in
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415 | the section called
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416 | .Dq Expansions ,
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417 | and the first remaining word is considered the command name and the
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418 | command is located.
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419 | The remaining words are considered the arguments of the command.
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420 | If no command name resulted, then the
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421 | .Dq name=value
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422 | variable assignments recognized in item 1 affect the current shell.
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423 | .It
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424 | Redirections are performed as described in the next section.
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425 | .El
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426 | .Ss Redirections
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427 | Redirections are used to change where a command reads its input or sends
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428 | its output.
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429 | In general, redirections open, close, or duplicate an
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430 | existing reference to a file.
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431 | The overall format used for redirection is:
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432 | .Pp
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433 | .Dl [n] Va redir-op Ar file
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434 | .Pp
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435 | where
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436 | .Va redir-op
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437 | is one of the redirection operators mentioned previously.
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438 | Following is a list of the possible redirections.
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439 | The
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440 | .Bq n
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441 | is an optional number, as in
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442 | .Sq 3
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443 | (not
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444 | .Sq Bq 3 ) ,
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445 | that refers to a file descriptor.
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446 | .Bl -tag -width aaabsfiles -offset indent
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447 | .It [n] Ns \*[Gt] file
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448 | Redirect standard output (or n) to file.
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449 | .It [n] Ns \*[Gt]| file
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450 | Same, but override the
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451 | .Fl C
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452 | option.
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453 | .It [n] Ns \*[Gt]\*[Gt] file
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454 | Append standard output (or n) to file.
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455 | .It [n] Ns \*[Lt] file
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456 | Redirect standard input (or n) from file.
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457 | .It [n1] Ns \*[Lt]\*[Am] Ns n2
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458 | Duplicate standard input (or n1) from file descriptor n2.
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459 | .It [n] Ns \*[Lt]\*[Am]-
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460 | Close standard input (or n).
|
---|
461 | .It [n1] Ns \*[Gt]\*[Am] Ns n2
|
---|
462 | Duplicate standard output (or n1) to n2.
|
---|
463 | .It [n] Ns \*[Gt]\*[Am]-
|
---|
464 | Close standard output (or n).
|
---|
465 | .It [n] Ns \*[Lt]\*[Gt] file
|
---|
466 | Open file for reading and writing on standard input (or n).
|
---|
467 | .El
|
---|
468 | .Pp
|
---|
469 | The following redirection is often called a
|
---|
470 | .Dq here-document .
|
---|
471 | .Bl -item -offset indent
|
---|
472 | .It
|
---|
473 | .Li [n]\*[Lt]\*[Lt] delimiter
|
---|
474 | .Dl here-doc-text ...
|
---|
475 | .Li delimiter
|
---|
476 | .El
|
---|
477 | .Pp
|
---|
478 | All the text on successive lines up to the delimiter is saved away and
|
---|
479 | made available to the command on standard input, or file descriptor n if
|
---|
480 | it is specified.
|
---|
481 | If the delimiter as specified on the initial line is
|
---|
482 | quoted, then the here-doc-text is treated literally, otherwise the text is
|
---|
483 | subjected to parameter expansion, command substitution, and arithmetic
|
---|
484 | expansion (as described in the section on
|
---|
485 | .Dq Expansions ) .
|
---|
486 | If the operator is
|
---|
487 | .Dq \*[Lt]\*[Lt]-
|
---|
488 | instead of
|
---|
489 | .Dq \*[Lt]\*[Lt] ,
|
---|
490 | then leading tabs in the here-doc-text are stripped.
|
---|
491 | .Ss Search and Execution
|
---|
492 | There are three types of commands: shell functions, builtin commands, and
|
---|
493 | normal programs -- and the command is searched for (by name) in that order.
|
---|
494 | They each are executed in a different way.
|
---|
495 | .Pp
|
---|
496 | When a shell function is executed, all of the shell positional parameters
|
---|
497 | (except $0, which remains unchanged) are set to the arguments of the shell
|
---|
498 | function.
|
---|
499 | The variables which are explicitly placed in the environment of
|
---|
500 | the command (by placing assignments to them before the function name) are
|
---|
501 | made local to the function and are set to the values given.
|
---|
502 | Then the command given in the function definition is executed.
|
---|
503 | The positional parameters are restored to their original values
|
---|
504 | when the command completes.
|
---|
505 | This all occurs within the current shell.
|
---|
506 | .Pp
|
---|
507 | Shell builtins are executed internally to the shell, without spawning a
|
---|
508 | new process.
|
---|
509 | .Pp
|
---|
510 | Otherwise, if the command name doesn't match a function or builtin, the
|
---|
511 | command is searched for as a normal program in the file system (as
|
---|
512 | described in the next section).
|
---|
513 | When a normal program is executed, the shell runs the program,
|
---|
514 | passing the arguments and the environment to the program.
|
---|
515 | If the program is not a normal executable file (i.e., if it does
|
---|
516 | not begin with the "magic number" whose
|
---|
517 | .Tn ASCII
|
---|
518 | representation is "#!", so
|
---|
519 | .Xr execve 2
|
---|
520 | returns
|
---|
521 | .Er ENOEXEC
|
---|
522 | then) the shell will interpret the program in a subshell.
|
---|
523 | The child shell will reinitialize itself in this case,
|
---|
524 | so that the effect will be as if a
|
---|
525 | new shell had been invoked to handle the ad-hoc shell script, except that
|
---|
526 | the location of hashed commands located in the parent shell will be
|
---|
527 | remembered by the child.
|
---|
528 | .Pp
|
---|
529 | Note that previous versions of this document and the source code itself
|
---|
530 | misleadingly and sporadically refer to a shell script without a magic
|
---|
531 | number as a "shell procedure".
|
---|
532 | .Ss Path Search
|
---|
533 | When locating a command, the shell first looks to see if it has a shell
|
---|
534 | function by that name.
|
---|
535 | Then it looks for a builtin command by that name.
|
---|
536 | If a builtin command is not found, one of two things happen:
|
---|
537 | .Bl -enum
|
---|
538 | .It
|
---|
539 | Command names containing a slash are simply executed without performing
|
---|
540 | any searches.
|
---|
541 | .It
|
---|
542 | The shell searches each entry in
|
---|
543 | .Ev PATH
|
---|
544 | in turn for the command.
|
---|
545 | The value of the
|
---|
546 | .Ev PATH
|
---|
547 | variable should be a series of entries separated by colons.
|
---|
548 | Each entry consists of a directory name.
|
---|
549 | The current directory may be indicated
|
---|
550 | implicitly by an empty directory name, or explicitly by a single period.
|
---|
551 | .El
|
---|
552 | .Ss Command Exit Status
|
---|
553 | Each command has an exit status that can influence the behavior
|
---|
554 | of other shell commands.
|
---|
555 | The paradigm is that a command exits
|
---|
556 | with zero for normal or success, and non-zero for failure,
|
---|
557 | error, or a false indication.
|
---|
558 | The man page for each command
|
---|
559 | should indicate the various exit codes and what they mean.
|
---|
560 | Additionally, the builtin commands return exit codes, as does
|
---|
561 | an executed shell function.
|
---|
562 | .Pp
|
---|
563 | If a command consists entirely of variable assignments then the
|
---|
564 | exit status of the command is that of the last command substitution
|
---|
565 | if any, otherwise 0.
|
---|
566 | .Ss Complex Commands
|
---|
567 | Complex commands are combinations of simple commands with control
|
---|
568 | operators or reserved words, together creating a larger complex command.
|
---|
569 | More generally, a command is one of the following:
|
---|
570 | .Bl -bullet
|
---|
571 | .It
|
---|
572 | simple command
|
---|
573 | .It
|
---|
574 | pipeline
|
---|
575 | .It
|
---|
576 | list or compound-list
|
---|
577 | .It
|
---|
578 | compound command
|
---|
579 | .It
|
---|
580 | function definition
|
---|
581 | .El
|
---|
582 | .Pp
|
---|
583 | Unless otherwise stated, the exit status of a command is that of the last
|
---|
584 | simple command executed by the command.
|
---|
585 | .Ss Pipelines
|
---|
586 | A pipeline is a sequence of one or more commands separated
|
---|
587 | by the control operator |.
|
---|
588 | The standard output of all but
|
---|
589 | the last command is connected to the standard input
|
---|
590 | of the next command.
|
---|
591 | The standard output of the last
|
---|
592 | command is inherited from the shell, as usual.
|
---|
593 | .Pp
|
---|
594 | The format for a pipeline is:
|
---|
595 | .Pp
|
---|
596 | .Dl [!] command1 [ | command2 ...]
|
---|
597 | .Pp
|
---|
598 | The standard output of command1 is connected to the standard input of
|
---|
599 | command2.
|
---|
600 | The standard input, standard output, or both of a command is
|
---|
601 | considered to be assigned by the pipeline before any redirection specified
|
---|
602 | by redirection operators that are part of the command.
|
---|
603 | .Pp
|
---|
604 | If the pipeline is not in the background (discussed later), the shell
|
---|
605 | waits for all commands to complete.
|
---|
606 | .Pp
|
---|
607 | If the reserved word ! does not precede the pipeline, the exit status is
|
---|
608 | the exit status of the last command specified in the pipeline.
