Section (3) getenv
getenv, secure_getenv — get an environment variable
||const char *name
||const char *name
searches the environment list to find the environment
returns a pointer to the corresponding
secure_getenv() function is just like
getenv() except that it returns
NULL in cases where secure execution is required. Secure
execution is required if one of the following conditions was
true when the program run by the calling process was
the process_zsingle_quotesz_s effective user ID did not match its real user ID or the process_zsingle_quotesz_s effective group ID did not match its real group ID (typically this is the result of executing a set-user-ID or set-group-ID program);
the effective capability bit was set on the executable file; or
the process has a nonempty permitted capability set.
Secure execution may also be required if triggered by some Linux security modules.
is intended for use in general-purpose libraries to avoid
vulnerabilities that could occur if set-user-ID or
set-group-ID programs accidentally trusted the
returns a pointer to the value in the environment, or NULL if
there is no match.
For an explanation of the terms used in this section, see attributes(7).
||Thread safety||MT-Safe env|
POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
secure_getenv() is a GNU
The strings in the environment list are of the form
As typically implemented,
getenv() returns a pointer to a string
within the environment list. The caller must take care not to
modify this string, since that would change the environment
of the process.
The implementation of
getenv() is not required to be reentrant.
The string pointed to by the return value of
getenv() may be statically allocated, and
can be modified by a subsequent call to
getenv(), putenv(3), setenv(3), or unsetenv(3).
The secure execution mode of
secure_getenv() is controlled by the
AT_SECURE flag contained in the
auxiliary vector passed from the kernel to user space.
This page is part of release 4.16 of the Linux
man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
Copyright 1993 David Metcalfe (davidprism.demon.co.uk)
and Copyright (C) 2007, 2012 Michael Kerrisk <mtk.manpagesgmail.com>
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.
Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date. The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein. The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working
Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.
Linux libc source code
Lewine_zsingle_quotesz_s POSIX Programmer_zsingle_quotesz_s Guide (O_zsingle_quotesz_Reilly & Associates, 1991)
386BSD man pages
Modified Sat Jul 24 19:30:29 1993 by Rik Faith (faithcs.unc.edu)
Modified Fri Feb 14 21:47:50 1997 by Andries Brouwer (aebcwi.nl)