environ(5)
NAME
environ − user environment
DESCRIPTION
An array of strings called the “environment” is made available by the exec system call when a process begins. By convention, these strings have the form “name=value”. The following names are used by various commands:
PATH The sequence of directory prefixes that sh(1), time(1), nice(1), and so on, apply in searching for a file known by an incomplete path name. The prefixes are separated by colons (:). The login command sets PATH=:/bin:/usr/bin.
HOME Name of the user’s login directory, set by login(1). For further information, see passwd(5).
TERM The kind of terminal for which output is to be prepared. This information is used by commands, such as mm(1), which may exploit special capabilities of that terminal.
TZ Time zone information. The format is xxxnzzz where xxx is standard local time zone abbreviation, n is the difference in hours from GMT, and zzz is the abbreviation for the daylight-saving local time zone, if any; for example, EST5EDT.
Further names may be placed in the environment by the export command and “name=value” arguments in sh(1), or by exec(2). It is unwise to conflict with certain shell variables that are frequently exported by .profile files: MAIL, PS1, PS2, IFS.