|
---|
609 | Otherwise, the exit status is the logical NOT of the exit status of the
|
---|
610 | last command.
|
---|
611 | That is, if the last command returns zero, the exit status
|
---|
612 | is 1; if the last command returns greater than zero, the exit status is
|
---|
613 | zero.
|
---|
614 | .Pp
|
---|
615 | Because pipeline assignment of standard input or standard output or both
|
---|
616 | takes place before redirection, it can be modified by redirection.
|
---|
617 | For example:
|
---|
618 | .Pp
|
---|
619 | .Dl $ command1 2\*[Gt]\*[Am]1 | command2
|
---|
620 | .Pp
|
---|
621 | sends both the standard output and standard error of command1
|
---|
622 | to the standard input of command2.
|
---|
623 | .Pp
|
---|
624 | A ; or
|
---|
625 | .Aq newline
|
---|
626 | terminator causes the preceding AND-OR-list (described
|
---|
627 | next) to be executed sequentially; a \*[Am] causes asynchronous execution of
|
---|
628 | the preceding AND-OR-list.
|
---|
629 | .Pp
|
---|
630 | Note that unlike some other shells, each process in the pipeline is a
|
---|
631 | child of the invoking shell (unless it is a shell builtin, in which case
|
---|
632 | it executes in the current shell -- but any effect it has on the
|
---|
633 | environment is wiped).
|
---|
634 | .Ss Background Commands -- \*[Am]
|
---|
635 | If a command is terminated by the control operator ampersand (\*[Am]), the
|
---|
636 | shell executes the command asynchronously -- that is, the shell does not
|
---|
637 | wait for the command to finish before executing the next command.
|
---|
638 | .Pp
|
---|
639 | The format for running a command in background is:
|
---|
640 | .Pp
|
---|
641 | .Dl command1 \*[Am] [command2 \*[Am] ...]
|
---|
642 | .Pp
|
---|
643 | If the shell is not interactive, the standard input of an asynchronous
|
---|
644 | command is set to
|
---|
645 | .Pa /dev/null .
|
---|
646 | .Ss Lists -- Generally Speaking
|
---|
647 | A list is a sequence of zero or more commands separated by newlines,
|
---|
648 | semicolons, or ampersands, and optionally terminated by one of these three
|
---|
649 | characters.
|
---|
650 | The commands in a list are executed in the order they are written.
|
---|
651 | If command is followed by an ampersand, the shell starts the
|
---|
652 | command and immediately proceed onto the next command; otherwise it waits
|
---|
653 | for the command to terminate before proceeding to the next one.
|
---|
654 | .Ss Short-Circuit List Operators
|
---|
655 | .Dq \*[Am]\*[Am]
|
---|
656 | and
|
---|
657 | .Dq ||
|
---|
658 | are AND-OR list operators.
|
---|
659 | .Dq \*[Am]\*[Am]
|
---|
660 | executes the first command, and then executes the second command if and only
|
---|
661 | if the exit status of the first command is zero.
|
---|
662 | .Dq ||
|
---|
663 | is similar, but executes the second command if and only if the exit status
|
---|
664 | of the first command is nonzero.
|
---|
665 | .Dq \*[Am]\*[Am]
|
---|
666 | and
|
---|
667 | .Dq ||
|
---|
668 | both have the same priority.
|
---|
669 | Note that these operators are left-associative, so
|
---|
670 | .Dq true || echo bar && echo baz
|
---|
671 | writes
|
---|
672 | .Dq baz
|
---|
673 | and nothing else.
|
---|
674 | This is not the way it works in C.
|
---|
675 | .Ss Flow-Control Constructs -- if, while, for, case
|
---|
676 | The syntax of the if command is
|
---|
677 | .Bd -literal -offset indent
|
---|
678 | if list
|
---|
679 | then list
|
---|
680 | [ elif list
|
---|
681 | then list ] ...
|
---|
682 | [ else list ]
|
---|
683 | fi
|
---|
684 | .Ed
|
---|
685 | .Pp
|
---|
686 | The syntax of the while command is
|
---|
687 | .Bd -literal -offset indent
|
---|
688 | while list
|
---|
689 | do list
|
---|
690 | done
|
---|
691 | .Ed
|
---|
692 | .Pp
|
---|
693 | The two lists are executed repeatedly while the exit status of the
|
---|
694 | first list is zero.
|
---|
695 | The until command is similar, but has the word
|
---|
696 | until in place of while, which causes it to
|
---|
697 | repeat until the exit status of the first list is zero.
|
---|
698 | .Pp
|
---|
699 | The syntax of the for command is
|
---|
700 | .Bd -literal -offset indent
|
---|
701 | for variable in word ...
|
---|
702 | do list
|
---|
703 | done
|
---|
704 | .Ed
|
---|
705 | .Pp
|
---|
706 | The words are expanded, and then the list is executed repeatedly with the
|
---|
707 | variable set to each word in turn.
|
---|
708 | do and done may be replaced with
|
---|
709 | .Dq {
|
---|
710 | and
|
---|
711 | .Dq } .
|
---|
712 | .Pp
|
---|
713 | The syntax of the break and continue command is
|
---|
714 | .Bd -literal -offset indent
|
---|
715 | break [ num ]
|
---|
716 | continue [ num ]
|
---|
717 | .Ed
|
---|
718 | .Pp
|
---|
719 | Break terminates the num innermost for or while loops.
|
---|
720 | Continue continues with the next iteration of the innermost loop.
|
---|
721 | These are implemented as builtin commands.
|
---|
722 | .Pp
|
---|
723 | The syntax of the case command is
|
---|
724 | .Bd -literal -offset indent
|
---|
725 | case word in
|
---|
726 | pattern) list ;;
|
---|
727 | \&...
|
---|
728 | esac
|
---|
729 | .Ed
|
---|
730 | .Pp
|
---|
731 | The pattern can actually be one or more patterns (see
|
---|
732 | .Sx Shell Patterns
|
---|
733 | described later), separated by
|
---|
734 | .Dq \*(Ba
|
---|
735 | characters.
|
---|
736 | .Ss Grouping Commands Together
|
---|
737 | Commands may be grouped by writing either
|
---|
738 | .Pp
|
---|
739 | .Dl (list)
|
---|
740 | .Pp
|
---|
741 | or
|
---|
742 | .Pp
|
---|
743 | .Dl { list; }
|
---|
744 | .Pp
|
---|
745 | The first of these executes the commands in a subshell.
|
---|
746 | Builtin commands grouped into a (list) will not affect the current shell.
|
---|
747 | The second form does not fork another shell so is slightly more efficient.
|
---|
748 | Grouping commands together this way allows you to redirect
|
---|
749 | their output as though they were one program:
|
---|
750 | .Pp
|
---|
751 | .Bd -literal -offset indent
|
---|
752 | { echo -n \*q hello \*q ; echo \*q world" ; } \*[Gt] greeting
|
---|
753 | .Ed
|
---|
754 | .Pp
|
---|
755 | Note that
|
---|
756 | .Dq }
|
---|
757 | must follow a control operator (here,
|
---|
758 | .Dq \&; )
|
---|
759 | so that it is recognized as a reserved word and not as another command argument.
|
---|
760 | .Ss Functions
|
---|
761 | The syntax of a function definition is
|
---|
762 | .Pp
|
---|
763 | .Dl name ( ) command
|
---|
764 | .Pp
|
---|
765 | A function definition is an executable statement; when executed it
|
---|
766 | installs a function named name and returns an exit status of zero.
|
---|
767 | The command is normally a list enclosed between
|
---|
768 | .Dq {
|
---|
769 | and
|
---|
770 | .Dq } .
|
---|
771 | .Pp
|
---|
772 | Variables may be declared to be local to a function by using a local
|
---|
773 | command.
|
---|
774 | This should appear as the first statement of a function, and the syntax is
|
---|
775 | .Pp
|
---|
776 | .Dl local [ variable | - ] ...
|
---|
777 | .Pp
|
---|
778 | Local is implemented as a builtin command.
|
---|
779 | .Pp
|
---|
780 | When a variable is made local, it inherits the initial value and exported
|
---|
781 | and readonly flags from the variable with the same name in the surrounding
|
---|
782 | scope, if there is one.
|
---|
783 | Otherwise, the variable is initially unset.
|
---|
784 | The shell uses dynamic scoping, so that if you make the variable x local to
|
---|
785 | function f, which then calls function g, references to the variable x made
|
---|
786 | inside g will refer to the variable x declared inside f, not to the global
|
---|
787 | variable named x.
|
---|
788 | .Pp
|
---|
789 | The only special parameter that can be made local is
|
---|
790 | .Dq - .
|
---|
791 | Making
|
---|
792 | .Dq -
|
---|
793 | local any shell options that are changed via the set command inside the
|
---|
794 | function to be restored to their original values when the function
|
---|
795 | returns.
|
---|
796 | .Pp
|
---|
797 | The syntax of the return command is
|
---|
798 | .Pp
|
---|
799 | .Dl return [ exitstatus ]
|
---|
800 | .Pp
|
---|
801 | It terminates the currently executing function.
|
---|
802 | Return is implemented as a builtin command.
|
---|
803 | .Ss Variables and Parameters
|
---|
804 | The shell maintains a set of parameters.
