| 1 | .\" Copyright (c) 1983 Regents of the University of California.
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| 2 | .\" All rights reserved. The Berkeley software License Agreement
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| 3 | .\" specifies the terms and conditions for redistribution.
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| 4 | .\"
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| 5 | .\" @(#)environ.7 6.1 (Berkeley) 5/20/85
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| 6 | .\"
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| 7 | .TH ENVIRON 7 "May 20, 1985"
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| 8 | .UC 5
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| 9 | .SH NAME
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| 10 | environ \- user environment
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| 11 | .SH SYNOPSIS
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| 12 | .B "extern char *const *environ;"
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| 13 | .SH DESCRIPTION
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| 14 | An array of strings called the `environment' is made available by
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| 15 | .BR execve (2)
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| 16 | when a process begins. By convention these strings have the form
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| 17 | .RI ` name = value '.
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| 18 | The following names are used by various commands:
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| 19 | .TP "\w'TERMCAP 'u"
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| 20 | .B PATH
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| 21 | The sequence of directory prefixes that
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| 22 | .BR sh ,
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| 23 | .BR time ,
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| 24 | .BR nice (1),
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| 25 | etc., apply in searching for a file known by an incomplete path name.
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| 26 | The prefixes are separated by `:'.
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| 27 | Login shells set
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| 28 | .BR PATH=:/bin:/usr/bin .
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| 29 | Note that the empty space between the `=' and the `:' indicates the current
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| 30 | directory. Security aware people move the extra `:' to the end of their
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| 31 | path or omit it.
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| 32 | .TP
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| 33 | .B HOME
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| 34 | A user's login directory, set by
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| 35 | .BR login (1)
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| 36 | from the password file
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| 37 | .BR passwd (5).
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| 38 | .TP
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| 39 | .B TERM
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| 40 | The kind of terminal for which output is to be prepared.
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| 41 | This information is used by programs that wish to exploit special
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| 42 | terminal capabilities, a screen oriented text editor for instance.
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| 43 | The terminal type is set by
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| 44 | .BR login (1)
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| 45 | from the tty database
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| 46 | .BR ttytab (5).
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| 47 | .TP
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| 48 | .B SHELL
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| 49 | The file name of the users login shell, set by
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| 50 | .BR login (1)
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| 51 | from the password file
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| 52 | .BR passwd (5).
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| 53 | .TP
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| 54 | .B TERMCAP
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| 55 | The string describing the terminal in TERM, or the name of the termcap file,
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| 56 | see
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| 57 | .BR termcap (5),
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| 58 | .BR termcap (3).
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| 59 | .TP
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| 60 | .B EXINIT
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| 61 | A startup list of commands read by
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| 62 | .BR elvis (1).
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| 63 | .TP
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| 64 | .B USER
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| 65 | The login name of the user, set by
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| 66 | .BR login (1)
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| 67 | from the password file
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| 68 | .BR passwd (5).
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| 69 | .TP
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| 70 | .B LOGNAME
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| 71 | Set to the same value as
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| 72 | .BR USER .
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| 73 | BSD derived systems have
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| 74 | .BR USER ,
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| 75 | System V has
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| 76 | .BR LOGNAME ,
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| 77 | so modern systems have both to avoid problems.
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| 78 | .TP
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| 79 | .PP
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| 80 | Further names may be placed in the environment by the
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| 81 | .B export
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| 82 | command and
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| 83 | .RI ` name = value '
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| 84 | arguments in
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| 85 | .BR sh (1).
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| 86 | Arguments may also be placed in their environment by
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| 87 | programs if they use
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| 88 | .BR putenv (3).
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| 89 | Or in the environment of another program by building a new environment
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| 90 | for one of the exec functions that accepts an environment list, like
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| 91 | .BR execle (2)
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| 92 | or
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| 93 | .BR execve (2).
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| 94 | It is unwise to conflict with certain
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| 95 | .BR sh (1)
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| 96 | variables that are frequently set and/or exported by `.profile' files:
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| 97 | .BR MAIL ,
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| 98 | .BR PS1 ,
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| 99 | .BR PS2 ,
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| 100 | .BR IFS .
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| 101 | .SH SEE ALSO
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| 102 | .BR elvis (1),
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| 103 | .BR login (1),
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| 104 | .BR sh (1),
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| 105 | .BR execl (3),
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| 106 | .BR execve (2),
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| 107 | .BR system (3),
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| 108 | .BR termcap (3),
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| 109 | .BR termcap (5),
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| 110 | .BR passwd (5),
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| 111 | .BR ttytab (5).
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