1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
2 .\" and Copyright (C) 2007, 2012 Michael Kerrisk <mtk.manpages@gmail.com>
4 .\" Permission is granted to make and distribute verbatim copies of this
5 .\" manual provided the copyright notice and this permission notice are
6 .\" preserved on all copies.
8 .\" Permission is granted to copy and distribute modified versions of this
9 .\" manual under the conditions for verbatim copying, provided that the
10 .\" entire resulting derived work is distributed under the terms of a
11 .\" permission notice identical to this one.
13 .\" Since the Linux kernel and libraries are constantly changing, this
14 .\" manual page may be incorrect or out-of-date. The author(s) assume no
15 .\" responsibility for errors or omissions, or for damages resulting from
16 .\" the use of the information contained herein. The author(s) may not
17 .\" have taken the same level of care in the production of this manual,
18 .\" which is licensed free of charge, as they might when working
21 .\" Formatted or processed versions of this manual, if unaccompanied by
22 .\" the source, must acknowledge the copyright and authors of this work.
24 .\" References consulted:
25 .\" Linux libc source code
26 .\" Lewine's "POSIX Programmer's Guide" (O'Reilly & Associates, 1991)
28 .\" Modified Sat Jul 24 19:30:29 1993 by Rik Faith (faith@cs.unc.edu)
29 .\" Modified Fri Feb 14 21:47:50 1997 by Andries Brouwer (aeb@cwi.nl)
31 .TH GETENV 3 2012-08-14 "GNU" "Linux Programmer's Manual"
33 getenv, secure_getenv \- get an environment variable
36 .B #include <stdlib.h>
38 .BI "char *getenv(const char *" name );
40 .BI "char *secure_getenv(const char *" name );
44 Feature Test Macro Requirements for glibc (see
45 .BR feature_test_macros (7)):
53 function searches the environment list to find the
56 and returns a pointer to the corresponding
64 except that it returns NULL in cases where "secure execution" is required.
65 Secure execution is required if one of the following conditions
66 was true when the program run by the calling process was loaded:
68 the process's effective user ID did not match its real user ID or
69 the process's effective group ID did not match its real group ID
70 (typically this is the result of executing a set-user-ID or
71 set-group-ID program);
73 the effective capability bit was set on the executable file; or
75 the process has a nonempty permitted capability set.
77 Secure execution may also required if triggered
78 by some Linux security modules.
82 function is intended for use in general-purpose libraries
83 to avoid vulnerabilities that could occur if
84 set-user-ID or set-group-ID programs accidentally
85 trusted the environment.
89 function returns a pointer to the value in the
90 environment, or NULL if there is no match.
94 first appeared in glibc 2.17.
98 SVr4, POSIX.1-2001, 4.3BSD, C89, C99.
104 The strings in the environment list are of the form \fIname=value\fP.
106 As typically implemented,
108 returns a pointer to a string within the environment list.
109 The caller must take care not to modify this string,
110 since that would change the environment of the process.
112 The implementation of
114 is not required to be reentrant.
115 The string pointed to by the return value of
117 may be statically allocated,
118 and can be modified by a subsequent call to
125 The "secure execution" mode of
129 flag contained in the auxiliary vector passed from the kernel to user space.
136 .BR capabilities (7),