|
---|
805 | A parameter denoted by a name is called a variable.
|
---|
806 | When starting up, the shell turns all the environment
|
---|
807 | variables into shell variables.
|
---|
808 | New variables can be set using the form
|
---|
809 | .Pp
|
---|
810 | .Dl name=value
|
---|
811 | .Pp
|
---|
812 | Variables set by the user must have a name consisting solely of
|
---|
813 | alphabetics, numerics, and underscores - the first of which must not be
|
---|
814 | numeric.
|
---|
815 | A parameter can also be denoted by a number or a special
|
---|
816 | character as explained below.
|
---|
817 | .Ss Positional Parameters
|
---|
818 | A positional parameter is a parameter denoted by a number (n \*[Gt] 0).
|
---|
819 | The shell sets these initially to the values of its command line arguments
|
---|
820 | that follow the name of the shell script.
|
---|
821 | The
|
---|
822 | .Ic set
|
---|
823 | builtin can also be used to set or reset them.
|
---|
824 | .Ss Special Parameters
|
---|
825 | A special parameter is a parameter denoted by one of the following special
|
---|
826 | characters.
|
---|
827 | The value of the parameter is listed next to its character.
|
---|
828 | .Bl -tag -width thinhyphena
|
---|
829 | .It *
|
---|
830 | Expands to the positional parameters, starting from one.
|
---|
831 | When the
|
---|
832 | expansion occurs within a double-quoted string it expands to a single
|
---|
833 | field with the value of each parameter separated by the first character of
|
---|
834 | the
|
---|
835 | .Ev IFS
|
---|
836 | variable, or by a
|
---|
837 | .Aq space
|
---|
838 | if
|
---|
839 | .Ev IFS
|
---|
840 | is unset.
|
---|
841 | .It @
|
---|
842 | Expands to the positional parameters, starting from one.
|
---|
843 | When the expansion occurs within double-quotes, each positional
|
---|
844 | parameter expands as a separate argument.
|
---|
845 | If there are no positional parameters, the
|
---|
846 | expansion of @ generates zero arguments, even when @ is
|
---|
847 | double-quoted.
|
---|
848 | What this basically means, for example, is
|
---|
849 | if $1 is
|
---|
850 | .Dq abc
|
---|
851 | and $2 is
|
---|
852 | .Dq def ghi ,
|
---|
853 | then
|
---|
854 | .Qq $@
|
---|
855 | expands to
|
---|
856 | the two arguments:
|
---|
857 | .Pp
|
---|
858 | .Sm off
|
---|
859 | .Dl \*q abc \*q \ \*q def\ ghi \*q
|
---|
860 | .Sm on
|
---|
861 | .It #
|
---|
862 | Expands to the number of positional parameters.
|
---|
863 | .It \&?
|
---|
864 | Expands to the exit status of the most recent pipeline.
|
---|
865 | .It - (Hyphen.)
|
---|
866 | Expands to the current option flags (the single-letter
|
---|
867 | option names concatenated into a string) as specified on
|
---|
868 | invocation, by the set builtin command, or implicitly
|
---|
869 | by the shell.
|
---|
870 | .It $
|
---|
871 | Expands to the process ID of the invoked shell.
|
---|
872 | A subshell retains the same value of $ as its parent.
|
---|
873 | .It \&!
|
---|
874 | Expands to the process ID of the most recent background
|
---|
875 | command executed from the current shell.
|
---|
876 | For a pipeline, the process ID is that of the last command in the pipeline.
|
---|
877 | .It 0 (Zero.)
|
---|
878 | Expands to the name of the shell or shell script.
|
---|
879 | .El
|
---|
880 | .Ss Word Expansions
|
---|
881 | This clause describes the various expansions that are performed on words.
|
---|
882 | Not all expansions are performed on every word, as explained later.
|
---|
883 | .Pp
|
---|
884 | Tilde expansions, parameter expansions, command substitutions, arithmetic
|
---|
885 | expansions, and quote removals that occur within a single word expand to a
|
---|
886 | single field.
|
---|
887 | It is only field splitting or pathname expansion that can
|
---|
888 | create multiple fields from a single word.
|
---|
889 | The single exception to this
|
---|
890 | rule is the expansion of the special parameter @ within double-quotes, as
|
---|
891 | was described above.
|
---|
892 | .Pp
|
---|
893 | The order of word expansion is:
|
---|
894 | .Bl -enum
|
---|
895 | .It
|
---|
896 | Tilde Expansion, Parameter Expansion, Command Substitution,
|
---|
897 | Arithmetic Expansion (these all occur at the same time).
|
---|
898 | .It
|
---|
899 | Field Splitting is performed on fields
|
---|
900 | generated by step (1) unless the
|
---|
901 | .Ev IFS
|
---|
902 | variable is null.
|
---|
903 | .It
|
---|
904 | Pathname Expansion (unless set
|
---|
905 | .Fl f
|
---|
906 | is in effect).
|
---|
907 | .It
|
---|
908 | Quote Removal.
|
---|
909 | .El
|
---|
910 | .Pp
|
---|
911 | The $ character is used to introduce parameter expansion, command
|
---|
912 | substitution, or arithmetic evaluation.
|
---|
913 | .Ss Tilde Expansion (substituting a user's home directory)
|
---|
914 | A word beginning with an unquoted tilde character (~) is
|
---|
915 | subjected to tilde expansion.
|
---|
916 | All the characters up to
|
---|
917 | a slash (/) or the end of the word are treated as a username
|
---|
918 | and are replaced with the user's home directory.
|
---|
919 | If the username is missing (as in
|
---|
920 | .Pa ~/foobar ) ,
|
---|
921 | the tilde is replaced with the value of the
|
---|
922 | .Va HOME
|
---|
923 | variable (the current user's home directory).
|
---|
924 | .Ss Parameter Expansion
|
---|
925 | The format for parameter expansion is as follows:
|
---|
926 | .Pp
|
---|
927 | .Dl ${expression}
|
---|
928 | .Pp
|
---|
929 | where expression consists of all characters until the matching
|
---|
930 | .Dq } .
|
---|
931 | Any
|
---|
932 | .Dq }
|
---|
933 | escaped by a backslash or within a quoted string, and characters in
|
---|
934 | embedded arithmetic expansions, command substitutions, and variable
|
---|
935 | expansions, are not examined in determining the matching
|
---|
936 | .Dq } .
|
---|
937 | .Pp
|
---|
938 | The simplest form for parameter expansion is:
|
---|
939 | .Pp
|
---|
940 | .Dl ${parameter}
|
---|
941 | .Pp
|
---|
942 | The value, if any, of parameter is substituted.
|
---|
943 | .Pp
|
---|
944 | The parameter name or symbol can be enclosed in braces, which are
|
---|
945 | optional except for positional parameters with more than one digit or
|
---|
946 | when parameter is followed by a character that could be interpreted as
|
---|
947 | part of the name.
|
---|
948 | If a parameter expansion occurs inside double-quotes:
|
---|
949 | .Bl -enum
|
---|
950 | .It
|
---|
951 | Pathname expansion is not performed on the results of the expansion.
|
---|
952 | .It
|
---|
953 | Field splitting is not performed on the results of the
|
---|
954 | expansion, with the exception of the special rules for @.
|
---|
955 | .El
|
---|
956 | .Pp
|
---|
957 | In addition, a parameter expansion can be modified by using one of the
|
---|
958 | following formats.
|
---|
959 | .Bl -tag -width aaparameterwordaaaaa
|
---|
960 | .It ${parameter:-word}
|
---|
961 | Use Default Values.
|
---|
962 | If parameter is unset or null, the expansion of word
|
---|
963 | is substituted; otherwise, the value of parameter is substituted.
|
---|
964 | .It ${parameter:=word}
|
---|
965 | Assign Default Values.
|
---|
966 | If parameter is unset or null, the expansion of
|
---|
967 | word is assigned to parameter.
|
---|
968 | In all cases, the final value of parameter is substituted.
|
---|
969 | Only variables, not positional parameters or special
|
---|
970 | parameters, can be assigned in this way.
|
---|
971 | .It ${parameter:?[word]}
|
---|
972 | Indicate Error if Null or Unset.
|
---|
973 | If parameter is unset or null, the
|
---|
974 | expansion of word (or a message indicating it is unset if word is omitted)
|
---|
975 | is written to standard error and the shell exits with a nonzero exit status.
|
---|
976 | Otherwise, the value of parameter is substituted.
|
---|
977 | An interactive shell need not exit.
|
---|
978 | .It ${parameter:+word}
|
---|
979 | Use Alternative Value.
|
---|
980 | If parameter is unset or null, null is
|
---|
981 | substituted; otherwise, the expansion of word is substituted.
|
---|
982 | .El
|
---|
983 | .Pp
|
---|
984 | In the parameter expansions shown previously, use of the colon in the
|
---|
985 | format results in a test for a parameter that is unset or null; omission
|
---|
986 | of the colon results in a test for a parameter that is only unset.
|
---|
987 | .Bl -tag -width aaparameterwordaaaaa
|
---|
988 | .It ${#parameter}
|
---|
989 | String Length.
|
---|
990 | The length in characters of the value of parameter.
|
---|
991 | .El
|
---|
992 | .Pp
|
---|
993 | The following four varieties of parameter expansion provide for substring
|
---|
994 | processing.
