man/environ.7

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  34 .\"     @(#)environ.7   8.3 (Berkeley) 4/19/94
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  36 .Dd April 19, 1994
  37 .Dt ENVIRON 7
  38 .Os BSD 4.2
  39 .Sh NAME
  40 .Nm environ
  41 .Nd user environment
  42 .Sh SYNOPSIS
  43 .Ar extern char **environ ;
  44 .Sh DESCRIPTION
  45 An array of strings called the
  46 .Ar environment
  47 is made available by
  48 .Xr execve  2
  49 when a process begins.  By convention these strings have the form
  50 .Dq Ar name=value .
  51 The following names are used by various commands:
  52 .Bl -tag -width BLOCKSIZE
  53 .It Ev BLOCKSIZE
  54 The size of the block units used by several commands, most notably
  55 .Xr df 1 ,
  56 .Xr du 1
  57 and
  58 .Xr ls 1 .
  59 BLOCKSIZE may be specified in units of a byte by specifying a number,
  60 in units of a kilobyte by specifying a number followed by ``K'' or
  61 ``k'', in units of a megabyte by specifying a number followed by ``M''
  62 or ``m'' and in units of a gigabyte by specifying a number followed
  63 by ``G'' or ``g''.
  64 Sizes less than 512 bytes or greater than a gigabyte are ignored.
  65 .It Ev EXINIT
  66 A startup list of commands read by
  67 .Xr ex  1
  68 and
  69 .Xr vi  1  .
  70 .It Ev HOME
  71 A user's login directory, set by
  72 .Xr login  1
  73 from the password file
  74 .Xr passwd  5  .
  75 .It Ev PATH
  76 The sequence of directories, separated by colons, searched by
  77 .Xr csh  1  ,
  78 .Xr sh  1 ,
  79 .Xr system  3  ,
  80 .Xr execvp  3 ,
  81 etc, when looking for an executable file.
  82 PATH is set to ``/usr/bin:/bin'' initially by
  83 .Xr login  1  .
  84 .It Ev PRINTER
  85 The name of the default printer to be used by
  86 .Xr lpr  1  ,
  87 .Xr lpq  1 ,
  88 and
  89 .Xr lprm  1  .
  90 .It Ev SHELL
  91 The full pathname of the user's login shell.
  92 .It Ev TERM
  93 The kind of terminal for which output is to be prepared.
  94 This information is used by commands, such as
  95 .Xr nroff  1
  96 which may exploit special terminal capabilities.  See
  97 .Xr termcap 3
  98 and
  99 .Xr terminfo 5 .
 100 .It Ev TMPDIR
 101 The directory in which to store temporary files.
 102 Most applications use either
 103 .Dq /tmp
 104 or
 105 .Dq /var/tmp .
 106 Setting this variable will make them use another directory.
 107 .It Ev TZ
 108 The timezone to use when displaying dates.
 109 The normal format is a pathname relative to
 110 .Dq /usr/share/zoneinfo .
 111 For example, the command
 112 .Dq env TZ=US/Pacific date
 113 displays the current time in California.
 114 See
 115 .Xr tzset 3
 116 for more information.
 117 .It Ev LOGNAME
 118 The login name of the user.
 119 .It Ev USER
 120 Deprecated synonym of
 121 .Ev LOGNAME
 122 (for backwards compatibility).
 123 .El
 124 .Pp
 125 Further names may be placed in the environment by the
 126 .Xr export
 127 command and
 128 .Ar name=value
 129 arguments in
 130 .Xr sh  1  ,
 131 or by the
 132 .Xr setenv
 133 command if you use
 134 .Xr csh  1  .
 135 It is unwise to change certain
 136 .Xr sh  1
 137 variables that are frequently exported by
 138 .Pa .profile
 139 files, such as
 140 .Ev MAIL ,
 141 .Ev PS1 ,
 142 .Ev PS2 ,
 143 and
 144 .Ev IFS ,
 145 unless you know what you are doing.
 146 .Sh PROGRAMMING
 147 Programs can query and modify the environment, using the environment routines
 148 .Xr getenv 3 ,
 149 .Xr putenv 3 ,
 150 .Xr setenv 3
 151 and
 152 .Xr unsetenv 3 .
 153 Direct access can be made through the global variable
 154 .Va environ ,
 155 though it is recommended that changes to the enviroment still be made through
 156 the environment routines.
 157 .Pp
 158 Shared libraries and bundles don't have direct access to
 159 .Va environ ,
 160 which is only available to the loader
 161 .Xr ld 1
 162 when a complete program is being linked.
 163 The environment routines can still be used, but if direct access to
 164 .Va environ
 165 is needed, the
 166 .Fn _NSGetEnviron
 167 routine, defined in
 168 .In crt_externs.h ,
 169 can be used to retrieve the address of
 170 .Va environ
 171 at runtime.
 172 .Sh SEE ALSO
 173 .Xr csh 1 ,
 174 .Xr ex 1 ,
 175 .Xr login 1 ,
 176 .Xr sh 1 ,
 177 .Xr getenv 3 ,
 178 .Xr putenv 3 ,
 179 .Xr setenv 3 ,
 180 .Xr unsetenv 3 ,
 181 .Xr execve 2 ,
 182 .Xr execle 3 ,
 183 .Xr system 3 ,
 184 .Xr termcap 3 ,
 185 .Xr terminfo 5
 186 .Sh HISTORY
 187 The
 188 .Nm environ
 189 manual page appeared in
 190 .Bx 4.2 .