getenv (3) - Linux Man Pages
getenv: get an environment variable
NAMEgetenv, secure_getenv - get an environment variable
#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)):
DESCRIPTIONThe getenv() function searches the environment list to find the environment 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 be required if triggered by some Linux security modules.
RETURN VALUEThe getenv() function returns a pointer to the value in the environment, or NULL if there is no match.
VERSIONSsecure_getenv() first appeared in glibc 2.17.
ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7).
|getenv(), secure_getenv()||Thread safety||MT-Safe env|
CONFORMING TOgetenv(): POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
NOTESThe strings in the environment list are of the form name=value.
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).
SEE ALSOclearenv(3), getauxval(3), putenv(3), setenv(3), unsetenv(3), capabilities(7), environ(7)
COLOPHONThis page is part of release 4.15 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 https://www.kernel.org/doc/man-pages/.
Linux man pages generated by: SysTutorials