man/environ.7

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  34 .\"     @(#)environ.7   8.3 (Berkeley) 4/19/94
  35 .\"
  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 .Xr edit  1 ,
  69 and
  70 .Xr vi  1  .
  71 .It Ev HOME
  72 A user's login directory, set by
  73 .Xr login  1
  74 from the password file
  75 .Xr passwd  5  .
  76 .It Ev PATH
  77 The sequence of directories, separated by colons, searched by
  78 .Xr csh  1  ,
  79 .Xr sh  1 ,
  80 .Xr system  3  ,
  81 .Xr execvp  3 ,
  82 etc, when looking for an executable file.
  83 PATH is set to ``/usr/bin:/bin'' initially by
  84 .Xr login  1  .
  85 .It Ev PRINTER
  86 The name of the default printer to be used by
  87 .Xr lpr  1  ,
  88 .Xr lpq  1 ,
  89 and
  90 .Xr lprm  1  .
  91 .It Ev SHELL
  92 The full pathname of the user's login shell.
  93 .It Ev TERM
  94 The kind of terminal for which output is to be prepared.
  95 This information is used by commands, such as
  96 .Xr nroff  1
  97 or
  98 .Xr plot 1
  99 which may exploit special terminal capabilities.  See
 100 .Pa /usr/share/misc/termcap
 101 .Pq Xr termcap 5
 102 for a list of terminal types.
 103 .It Ev TERMCAP
 104 The string describing the terminal in TERM, or, if
 105 it begins with a '/', the name of the termcap file.
 106 See
 107 .Ev TERMPATH
 108 below,
 109 .Xr termcap  5  ,
 110 and
 111 .Xr termcap  .
 112 .It Ev TERMPATH
 113 A sequence of pathnames of termcap files, separated by colons or spaces,
 114 which are searched for terminal descriptions in the order listed.  Having
 115 no
 116 .Ev TERMPATH
 117 is equivalent to a
 118 .Ev TERMPATH
 119 of
 120 .Dq Pa $HOME/.termcap:/etc/termcap .
 121 .Ev TERMPATH
 122 is ignored if
 123 .Ev TERMCAP
 124 contains a full pathname.
 125 .It Ev TMPDIR
 126 The directory in which to store temporary files.
 127 Most applications use either
 128 .Dq /tmp
 129 or
 130 .Dq /var/tmp .
 131 Setting this variable will make them use another directory.
 132 .It Ev TZ
 133 The timezone to use when displaying dates.
 134 The normal format is a pathname relative to
 135 .Dq /usr/share/zoneinfo .
 136 For example, the command
 137 .Dq env TZ=US/Pacific date
 138 displays the current time in California.
 139 See
 140 .Xr tzset 3
 141 for more information.
 142 .It Ev LOGNAME
 143 The login name of the user.
 144 .It Ev USER
 145 Deprecated synonym of
 146 .Ev LOGNAME
 147 (for backwards compatibility).
 148 .El
 149 .Pp
 150 Further names may be placed in the environment by the
 151 .Xr export
 152 command and
 153 .Ar name=value
 154 arguments in
 155 .Xr sh  1  ,
 156 or by the
 157 .Xr setenv
 158 command if you use
 159 .Xr csh  1  .
 160 It is unwise to change certain
 161 .Xr sh  1
 162 variables that are frequently exported by
 163 .Pa .profile
 164 files, such as
 165 .Ev MAIL ,
 166 .Ev PS1 ,
 167 .Ev PS2 ,
 168 and
 169 .Ev IFS ,
 170 unless you know what you are doing.
 171 .Sh PROGRAMMING
 172 Programs can query and modify the environment, using the environment routines
 173 .Xr getenv 3 ,
 174 .Xr putenv 3 ,
 175 .Xr setenv 3
 176 and
 177 .Xr unsetenv 3 .
 178 Direct access can be made through the global variable
 179 .Va environ ,
 180 though it is recommended that changes to the enviroment still be made through
 181 the environment routines.
 182 .Pp
 183 Shared libraries and bundles don't have direct access to
 184 .Va environ ,
 185 which is only available to the loader
 186 .Xr ld 1
 187 when a complete program is being linked.
 188 The environment routines can still be used, but if direct access to
 189 .Va environ
 190 is needed, the
 191 .Fn _NSGetEnviron
 192 routine, defined in
 193 .In crt_externs.h ,
 194 can be used to retrieve the address of
 195 .Va environ
 196 at runtime.
 197 .Sh SEE ALSO
 198 .Xr csh 1 ,
 199 .Xr ex 1 ,
 200 .Xr login 1 ,
 201 .Xr sh 1 ,
 202 .Xr getenv 3 ,
 203 .Xr putenv 3 ,
 204 .Xr setenv 3 ,
 205 .Xr unsetenv 3 ,
 206 .Xr execve 2 ,
 207 .Xr execle 3 ,
 208 .Xr system 3 ,
 209 .Xr termcap 3 ,
 210 .Xr termcap 5
 211 .Sh HISTORY
 212 The
 213 .Nm environ
 214 manual page appeared in
 215 .Bx 4.2 .