setenv

SETENV(3)                   Linux Programmer's Manual                  SETENV(3)



NAME
       setenv - change or add an environment variable

SYNOPSIS
       #include <stdlib.h>

       int setenv(const char *name, const char *value, int overwrite);

       int unsetenv(const char *name);

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

       setenv(), unsetenv():
           _POSIX_C_SOURCE >= 200112L
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE

DESCRIPTION
       The setenv() function adds the variable name to the environment with the
       value value, if name does not already exist.  If name does exist in the
       environment, then its value is changed to value if overwrite is nonzero;
       if overwrite is zero, then the value of name is not changed (and setenv()
       returns a success status).  This function makes copies of the strings
       pointed to by name and value (by contrast with putenv(3)).

       The unsetenv() function deletes the variable name from the environment.
       If name does not exist in the environment, then the function succeeds,
       and the environment is unchanged.

RETURN VALUE
       setenv() and unsetenv() functions return zero on success, or -1 on error,
       with errno set to indicate the cause of the error.

ERRORS
       EINVAL name is NULL, points to a string of length 0, or contains an '='
              character.

       ENOMEM Insufficient memory to add a new variable to the environment.

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

       ┌─────────────────────┬───────────────┬─────────────────────┐
       │Interface            Attribute     Value               │
       ├─────────────────────┼───────────────┼─────────────────────┤
       │setenv(), unsetenv() │ Thread safety │ MT-Unsafe const:env │
       └─────────────────────┴───────────────┴─────────────────────┘
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008, 4.3BSD.

NOTES
       POSIX.1 does not require setenv() or unsetenv() to be reentrant.

       Prior to glibc 2.2.2, unsetenv() was prototyped as returning void; more
       recent glibc versions follow the POSIX.1-compliant prototype shown in the
       SYNOPSIS.

BUGS
       POSIX.1 specifies that if name contains an '=' character, then setenv()
       should fail with the error EINVAL; however, versions of glibc before
       2.3.4 allowed an '=' sign in name.

SEE ALSO
       clearenv(3), getenv(3), putenv(3), environ(7)

COLOPHON
       This page is part of release 5.09 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/.



GNU                                2017-09-15                          SETENV(3)