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| author | Alejandro Colomar <alx.manpages@gmail.com> | 2022-09-09 14:15:08 +0200 |
|---|---|---|
| committer | Alejandro Colomar <alx.manpages@gmail.com> | 2022-09-09 14:15:08 +0200 |
| commit | 96e72ec1fbadd13cbcbc2b263540e4f5e9e09d7c (patch) | |
| tree | 70686b943e33a6e939ad265acb7ddfef70b91f32 /man3/getenv.3 | |
| parent | 8f4ed6463206e8ede815c72085c7305dafc2e4fc (diff) | |
| download | man-pages-96e72ec1fbadd13cbcbc2b263540e4f5e9e09d7c.tar.gz | |
Revert "src.mk, All pages: Move man* to man/"
This reverts commit 70ac1c4785fc1e158ab2349a962dba2526bf4fbc.
Link: <https://lore.kernel.org/linux-man/YxcV4h+Xn7cd6+q2@pevik/T/>
Reported-by: Petr Vorel <pvorel@suse.cz>
Reported-by: Jakub Wilk <jwilk@jwilk.net>
Cc: Stefan Puiu <stefan.puiu@gmail.com>
Signed-off-by: Alex Colomar <alx.manpages@gmail.com>
Diffstat (limited to 'man3/getenv.3')
| -rw-r--r-- | man3/getenv.3 | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/man3/getenv.3 b/man3/getenv.3 new file mode 100644 index 0000000000..ba40270789 --- /dev/null +++ b/man3/getenv.3 @@ -0,0 +1,138 @@ +.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) +.\" and Copyright (C) 2007, 2012 Michael Kerrisk <mtk.manpages@gmail.com> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.\" References consulted: +.\" Linux libc source code +.\" Lewine's "POSIX Programmer's Guide" (O'Reilly & Associates, 1991) +.\" 386BSD man pages +.\" Modified Sat Jul 24 19:30:29 1993 by Rik Faith (faith@cs.unc.edu) +.\" Modified Fri Feb 14 21:47:50 1997 by Andries Brouwer (aeb@cwi.nl) +.\" +.TH GETENV 3 2021-03-22 "Linux man-pages (unreleased)" +.SH NAME +getenv, secure_getenv \- get an environment variable +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <stdlib.h> +.PP +.BI "char *getenv(const char *" name ); +.BI "char *secure_getenv(const char *" name ); +.fi +.PP +.RS -4 +Feature Test Macro Requirements for glibc (see +.BR feature_test_macros (7)): +.RE +.PP +.BR secure_getenv (): +.nf + _GNU_SOURCE +.fi +.SH DESCRIPTION +The +.BR getenv () +function searches the environment list to find the +environment variable +.IR name , +and returns a pointer to the corresponding +.I value +string. +.PP +The GNU-specific +.BR secure_getenv () +function is just like +.BR 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 loaded: +.IP * 3 +the process's effective user ID did not match its real user ID or +the process'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); +.IP * +the effective capability bit was set on the executable file; or +.IP * +the process has a nonempty permitted capability set. +.PP +Secure execution may also be required if triggered +by some Linux security modules. +.PP +The +.BR secure_getenv () +function 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 environment. +.SH RETURN VALUE +The +.BR getenv () +function returns a pointer to the value in the +environment, or NULL if there is no match. +.SH VERSIONS +.BR secure_getenv () +first appeared in glibc 2.17. +.SH ATTRIBUTES +For an explanation of the terms used in this section, see +.BR attributes (7). +.ad l +.nh +.TS +allbox; +lbx lb lb +l l l. +Interface Attribute Value +T{ +.BR getenv (), +.BR secure_getenv () +T} Thread safety MT-Safe env +.TE +.hy +.ad +.sp 1 +.SH STANDARDS +.BR getenv (): +POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD. +.PP +.BR secure_getenv () +is a GNU extension. +.SH NOTES +The strings in the environment list are of the form \fIname=value\fP. +.PP +As typically implemented, +.BR 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. +.PP +The implementation of +.BR getenv () +is not required to be reentrant. +The string pointed to by the return value of +.BR getenv () +may be statically allocated, +and can be modified by a subsequent call to +.BR getenv (), +.BR putenv (3), +.BR setenv (3), +or +.BR unsetenv (3). +.PP +The "secure execution" mode of +.BR secure_getenv () +is controlled by the +.B AT_SECURE +flag contained in the auxiliary vector passed from the kernel to user space. +.SH SEE ALSO +.BR clearenv (3), +.BR getauxval (3), +.BR putenv (3), +.BR setenv (3), +.BR unsetenv (3), +.BR capabilities (7), +.BR environ (7) |