mirror of https://github.com/mkerrisk/man-pages
127 lines
3.7 KiB
Groff
127 lines
3.7 KiB
Groff
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\" and Copyright (C) 2004, 2007 Michael kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Modified Sat Jul 24 18:20:58 1993 by Rik Faith (faith@cs.unc.edu)
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.\" Modified Fri Feb 14 21:47:50 1997 by Andries Brouwer (aeb@cwi.nl)
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.\" Modified 9 Jun 2004, Michael Kerrisk <mtk.manpages@gmail.com>
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.\" Changed unsetenv() prototype; added EINVAL error
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.\" Noted non-standard behavior of setenv() if name contains '='
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.\" 2005-08-12, mtk, glibc 2.3.4 fixed the "name contains '='" bug
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.\"
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.TH SETENV 3 2007-07-26 "GNU" "Linux Programmer's Manual"
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.SH NAME
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setenv \- change or add an environment variable
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.SH SYNOPSIS
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.nf
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.B #include <stdlib.h>
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.sp
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.BI "int setenv(const char *" name ", const char *" value ", int " overwrite );
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.sp
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.BI "int unsetenv(const char *" name );
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.fi
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.ad l
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.BR setenv (),
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.BR unsetenv ():
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_BSD_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE\ >=\ 600
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.ad b
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.SH DESCRIPTION
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The
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.BR setenv ()
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function adds the variable \fIname\fP to the
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environment with the value \fIvalue\fP, if \fIname\fP does not
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already exist.
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If \fIname\fP does exist in the environment, then
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its value is changed to \fIvalue\fP if \fIoverwrite\fP is non-zero;
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if \fIoverwrite\fP is zero, then the value of \fIname\fP is not
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changed.
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This function makes copies of the strings pointed to by
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.I name
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and
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.I value
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(by contrast with
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.BR putenv (3)).
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.PP
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The
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.BR unsetenv ()
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function deletes the variable \fIname\fP from
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the environment.
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If
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.I name
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does not exist in the environment,
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then the function succeeds, and the environment is unchanged.
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.SH "RETURN VALUE"
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The
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.BR setenv ()
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function returns zero on success, or \-1 if there
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was insufficient space in the environment.
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The
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.BR unsetenv ()
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function returns zero on success,
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or \-1 on error, with
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.I errno
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set to indicate the cause of the error.
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.SH "ERRORS"
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.TP
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.B EINVAL
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.I name
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contained an \(aq=\(aq character.
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.SH "CONFORMING TO"
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4.3BSD, POSIX.1-2001.
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.SH "NOTES"
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POSIX.1-2001 does not require
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.BR setenv ()
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or
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.BR unsetenv ()
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to be reentrant.
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Prior to glibc 2.2.2,
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.BR unsetenv ()
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was prototyped
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as returning \fIvoid\fP; more recent glibc versions follow the
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POSIX.1-2001-compliant prototype shown in the SYNOPSIS.
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.SH BUGS
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POSIX.1-2001 specifies that if
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.I name
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contains an \(aq=\(aq character, then
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.BR setenv ()
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should fail with the error
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.BR EINVAL ;
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however, versions of glibc before 2.3.4 allowed an \(aq=\(aq sign in
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.IR name .
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.SH "SEE ALSO"
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.BR clearenv (3),
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.BR getenv (3),
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.BR putenv (3),
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.BR environ (7)
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