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@(#)environ.7 8.3 (Berkeley) 4/19/94
.Dd April 19, 1994 .Dt ENVIRON 7 .Os BSD 4.2 .Sh NAME .Nm environ .Nd user environment .Sh SYNOPSIS .Ar extern char **environ ; .Sh DESCRIPTION An array of strings called the .Ar environment is made available by .Xr execve 2 when a process begins. By convention these strings have the form .Dq Ar name=value . The following names are used by various commands: l -tag -width BLOCKSIZE t Ev BLOCKSIZE The size of the block units used by several commands, most notably .Xr df 1 , .Xr du 1 and .Xr ls 1 . BLOCKSIZE may be specified in units of a byte by specifying a number, in units of a kilobyte by specifying a number followed by ``K'' or ``k'', in units of a megabyte by specifying a number followed by ``M'' or ``m'' and in units of a gigabyte by specifying a number followed by ``G'' or ``g''. Sizes less than 512 bytes or greater than a gigabyte are ignored. t Ev EXINIT A startup list of commands read by .Xr ex 1 and .Xr vi 1 . t Ev HOME A user's login directory, set by .Xr login 1 from the password file .Xr passwd 5 . t Ev PATH The sequence of directories, separated by colons, searched by .Xr csh 1 , .Xr sh 1 , .Xr system 3 , .Xr execvp 3 , etc, when looking for an executable file. PATH is set to ``/usr/bin:/bin'' initially by .Xr login 1 . t Ev PRINTER The name of the default printer to be used by .Xr lpr 1 , .Xr lpq 1 , and .Xr lprm 1 . t Ev SHELL The full pathname of the user's login shell. t Ev TERM The kind of terminal for which output is to be prepared. This information is used by commands, such as .Xr nroff 1 which may exploit special terminal capabilities. See .Xr termcap 3 and .Xr terminfo 5 . t Ev TMPDIR The directory in which to store temporary files. Most applications use either .Dq /tmp or .Dq /var/tmp . Setting this variable will make them use another directory. t Ev TZ The timezone to use when displaying dates. The normal format is a pathname relative to .Dq /usr/share/zoneinfo . For example, the command .Dq env TZ=US/Pacific date displays the current time in California. See .Xr tzset 3 for more information. t Ev LOGNAME The login name of the user. t Ev USER Deprecated synonym of .Ev LOGNAME (for backwards compatibility). .El
p Further names may be placed in the environment by the .Xr export command and .Ar name=value arguments in .Xr sh 1 , or by the .Xr setenv command if you use .Xr csh 1 . It is unwise to change certain .Xr sh 1 variables that are frequently exported by
a .profile files, such as .Ev MAIL , .Ev PS1 , .Ev PS2 , and .Ev IFS , unless you know what you are doing. .Sh PROGRAMMING Programs can query and modify the environment, using the environment routines .Xr getenv 3 , .Xr putenv 3 , .Xr setenv 3 and .Xr unsetenv 3 . Direct access can be made through the global variable .Va environ , though it is recommended that changes to the enviroment still be made through the environment routines.
p Shared libraries and bundles don't have direct access to .Va environ , which is only available to the loader .Xr ld 1 when a complete program is being linked. The environment routines can still be used, but if direct access to .Va environ is needed, the .Fn _NSGetEnviron routine, defined in n crt_externs.h , can be used to retrieve the address of .Va environ at runtime. .Sh SEE ALSO .Xr csh 1 , .Xr ex 1 , .Xr login 1 , .Xr sh 1 , .Xr getenv 3 , .Xr putenv 3 , .Xr setenv 3 , .Xr unsetenv 3 , .Xr execve 2 , .Xr execle 3 , .Xr system 3 , .Xr termcap 3 , .Xr terminfo 5 .Sh HISTORY The .Nm environ manual page appeared in x 4.2 .