Manpages - setenv.3

Table of Contents

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 <= 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 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 5.13 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/.

Author: dt

Created: 2022-02-20 Sun 18:57