|
---|
995 | In each case, pattern matching notation (see
|
---|
996 | .Sx Shell Patterns ) ,
|
---|
997 | rather than regular expression notation, is used to evaluate the patterns.
|
---|
998 | If parameter is * or @, the result of the expansion is unspecified.
|
---|
999 | Enclosing the full parameter expansion string in double-quotes does not
|
---|
1000 | cause the following four varieties of pattern characters to be quoted,
|
---|
1001 | whereas quoting characters within the braces has this effect.
|
---|
1002 | .Bl -tag -width aaparameterwordaaaaa
|
---|
1003 | .It ${parameter%word}
|
---|
1004 | Remove Smallest Suffix Pattern.
|
---|
1005 | The word is expanded to produce a pattern.
|
---|
1006 | The parameter expansion then results in parameter, with the
|
---|
1007 | smallest portion of the suffix matched by the pattern deleted.
|
---|
1008 | .It ${parameter%%word}
|
---|
1009 | Remove Largest Suffix Pattern.
|
---|
1010 | The word is expanded to produce a pattern.
|
---|
1011 | The parameter expansion then results in parameter, with the largest
|
---|
1012 | portion of the suffix matched by the pattern deleted.
|
---|
1013 | .It ${parameter#word}
|
---|
1014 | Remove Smallest Prefix Pattern.
|
---|
1015 | The word is expanded to produce a pattern.
|
---|
1016 | The parameter expansion then results in parameter, with the
|
---|
1017 | smallest portion of the prefix matched by the pattern deleted.
|
---|
1018 | .It ${parameter##word}
|
---|
1019 | Remove Largest Prefix Pattern.
|
---|
1020 | The word is expanded to produce a pattern.
|
---|
1021 | The parameter expansion then results in parameter, with the largest
|
---|
1022 | portion of the prefix matched by the pattern deleted.
|
---|
1023 | .El
|
---|
1024 | .Ss Command Substitution
|
---|
1025 | Command substitution allows the output of a command to be substituted in
|
---|
1026 | place of the command name itself.
|
---|
1027 | Command substitution occurs when the command is enclosed as follows:
|
---|
1028 | .Pp
|
---|
1029 | .Dl $(command)
|
---|
1030 | .Pp
|
---|
1031 | or
|
---|
1032 | .Po
|
---|
1033 | .Dq backquoted
|
---|
1034 | version
|
---|
1035 | .Pc :
|
---|
1036 | .Pp
|
---|
1037 | .Dl `command`
|
---|
1038 | .Pp
|
---|
1039 | The shell expands the command substitution by executing command in a
|
---|
1040 | subshell environment and replacing the command substitution with the
|
---|
1041 | standard output of the command, removing sequences of one or more
|
---|
1042 | .Ao newline Ac Ns s
|
---|
1043 | at the end of the substitution.
|
---|
1044 | (Embedded
|
---|
1045 | .Ao newline Ac Ns s
|
---|
1046 | before
|
---|
1047 | the end of the output are not removed; however, during field splitting,
|
---|
1048 | they may be translated into
|
---|
1049 | .Ao space Ac Ns s ,
|
---|
1050 | depending on the value of
|
---|
1051 | .Ev IFS
|
---|
1052 | and quoting that is in effect.)
|
---|
1053 | .Ss Arithmetic Expansion
|
---|
1054 | Arithmetic expansion provides a mechanism for evaluating an arithmetic
|
---|
1055 | expression and substituting its value.
|
---|
1056 | The format for arithmetic expansion is as follows:
|
---|
1057 | .Pp
|
---|
1058 | .Dl $((expression))
|
---|
1059 | .Pp
|
---|
1060 | The expression is treated as if it were in double-quotes, except
|
---|
1061 | that a double-quote inside the expression is not treated specially.
|
---|
1062 | The shell expands all tokens in the expression for parameter expansion,
|
---|
1063 | command substitution, and quote removal.
|
---|
1064 | .Pp
|
---|
1065 | Next, the shell treats this as an arithmetic expression and
|
---|
1066 | substitutes the value of the expression.
|
---|
1067 | .Ss White Space Splitting (Field Splitting)
|
---|
1068 | After parameter expansion, command substitution, and
|
---|
1069 | arithmetic expansion the shell scans the results of
|
---|
1070 | expansions and substitutions that did not occur in double-quotes for
|
---|
1071 | field splitting and multiple fields can result.
|
---|
1072 | .Pp
|
---|
1073 | The shell treats each character of the
|
---|
1074 | .Ev IFS
|
---|
1075 | as a delimiter and use the delimiters to split the results of parameter
|
---|
1076 | expansion and command substitution into fields.
|
---|
1077 | .Pp
|
---|
1078 | Non-whitespace characters in
|
---|
1079 | .Ev IFS
|
---|
1080 | are treated strictly as parameter terminators.
|
---|
1081 | So adjacent non-whitespace
|
---|
1082 | .Ev IFS
|
---|
1083 | characters will produce empty parameters.
|
---|
1084 | .Pp
|
---|
1085 | If
|
---|
1086 | .Ev IFS
|
---|
1087 | is unset it is assumed to contain space, tab, and newline.
|
---|
1088 | .Ss Pathname Expansion (File Name Generation)
|
---|
1089 | Unless the
|
---|
1090 | .Fl f
|
---|
1091 | flag is set, file name generation is performed after word splitting is
|
---|
1092 | complete.
|
---|
1093 | Each word is viewed as a series of patterns, separated by slashes.
|
---|
1094 | The process of expansion replaces the word with the names of all
|
---|
1095 | existing files whose names can be formed by replacing each pattern with a
|
---|
1096 | string that matches the specified pattern.
|
---|
1097 | There are two restrictions on
|
---|
1098 | this: first, a pattern cannot match a string containing a slash, and
|
---|
1099 | second, a pattern cannot match a string starting with a period unless the
|
---|
1100 | first character of the pattern is a period.
|
---|
1101 | The next section describes the
|
---|
1102 | patterns used for both Pathname Expansion and the
|
---|
1103 | .Ic case
|
---|
1104 | command.
|
---|
1105 | .Ss Shell Patterns
|
---|
1106 | A pattern consists of normal characters, which match themselves,
|
---|
1107 | and meta-characters.
|
---|
1108 | The meta-characters are
|
---|
1109 | .Dq \&! ,
|
---|
1110 | .Dq * ,
|
---|
1111 | .Dq \&? ,
|
---|
1112 | and
|
---|
1113 | .Dq \&[ .
|
---|
1114 | These characters lose their special meanings if they are quoted.
|
---|
1115 | When command or variable substitution is performed
|
---|
1116 | and the dollar sign or back quotes are not double quoted,
|
---|
1117 | the value of the variable or the output of
|
---|
1118 | the command is scanned for these characters and they are turned into
|
---|
1119 | meta-characters.
|
---|
1120 | .Pp
|
---|
1121 | An asterisk
|
---|
1122 | .Pq Dq *
|
---|
1123 | matches any string of characters.
|
---|
1124 | A question mark matches any single character.
|
---|
1125 | A left bracket
|
---|
1126 | .Pq Dq \&[
|
---|
1127 | introduces a character class.
|
---|
1128 | The end of the character class is indicated by a
|
---|
1129 | .Pq Dq \&] ;
|
---|
1130 | if the
|
---|
1131 | .Dq \&]
|
---|
1132 | is missing then the
|
---|
1133 | .Dq \&[
|
---|
1134 | matches a
|
---|
1135 | .Dq \&[
|
---|
1136 | rather than introducing a character class.
|
---|
1137 | A character class matches any of the characters between the square brackets.
|
---|
1138 | A range of characters may be specified using a minus sign.
|
---|
1139 | The character class may be complemented
|
---|
1140 | by making an exclamation point the first character of the character class.
|
---|
1141 | .Pp
|
---|
1142 | To include a
|
---|
1143 | .Dq \&]
|
---|
1144 | in a character class, make it the first character listed (after the
|
---|
1145 | .Dq \&! ,
|
---|
1146 | if any).
|
---|
1147 | To include a minus sign, make it the first or last character listed.
|
---|
1148 | .Ss Builtins
|
---|
1149 | This section lists the builtin commands which are builtin because they
|
---|
1150 | need to perform some operation that can't be performed by a separate
|
---|
1151 | process.
|
---|
1152 | In addition to these, there are several other commands that may
|
---|
1153 | be builtin for efficiency (e.g.
|
---|
1154 | .Xr printf 1 ,
|
---|
1155 | .Xr echo 1 ,
|
---|
1156 | .Xr test 1 ,
|
---|
1157 | etc).
|
---|
1158 | .Bl -tag -width 5n
|
---|
1159 | .It :
|
---|
1160 | A null command that returns a 0 (true) exit value.
|
---|
1161 | .It \&. file
|
---|
1162 | The commands in the specified file are read and executed by the shell.
|
---|
1163 | .It alias Op Ar name Ns Op Ar "=string ..."
|
---|
1164 | If
|
---|
1165 | .Ar name=string
|
---|
1166 | is specified, the shell defines the alias
|
---|
1167 | .Ar name
|
---|
1168 | with value
|
---|
1169 | .Ar string .
