getenv

       #include <stdlib.h>

       char *getenv(const char *name);

       char *secure_getenv(const char *name);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       secure_getenv(): _GNU_SOURCE

DESCRIPTION
       The  getenv()  function searches the environment list to find the envi-
       ronment variable name, and returns a pointer to the corresponding value
       string.

       The  GNU-specific 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 loaded:

       *  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);

       *  the effective capability bit was set on the executable file; or

       *  the process has a nonempty permitted capability set.

       Secure  execution may also required if triggered by some Linux security
       modules.

       The 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.

RETURN VALUE
       The getenv() function returns a pointer to the value  in  the  environ-
       ment, or NULL if there is no match.

VERSIONS
       secure_getenv() first appeared in glibc 2.17.

ATTRIBUTES
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).

       +--------------------------+---------------+-------------+
       |Interface                 | Attribute     | Value       |
       +--------------------------+---------------+-------------+
       |getenv(), secure_getenv() | Thread safety | MT-Safe env |
       +--------------------------+---------------+-------------+
CONFORMING TO
       getenv(): POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
       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.

SEE ALSO
       clearenv(3), getauxval(3), putenv(3), setenv(3), unsetenv(3), capabili-
       ties(7), environ(7)

COLOPHON
       This page is part of release 4.04 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
       http://www.kernel.org/doc/man-pages/.

GNU                               2015-08-08                         GETENV(3)
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