112 lines
2.6 KiB
Groff
112 lines
2.6 KiB
Groff
.\" Copyright (c) 1983 Regents of the University of California.
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.\" All rights reserved. The Berkeley software License Agreement
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.\" specifies the terms and conditions for redistribution.
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.\"
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.\" @(#)environ.7 6.1 (Berkeley) 5/20/85
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.\"
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.TH ENVIRON 7 "May 20, 1985"
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.UC 5
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.SH NAME
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environ \- user environment
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.SH SYNOPSIS
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.B "extern char *const *environ;"
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.SH DESCRIPTION
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An array of strings called the `environment' is made available by
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.BR execve (2)
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when a process begins. By convention these strings have the form
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.RI ` name = value '.
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The following names are used by various commands:
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.TP "\w'TERMCAP 'u"
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.B PATH
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The sequence of directory prefixes that
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.BR sh ,
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.BR time ,
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.BR nice (1),
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etc., apply in searching for a file known by an incomplete path name.
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The prefixes are separated by `:'.
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Login shells set
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.BR PATH=:/bin:/usr/bin .
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Note that the empty space between the `=' and the `:' indicates the current
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directory. Security aware people move the extra `:' to the end of their
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path or omit it.
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.TP
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.B HOME
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A user's login directory, set by
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.BR login (1)
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from the password file
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.BR passwd (5).
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.TP
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.B TERM
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The kind of terminal for which output is to be prepared.
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This information is used by programs that wish to exploit special
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terminal capabilities, a screen oriented text editor for instance.
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The terminal type is set by
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.BR login (1)
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from the tty database
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.BR ttytab (5).
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.TP
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.B SHELL
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The file name of the users login shell, set by
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.BR login (1)
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from the password file
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.BR passwd (5).
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.TP
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.B TERMCAP
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The string describing the terminal in TERM, or the name of the termcap file,
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see
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.BR termcap (5),
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.BR termcap (3).
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.TP
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.B EXINIT
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A startup list of commands read by
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.BR elvis (1).
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.TP
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.B USER
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The login name of the user, set by
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.BR login (1)
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from the password file
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.BR passwd (5).
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.TP
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.B LOGNAME
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Set to the same value as
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.BR USER .
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BSD derived systems have
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.BR USER ,
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System V has
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.BR LOGNAME ,
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so modern systems have both to avoid problems.
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.TP
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.PP
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Further names may be placed in the environment by the
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.B export
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command and
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.RI ` name = value '
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arguments in
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.BR sh (1).
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Arguments may also be placed in their environment by
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programs if they use
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.BR putenv (3).
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Or in the environment of another program by building a new environment
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for one of the exec functions that accepts an environment list, like
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.BR execle (2)
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or
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.BR execve (2).
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It is unwise to conflict with certain
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.BR sh (1)
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variables that are frequently set and/or exported by `.profile' files:
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.BR MAIL ,
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.BR PS1 ,
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.BR PS2 ,
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.BR IFS .
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.SH SEE ALSO
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.BR elvis (1),
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.BR login (1),
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.BR sh (1),
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.BR execl (3),
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.BR execve (2),
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.BR system (3),
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.BR termcap (3),
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.BR termcap (5),
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.BR passwd (5),
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.BR ttytab (5).
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