|
---|
1170 | If just
|
---|
1171 | .Ar name
|
---|
1172 | is specified, the value of the alias
|
---|
1173 | .Ar name
|
---|
1174 | is printed.
|
---|
1175 | With no arguments, the
|
---|
1176 | .Ic alias
|
---|
1177 | builtin prints the
|
---|
1178 | names and values of all defined aliases (see
|
---|
1179 | .Ic unalias ) .
|
---|
1180 | .It bg [ Ar job ] ...
|
---|
1181 | Continue the specified jobs (or the current job if no
|
---|
1182 | jobs are given) in the background.
|
---|
1183 | .It Xo command
|
---|
1184 | .Op Fl p
|
---|
1185 | .Op Fl v
|
---|
1186 | .Op Fl V
|
---|
1187 | .Ar command
|
---|
1188 | .Op Ar arg ...
|
---|
1189 | .Xc
|
---|
1190 | Execute the specified command but ignore shell functions when searching
|
---|
1191 | for it.
|
---|
1192 | (This is useful when you
|
---|
1193 | have a shell function with the same name as a builtin command.)
|
---|
1194 | .Bl -tag -width 5n
|
---|
1195 | .It Fl p
|
---|
1196 | search for command using a
|
---|
1197 | .Ev PATH
|
---|
1198 | that guarantees to find all the standard utilities.
|
---|
1199 | .It Fl V
|
---|
1200 | Do not execute the command but
|
---|
1201 | search for the command and print the resolution of the
|
---|
1202 | command search.
|
---|
1203 | This is the same as the type builtin.
|
---|
1204 | .It Fl v
|
---|
1205 | Do not execute the command but
|
---|
1206 | search for the command and print the absolute pathname
|
---|
1207 | of utilities, the name for builtins or the expansion of aliases.
|
---|
1208 | .El
|
---|
1209 | .It cd Op Ar directory Op Ar replace
|
---|
1210 | Switch to the specified directory (default
|
---|
1211 | .Ev $HOME ) .
|
---|
1212 | If
|
---|
1213 | .Ar replace
|
---|
1214 | is specified, then the new directory name is generated by replacing
|
---|
1215 | the first occurrence of
|
---|
1216 | .Ar directory
|
---|
1217 | in the current directory name with
|
---|
1218 | .Ar replace .
|
---|
1219 | Otherwise if an entry for
|
---|
1220 | .Ev CDPATH
|
---|
1221 | appears in the environment of the
|
---|
1222 | .Ic cd
|
---|
1223 | command or the shell variable
|
---|
1224 | .Ev CDPATH
|
---|
1225 | is set and the directory name does not begin with a slash, then the
|
---|
1226 | directories listed in
|
---|
1227 | .Ev CDPATH
|
---|
1228 | will be searched for the specified directory.
|
---|
1229 | The format of
|
---|
1230 | .Ev CDPATH
|
---|
1231 | is the same as that of
|
---|
1232 | .Ev PATH .
|
---|
1233 | In an interactive shell, the
|
---|
1234 | .Ic cd
|
---|
1235 | command will print out the name of the
|
---|
1236 | directory that it actually switched to if this is different from the name
|
---|
1237 | that the user gave.
|
---|
1238 | These may be different either because the
|
---|
1239 | .Ev CDPATH
|
---|
1240 | mechanism was used or because a symbolic link was crossed.
|
---|
1241 | .It eval Ar string ...
|
---|
1242 | Concatenate all the arguments with spaces.
|
---|
1243 | Then re-parse and execute the command.
|
---|
1244 | .It exec Op Ar command arg ...
|
---|
1245 | Unless command is omitted, the shell process is replaced with the
|
---|
1246 | specified program (which must be a real program, not a shell builtin or
|
---|
1247 | function).
|
---|
1248 | Any redirections on the
|
---|
1249 | .Ic exec
|
---|
1250 | command are marked as permanent, so that they are not undone when the
|
---|
1251 | .Ic exec
|
---|
1252 | command finishes.
|
---|
1253 | .It exit Op Ar exitstatus
|
---|
1254 | Terminate the shell process.
|
---|
1255 | If
|
---|
1256 | .Ar exitstatus
|
---|
1257 | is given it is used as the exit status of the shell; otherwise the
|
---|
1258 | exit status of the preceding command is used.
|
---|
1259 | .It export Ar name ...
|
---|
1260 | .It export Fl p
|
---|
1261 | The specified names are exported so that they will appear in the
|
---|
1262 | environment of subsequent commands.
|
---|
1263 | The only way to un-export a variable is to unset it.
|
---|
1264 | The shell allows the value of a variable to be set at the
|
---|
1265 | same time it is exported by writing
|
---|
1266 | .Pp
|
---|
1267 | .Dl export name=value
|
---|
1268 | .Pp
|
---|
1269 | With no arguments the export command lists the names of all exported variables.
|
---|
1270 | With the
|
---|
1271 | .Fl p
|
---|
1272 | option specified the output will be formatted suitably for non-interactive use.
|
---|
1273 | .It Xo fc Op Fl e Ar editor
|
---|
1274 | .Op Ar first Op Ar last
|
---|
1275 | .Xc
|
---|
1276 | .It Xo fc Fl l
|
---|
1277 | .Op Fl nr
|
---|
1278 | .Op Ar first Op Ar last
|
---|
1279 | .Xc
|
---|
1280 | .It Xo fc Fl s Op Ar old=new
|
---|
1281 | .Op Ar first
|
---|
1282 | .Xc
|
---|
1283 | The
|
---|
1284 | .Ic fc
|
---|
1285 | builtin lists, or edits and re-executes, commands previously entered
|
---|
1286 | to an interactive shell.
|
---|
1287 | .Bl -tag -width 5n
|
---|
1288 | .It Fl e No editor
|
---|
1289 | Use the editor named by editor to edit the commands.
|
---|
1290 | The editor string is a command name, subject to search via the
|
---|
1291 | .Ev PATH
|
---|
1292 | variable.
|
---|
1293 | The value in the
|
---|
1294 | .Ev FCEDIT
|
---|
1295 | variable is used as a default when
|
---|
1296 | .Fl e
|
---|
1297 | is not specified.
|
---|
1298 | If
|
---|
1299 | .Ev FCEDIT
|
---|
1300 | is null or unset, the value of the
|
---|
1301 | .Ev EDITOR
|
---|
1302 | variable is used.
|
---|
1303 | If
|
---|
1304 | .Ev EDITOR
|
---|
1305 | is null or unset,
|
---|
1306 | .Xr ed 1
|
---|
1307 | is used as the editor.
|
---|
1308 | .It Fl l No (ell)
|
---|
1309 | List the commands rather than invoking an editor on them.
|
---|
1310 | The commands are written in the sequence indicated by
|
---|
1311 | the first and last operands, as affected by
|
---|
1312 | .Fl r ,
|
---|
1313 | with each command preceded by the command number.
|
---|
1314 | .It Fl n
|
---|
1315 | Suppress command numbers when listing with -l.
|
---|
1316 | .It Fl r
|
---|
1317 | Reverse the order of the commands listed (with
|
---|
1318 | .Fl l )
|
---|
1319 | or edited (with neither
|
---|
1320 | .Fl l
|
---|
1321 | nor
|
---|
1322 | .Fl s ) .
|
---|
1323 | .It Fl s
|
---|
1324 | Re-execute the command without invoking an editor.
|
---|
1325 | .It first
|
---|
1326 | .It last
|
---|
1327 | Select the commands to list or edit.
|
---|
1328 | The number of previous commands that
|
---|
1329 | can be accessed are determined by the value of the
|
---|
1330 | .Ev HISTSIZE
|
---|
1331 | variable.
|
---|
1332 | The value of first or last or both are one of the following:
|
---|
1333 | .Bl -tag -width 5n
|
---|
1334 | .It [+]number
|
---|
1335 | A positive number representing a command number; command numbers can be
|
---|
1336 | displayed with the
|
---|
1337 | .Fl l
|
---|
1338 | option.
|
---|
1339 | .It Fl number
|
---|
1340 | A negative decimal number representing the command that was executed
|
---|
1341 | number of commands previously.
|
---|
1342 | For example, \-1 is the immediately previous command.
|
---|
1343 | .El
|
---|
1344 | .It string
|
---|
1345 | A string indicating the most recently entered command that begins with
|
---|
1346 | that string.
|
---|
1347 | If the old=new operand is not also specified with
|
---|
1348 | .Fl s ,
|
---|
1349 | the string form of the first operand cannot contain an embedded equal sign.
|
---|
1350 | .El
|
---|
1351 | .Pp
|
---|
1352 | The following environment variables affect the execution of fc:
|
---|
1353 | .Bl -tag -width HISTSIZE
|
---|
1354 | .It Ev FCEDIT
|
---|
1355 | Name of the editor to use.
|
---|
1356 | .It Ev HISTSIZE
|
---|
1357 | The number of previous commands that are accessible.
|
---|
1358 | .El
|
---|
1359 | .It fg Op Ar job
|
---|
1360 | Move the specified job or the current job to the foreground.
|
---|
1361 | .It getopts Ar optstring var
|
---|
1362 | The
|
---|
1363 | .Tn POSIX
|
---|
1364 | .Ic getopts
|
---|
1365 | command, not to be confused with the
|
---|
1366 | .Em Bell Labs
|
---|
1367 | -derived
|
---|
1368 | .Xr getopt 1 .
|
---|
1369 | .Pp
|
---|
1370 | The first argument should be a series of letters, each of which may be
|
---|
1371 | optionally followed by a colon to indicate that the option requires an
|
---|
1372 | argument.
|
---|
1373 | The variable specified is set to the parsed option.
|
---|
1374 | .Pp
|
---|
1375 | The
|
---|
1376 | .Ic getopts
|
---|
1377 | command deprecates the older
|
---|
1378 | .Xr getopt 1
|
---|
1379 | utility due to its handling of arguments containing whitespace.
|
---|
1380 | .Pp
|
---|
1381 | The
|
---|
1382 | .Ic getopts
|
---|
1383 | builtin may be used to obtain options and their arguments
|
---|
1384 | from a list of parameters.
|
---|
1385 | When invoked,
|
---|
1386 | .Ic getopts
|
---|
1387 | places the value of the next option from the option string in the list in
|
---|
1388 | the shell variable specified by
|
---|
1389 | .Va var
|
---|
1390 | and its index in the shell variable
|
---|
1391 | .Ev OPTIND .
|
---|
1392 | When the shell is invoked,
|
---|
1393 | .Ev OPTIND
|
---|
1394 | is initialized to 1.
|
---|
1395 | For each option that requires an argument, the
|
---|
1396 | .Ic getopts
|
---|
1397 | builtin will place it in the shell variable
|
---|
1398 | .Ev OPTARG .
|
---|
1399 | If an option is not allowed for in the
|
---|
1400 | .Va optstring ,
|
---|
1401 | then
|
---|
1402 | .Ev OPTARG
|
---|
1403 | will be unset.
|
---|
1404 | .Pp
|
---|
1405 | .Va optstring
|
---|
1406 | is a string of recognized option letters (see
|
---|
1407 | .Xr getopt 3 ) .
|
---|
1408 | If a letter is followed by a colon, the option is expected to have an
|
---|
1409 | argument which may or may not be separated from it by whitespace.
|
---|
1410 | If an option character is not found where expected,
|
---|
1411 | .Ic getopts
|
---|
1412 | will set the variable
|
---|
1413 | .Va var
|
---|
1414 | to a
|
---|
1415 | .Dq \&? ;
|
---|
1416 | .Ic getopts
|
---|
1417 | will then unset
|
---|
1418 | .Ev OPTARG
|
---|
1419 | and write output to standard error.
|
---|
1420 | By specifying a colon as the first character of
|
---|
1421 | .Va optstring
|
---|
1422 | all errors will be ignored.
|
---|
1423 | .Pp
|
---|
1424 | A nonzero value is returned when the last option is reached.
|
---|
1425 | If there are no remaining arguments,
|
---|
1426 | .Ic getopts
|
---|
1427 | will set
|
---|
1428 | .Va var
|
---|
1429 | to the special option,
|
---|
1430 | .Dq -- ,
|
---|
1431 | otherwise, it will set
|
---|
1432 | .Va var
|
---|
1433 | to
|
---|
1434 | .Dq \&? .
|
---|
1435 | .Pp
|
---|
1436 | The following code fragment shows how one might process the arguments
|
---|
1437 | for a command that can take the options
|
---|
1438 | .Op a
|
---|
1439 | and
|
---|
1440 | .Op b ,
|
---|
1441 | and the option
|
---|
1442 | .Op c ,
|
---|
1443 | which requires an argument.
|
---|
1444 | .Pp
|
---|
1445 | .Bd -literal -offset indent
|
---|
1446 | while getopts abc: f
|
---|
1447 | do
|
---|
1448 | case $f in
|
---|
1449 | a | b) flag=$f;;
|
---|
1450 | c) carg=$OPTARG;;
|
---|
1451 | \\?) echo $USAGE; exit 1;;
|
---|
1452 | esac
|
---|
1453 | done
|
---|
1454 | shift `expr $OPTIND - 1`
|
---|
1455 | .Ed
|
---|
1456 | .Pp
|
---|
1457 | This code will accept any of the following as equivalent:
|
---|
1458 | .Pp
|
---|
1459 | .Bd -literal -offset indent
|
---|
1460 | cmd \-acarg file file
|
---|
1461 | cmd \-a \-c arg file file
|
---|
1462 | cmd \-carg -a file file
|
---|
1463 | cmd \-a \-carg \-\- file file
|
---|
1464 | .Ed
|
---|
1465 | .It hash Fl rv Ar command ...
|
---|
1466 | The shell maintains a hash table which remembers the
|
---|
1467 | locations of commands.
|
---|
1468 | With no arguments whatsoever,
|
---|
1469 | the
|
---|
1470 | .Ic hash
|
---|
1471 | command prints out the contents of this table.
|
---|
1472 | Entries which have not been looked at since the last
|
---|
1473 | .Ic cd
|
---|
1474 | command are marked with an asterisk; it is possible for these entries
|
---|
1475 | to be invalid.
|
---|
1476 | .Pp
|
---|
1477 | With arguments, the
|
---|
1478 | .Ic hash
|
---|
1479 | command removes the specified commands from the hash table (unless
|
---|
1480 | they are functions) and then locates them.
|
---|
1481 | With the
|
---|
1482 | .Fl v
|
---|
1483 | option, hash prints the locations of the commands as it finds them.
|
---|
1484 | The
|
---|
1485 | .Fl r
|
---|
1486 | option causes the hash command to delete all the entries in the hash table
|
---|
1487 | except for functions.
|
---|
1488 | .It inputrc Ar file
|
---|
1489 | Read the
|
---|
1490 | .Va file
|
---|
1491 | to set keybindings as defined by
|
---|
1492 | .Xr editrc 5 .
|
---|
1493 | .It jobid Op Ar job
|
---|
1494 | Print the process id's of the processes in the job.
|
---|
1495 | If the
|
---|
1496 | .Ar job
|
---|
1497 | argument is omitted, the current job is used.
|
---|
1498 | .It jobs
|
---|
1499 | This command lists out all the background processes
|
---|
1500 | which are children of the current shell process.
|
---|
1501 | .It pwd Op Fl LP
|
---|
1502 | Print the current directory.
|
---|
1503 | If
|
---|
1504 | .Fl L
|
---|
1505 | is specified the cached value (initially set from
|
---|
1506 | .Ev PWD )
|
---|
1507 | is checked to see if it refers to the current directory, if it does
|
---|
1508 | the value is printed.
|
---|
1509 | Otherwise the current directory name is found using
|
---|
1510 | .Xr getcwd(3) .
|
---|
1511 | The environment variable
|
---|
1512 | .Ev PWD
|
---|
1513 | is set to printed value.
|
---|
1514 | .Pp
|
---|
1515 | The default is
|
---|
1516 | .Ic pwd
|
---|
1517 | .Fl L ,
|
---|
1518 | but note that the builtin
|
---|
1519 | .Ic cd
|
---|
1520 | command doesn't currently support
|
---|
1521 | .Fl L
|
---|
1522 | or
|
---|
1523 | .Fl P
|
---|
1524 | and will cache (almost) the absolute path.
|
---|
1525 | If
|
---|
1526 | .Ic cd
|
---|
1527 | is changed,
|
---|
1528 | .Ic pwd
|
---|
1529 | may be changed to default to
|
---|
1530 | .Ic pwd
|
---|
1531 | .Fl P .
|
---|
1532 | .Pp
|
---|
1533 | If the current directory is renamed and replaced by a symlink to the
|
---|
1534 | same directory, or the initial
|
---|
1535 | .Ev PWD
|
---|
1536 | value followed a symbolic link, then the cached value may not
|
---|
1537 | be the absolute path.
|
---|
1538 | .Pp
|
---|
1539 | The builtin command may differ from the program of the same name because
|
---|
1540 | the program will use
|
---|
1541 | .Ev PWD
|
---|
1542 | and the builtin uses a separately cached value.
|
---|
1543 | .It Xo read Op Fl p Ar prompt
|
---|
1544 | .Op Fl r
|
---|
1545 | .Ar variable
|
---|
1546 | .Op Ar ...
|
---|
1547 | .Xc
|
---|
1548 | The prompt is printed if the
|
---|
1549 | .Fl p
|
---|
1550 | option is specified and the standard input is a terminal.
|
---|
1551 | Then a line is read from the standard input.
|
---|
1552 | The trailing newline is deleted from the
|
---|
1553 | line and the line is split as described in the section on word splitting
|
---|
1554 | above, and the pieces are assigned to the variables in order.
|
---|
1555 | If there are more pieces than variables, the remaining pieces
|
---|
1556 | (along with the characters in
|
---|
1557 | .Ev IFS
|
---|
1558 | that separated them) are assigned to the last variable.
|
---|
1559 | If there are more variables than pieces,
|
---|
1560 | the remaining variables are assigned the null string.
|
---|
1561 | The
|
---|
1562 | .Ic read
|
---|
1563 | builtin will indicate success unless EOF is encountered on input, in
|
---|
1564 | which case failure is returned.
|
---|
1565 | .Pp
|
---|
1566 | By default, unless the
|
---|
1567 | .Fl r
|
---|
1568 | option is specified, the backslash
|
---|
1569 | .Dq \e
|
---|
1570 | acts as an escape character, causing the following character to be treated
|
---|
1571 | literally.
|
---|
1572 | If a backslash is followed by a newline, the backslash and the
|
---|
1573 | newline will be deleted.
|
---|
1574 | .It readonly Ar name ...
|
---|
1575 | .It readonly Fl p
|
---|
1576 | The specified names are marked as read only, so that they cannot be
|
---|
1577 | subsequently modified or unset.
|
---|
1578 | The shell allows the value of a variable
|
---|
1579 | to be set at the same time it is marked read only by writing
|
---|
1580 | .Pp
|
---|
1581 | .Dl readonly name=value
|
---|
1582 | .Pp
|
---|
1583 | With no arguments the readonly command lists the names of all read only
|
---|
1584 | variables.
|
---|
1585 | With the
|
---|
1586 | .Fl p
|
---|
1587 | option specified the output will be formatted suitably for non-interactive use.
|
---|
1588 | .Pp
|
---|
1589 | .It Xo set
|
---|
1590 | .Oo {
|
---|
1591 | .Fl options | Cm +options | Cm -- }
|
---|
1592 | .Oc Ar arg ...
|
---|
1593 | .Xc
|
---|
1594 | The
|
---|
1595 | .Ic set
|
---|
1596 | command performs three different functions.
|
---|
1597 | .Pp
|
---|
1598 | With no arguments, it lists the values of all shell variables.
|
---|
1599 | .Pp
|
---|
1600 | If options are given, it sets the specified option
|
---|
1601 | flags, or clears them as described in the section called
|
---|
1602 | .Sx Argument List Processing .
|
---|
1603 | .Pp
|
---|
1604 | The third use of the set command is to set the values of the shell's
|
---|
1605 | positional parameters to the specified args.
|
---|
1606 | To change the positional
|
---|
1607 | parameters without changing any options, use
|
---|
1608 | .Dq --
|
---|
1609 | as the first argument to set.
|
---|
1610 | If no args are present, the set command
|
---|
1611 | will clear all the positional parameters (equivalent to executing
|
---|
1612 | .Dq shift $# . )
|
---|
1613 | .It setvar Ar variable Ar value
|
---|
1614 | Assigns value to variable.
|
---|
1615 | (In general it is better to write
|
---|
1616 | variable=value rather than using
|
---|
1617 | .Ic setvar .
|
---|
1618 | .Ic setvar
|
---|
1619 | is intended to be used in
|
---|
1620 | functions that assign values to variables whose names are passed as
|
---|
1621 | parameters.)
|
---|
1622 | .It shift Op Ar n
|
---|
1623 | Shift the positional parameters n times.
|
---|
1624 | A
|
---|
1625 | .Ic shift
|
---|
1626 | sets the value of
|
---|
1627 | .Va $1
|
---|
1628 | to the value of
|
---|
1629 | .Va $2 ,
|
---|
1630 | the value of
|
---|
1631 | .Va $2
|
---|
1632 | to the value of
|
---|
1633 | .Va $3 ,
|
---|
1634 | and so on, decreasing
|
---|
1635 | the value of
|
---|
1636 | .Va $#
|
---|
1637 | by one.
|
---|
1638 | If there are zero positional parameters,
|
---|
1639 | .Ic shift
|
---|
1640 | does nothing.
|
---|
1641 | .It Xo trap
|
---|
1642 | .Op Fl l
|
---|
1643 | .Xc
|
---|
1644 | .It Xo trap
|
---|
1645 | .Op Ar action
|
---|
1646 | .Ar signal ...
|
---|
1647 | .Xc
|
---|
1648 | Cause the shell to parse and execute action when any of the specified
|
---|
1649 | signals are received.
|
---|
1650 | The signals are specified by signal number or as the name of the signal.
|
---|
1651 | If
|
---|
1652 | .Ar signal
|
---|
1653 | is
|
---|
1654 | .Li 0 ,
|
---|
1655 | the action is executed when the shell exits.
|
---|
1656 | .Ar action
|
---|
1657 | may be null, which cause the specified signals to be ignored.
|
---|
1658 | With
|
---|
1659 | .Ar action
|
---|
1660 | omitted or set to `-' the specified signals are set to their default action.
|
---|
1661 | When the shell forks off a subshell, it resets trapped (but not ignored)
|
---|
1662 | signals to the default action.
|
---|
1663 | The
|
---|
1664 | .Ic trap
|
---|
1665 | command has no effect on signals that were
|
---|
1666 | ignored on entry to the shell.
|
---|
1667 | Issuing
|
---|
1668 | .Ic trap
|
---|
1669 | with option
|
---|
1670 | .Ar -l
|
---|
1671 | will print a list of valid signal names.
|
---|
1672 | .Ic trap
|
---|
1673 | without any arguments cause it to write a list of signals and their
|
---|
1674 | associated action to the standard output in a format that is suitable
|
---|
1675 | as an input to the shell that achieves the same trapping results.
|
---|
1676 | .Pp
|
---|
1677 | Examples:
|
---|
1678 | .Pp
|
---|
1679 | .Dl trap
|
---|
1680 | .Pp
|
---|
1681 | List trapped signals and their corresponding action
|
---|
1682 | .Pp
|
---|
1683 | .Dl trap -l
|
---|
1684 | .Pp
|
---|
1685 | Print a list of valid signals
|
---|
1686 | .Pp
|
---|
1687 | .Dl trap '' INT QUIT tstp 30
|
---|
1688 | .Pp
|
---|
1689 | Ignore signals INT QUIT TSTP USR1
|
---|
1690 | .Pp
|
---|
1691 | .Dl trap date INT
|
---|
1692 | .Pp
|
---|
1693 | Print date upon receiving signal INT
|
---|
1694 | .It type Op Ar name ...
|
---|
1695 | Interpret each name as a command and print the resolution of the command
|
---|
1696 | search.
|
---|
1697 | Possible resolutions are:
|
---|
1698 | shell keyword, alias, shell builtin,
|
---|
1699 | command, tracked alias and not found.
|
---|
1700 | For aliases the alias expansion is
|
---|
1701 | printed; for commands and tracked aliases the complete pathname of the
|
---|
1702 | command is printed.
|
---|
1703 | .It ulimit Xo
|
---|
1704 | .Op Fl H \*(Ba Fl S
|
---|
1705 | .Op Fl a \*(Ba Fl tfdscmlpn Op Ar value
|
---|
1706 | .Xc
|
---|
1707 | Inquire about or set the hard or soft limits on processes or set new
|
---|
1708 | limits.
|
---|
1709 | The choice between hard limit (which no process is allowed to
|
---|
1710 | violate, and which may not be raised once it has been lowered) and soft
|
---|
1711 | limit (which causes processes to be signaled but not necessarily killed,
|
---|
1712 | and which may be raised) is made with these flags:
|
---|
1713 | .Bl -tag -width Fl
|
---|
1714 | .It Fl H
|
---|
1715 | set or inquire about hard limits
|
---|
1716 | .It Fl S
|
---|
1717 | set or inquire about soft limits.
|
---|
1718 | If neither
|
---|
1719 | .Fl H
|
---|
1720 | nor
|
---|
1721 | .Fl S
|
---|
1722 | is specified, the soft limit is displayed or both limits are set.
|
---|
1723 | If both are specified, the last one wins.
|
---|
1724 | .El
|
---|
1725 | .Pp
|
---|
1726 | .Bl -tag -width Fl
|
---|
1727 | The limit to be interrogated or set, then, is chosen by specifying
|
---|
1728 | any one of these flags:
|
---|
1729 | .It Fl a
|
---|
1730 | show all the current limits
|
---|
1731 | .It Fl b
|
---|
1732 | show or set the limit on the socket buffer size of a process (in bytes)
|
---|
1733 | .It Fl t
|
---|
1734 | show or set the limit on CPU time (in seconds)
|
---|
1735 | .It Fl f
|
---|
1736 | show or set the limit on the largest file that can be created
|
---|
1737 | (in 512-byte blocks)
|
---|
1738 | .It Fl d
|
---|
1739 | show or set the limit on the data segment size of a process (in kilobytes)
|
---|
1740 | .It Fl s
|
---|
1741 | show or set the limit on the stack size of a process (in kilobytes)
|
---|
1742 | .It Fl c
|
---|
1743 | show or set the limit on the largest core dump size that can be produced
|
---|
1744 | (in 512-byte blocks)
|
---|
1745 | .It Fl m
|
---|
1746 | show or set the limit on the total physical memory that can be
|
---|
1747 | in use by a process (in kilobytes)
|
---|
1748 | .It Fl l
|
---|
1749 | show or set the limit on how much memory a process can lock with
|
---|
1750 | .Xr mlock 2
|
---|
1751 | (in kilobytes)
|
---|
1752 | .It Fl p
|
---|
1753 | show or set the limit on the number of processes this user can
|
---|
1754 | have at one time
|
---|
1755 | .It Fl n
|
---|
1756 | show or set the limit on the number of files a process can have open at once
|
---|
1757 | .El
|
---|
1758 | .Pp
|
---|
1759 | If none of these is specified, it is the limit on file size that is shown
|
---|
1760 | or set.
|
---|
1761 | If value is specified, the limit is set to that number; otherwise
|
---|
1762 | the current limit is displayed.
|
---|
1763 | .Pp
|
---|
1764 | Limits of an arbitrary process can be displayed or set using the
|
---|
1765 | .Xr sysctl 8
|
---|
1766 | utility.
|
---|
1767 | .Pp
|
---|
1768 | .It umask Op Ar mask
|
---|
1769 | Set the value of umask (see
|
---|
1770 | .Xr umask 2 )
|
---|
1771 | to the specified octal value.
|
---|
1772 | If the argument is omitted, the umask value is printed.
|
---|
1773 | .It unalias Xo
|
---|
1774 | .Op Fl a
|
---|
1775 | .Op Ar name
|
---|
1776 | .Xc
|
---|
1777 | If
|
---|
1778 | .Ar name
|
---|
1779 | is specified, the shell removes that alias.
|
---|
1780 | If
|
---|
1781 | .Fl a
|
---|
1782 | is specified, all aliases are removed.
|
---|
1783 | .It unset Ar name ...
|
---|
1784 | The specified variables and functions are unset and unexported.
|
---|
1785 | If a given name corresponds to both a variable and a function, both
|
---|
1786 | the variable and the function are unset.
|
---|
1787 | .It wait Op Ar job
|
---|
1788 | Wait for the specified job to complete and return the exit status of the
|
---|
1789 | last process in the job.
|
---|
1790 | If the argument is omitted, wait for all jobs to
|
---|
1791 | complete and then return an exit status of zero.
|
---|
1792 | .El
|
---|
1793 | .Ss Command Line Editing
|
---|
1794 | When
|
---|
1795 | .Nm
|
---|
1796 | is being used interactively from a terminal, the current command
|
---|
1797 | and the command history (see
|
---|
1798 | .Ic fc
|
---|
1799 | in
|
---|
1800 | .Sx Builtins )
|
---|
1801 | can be edited using emacs-mode or vi-mode command-line editing.
|
---|
1802 | The command
|
---|
1803 | .Ql set -o emacs
|
---|
1804 | enables emacs-mode editing.
|
---|
1805 | The command
|
---|
1806 | .Ql set -o vi
|
---|
1807 | enables vi-mode editing and places sh into vi insert mode.
|
---|
1808 | (See the
|
---|
1809 | .Sx Argument List Processing
|
---|
1810 | section above.)
|
---|
1811 | .Pp
|
---|
1812 | The vi mode uses commands similar to a subset of those described in the
|
---|
1813 | .Xr vi 1
|
---|
1814 | man page.
|
---|
1815 | With vi-mode
|
---|
1816 | enabled, sh can be switched between insert mode and command mode.
|
---|
1817 | It's similar to vi: typing
|
---|
1818 | .Aq ESC
|
---|
1819 | will throw you into command VI command mode.
|
---|
1820 | Hitting
|
---|
1821 | .Aq return
|
---|
1822 | while in command mode will pass the line to the shell.
|
---|
1823 | .Pp
|
---|
1824 | The emacs mode uses commands similar to a subset available in
|
---|
1825 | the emacs editor.
|
---|
1826 | With emacs-mode enabled, special keys can be used to modify the text
|
---|
1827 | in the buffer using the control key.
|
---|
1828 | .Pp
|
---|
1829 | .Nm
|
---|
1830 | uses the
|
---|
1831 | .Xr editline 3
|
---|
1832 | library.
|
---|
1833 | .Sh EXIT STATUS
|
---|
1834 | Errors that are detected by the shell, such as a syntax error, will cause the
|
---|
1835 | shell to exit with a non-zero exit status.
|
---|
1836 | If the shell is not an
|
---|
1837 | interactive shell, the execution of the shell file will be aborted.
|
---|
1838 | Otherwise
|
---|
1839 | the shell will return the exit status of the last command executed, or
|
---|
1840 | if the exit builtin is used with a numeric argument, it will return the
|
---|
1841 | argument.
|
---|
1842 | .Sh ENVIRONMENT
|
---|
1843 | .Bl -tag -width MAILCHECK
|
---|
1844 | .It Ev HOME
|
---|
1845 | Set automatically by
|
---|
1846 | .Xr login 1
|
---|
1847 | from the user's login directory in the password file
|
---|
1848 | .Pq Xr passwd 5 .
|
---|
1849 | This environment variable also functions as the default argument for the
|
---|
1850 | cd builtin.
|
---|
1851 | .It Ev PATH
|
---|
1852 | The default search path for executables.
|
---|
1853 | See the above section
|
---|
1854 | .Sx Path Search .
|
---|
1855 | .It Ev CDPATH
|
---|
1856 | The search path used with the cd builtin.
|
---|
1857 | .It Ev LANG
|
---|
1858 | The string used to specify localization information that allows users
|
---|
1859 | to work with different culture-specific and language conventions.
|
---|
1860 | See
|
---|
1861 | .Xr nls 7 .
|
---|
1862 | .It Ev MAIL
|
---|
1863 | The name of a mail file, that will be checked for the arrival of new mail.
|
---|
1864 | Overridden by
|
---|
1865 | .Ev MAILPATH .
|
---|
1866 | .It Ev MAILCHECK
|
---|
1867 | The frequency in seconds that the shell checks for the arrival of mail
|
---|
1868 | in the files specified by the
|
---|
1869 | .Ev MAILPATH
|
---|
1870 | or the
|
---|
1871 | .Ev MAIL
|
---|
1872 | file.
|
---|
1873 | If set to 0, the check will occur at each prompt.
|
---|
1874 | .It Ev MAILPATH
|
---|
1875 | A colon
|
---|
1876 | .Dq \&:
|
---|
1877 | separated list of file names, for the shell to check for incoming mail.
|
---|
1878 | This environment setting overrides the
|
---|
1879 | .Ev MAIL
|
---|
1880 | setting.
|
---|
1881 | There is a maximum of 10 mailboxes that can be monitored at once.
|
---|
1882 | .It Ev PS1
|
---|
1883 | The primary prompt string, which defaults to
|
---|
1884 | .Dq $ \ ,
|
---|
1885 | unless you are the superuser, in which case it defaults to
|
---|
1886 | .Dq # \ .
|
---|
1887 | .It Ev PS2
|
---|
1888 | The secondary prompt string, which defaults to
|
---|
1889 | .Dq \*[Gt] \ .
|
---|
1890 | .It Ev PS4
|
---|
1891 | Output before each line when execution trace (set -x) is enabled,
|
---|
1892 | defaults to
|
---|
1893 | .Dq + \ .
|
---|
1894 | .It Ev IFS
|
---|
1895 | Input Field Separators.
|
---|
1896 | This is normally set to
|
---|
1897 | .Aq space ,
|
---|
1898 | .Aq tab ,
|
---|
1899 | and
|
---|
1900 | .Aq newline .
|
---|
1901 | See the
|
---|
1902 | .Sx White Space Splitting
|
---|
1903 | section for more details.
|
---|
1904 | .It Ev TERM
|
---|
1905 | The default terminal setting for the shell.
|
---|
1906 | This is inherited by
|
---|
1907 | children of the shell, and is used in the history editing modes.
|
---|
1908 | .It Ev HISTSIZE
|
---|
1909 | The number of lines in the history buffer for the shell.
|
---|
1910 | .El
|
---|
1911 | .Sh FILES
|
---|
1912 | .Bl -item -width HOMEprofilexxxx
|
---|
1913 | .It
|
---|
1914 | .Pa $HOME/.profile
|
---|
1915 | .It
|
---|
1916 | .Pa /etc/profile
|
---|
1917 | .El
|
---|
1918 | .Sh SEE ALSO
|
---|
1919 | .Xr csh 1 ,
|
---|
1920 | .Xr echo 1 ,
|
---|
1921 | .Xr getopt 1 ,
|
---|
1922 | .Xr ksh 1 ,
|
---|
1923 | .Xr login 1 ,
|
---|
1924 | .Xr printf 1 ,
|
---|
1925 | .Xr test 1 ,
|
---|
1926 | .Xr editline 3 ,
|
---|
1927 | .Xr getopt 3 ,
|
---|
1928 | .\" .Xr profile 4 ,
|
---|
1929 | .Xr editrc 5 ,
|
---|
1930 | .Xr passwd 5 ,
|
---|
1931 | .Xr environ 7 ,
|
---|
1932 | .Xr nls 7 ,
|
---|
1933 | .Xr sysctl 8
|
---|
1934 | .Sh HISTORY
|
---|
1935 | A
|
---|
1936 | .Nm
|
---|
1937 | command appeared in
|
---|
1938 | .At v1 .
|
---|
1939 | It was, however, unmaintainable so we wrote this one.
|
---|
1940 | .Sh BUGS
|
---|
1941 | Setuid shell scripts should be avoided at all costs, as they are a
|
---|
1942 | significant security risk.
|
---|
1943 | .Pp
|
---|
1944 | PS1, PS2, and PS4 should be subject to parameter expansion before
|
---|
1945 | being displayed.
|
---|
1946 | .Pp
|
---|
1947 | The characters generated by filename completion should probably be quoted
|
---|
1948 | to ensure that the filename is still valid after the input line has been
|
---|
1949 | processed.
|
---|