setenv(3) - Linux manual page (original) (raw)

setenv(3) Library Functions Manual setenv(3)

NAME top

   setenv - change or add an environment variable

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#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 top

   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)](../man3/putenv.3.html)).

   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 top

   **setenv**() and **unsetenv**() functions return zero on success, or -1 on
   error, with _[errno](../man3/errno.3.html)_ set to indicate the error.

ERRORS top

   **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 top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌──────────────────────────┬───────────────┬─────────────────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────┼───────────────┼─────────────────────┤
   │ **setenv**(), **unsetenv**()     │ Thread safety │ MT-Unsafe const:env │
   └──────────────────────────┴───────────────┴─────────────────────┘

STANDARDS top

   POSIX.1-2008.

HISTORY top

   POSIX.1-2001, 4.3BSD.

   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.

CAVEATS top

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

BUGS top

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

COLOPHON top

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Linux man-pages 6.10 2024-07-23 setenv(3)

setenv(3) - Linux manual page (original) (raw)

NAME top

LIBRARY top

SYNOPSIS top

DESCRIPTION top

RETURN VALUE top

ERRORS top

ATTRIBUTES top

STANDARDS top

HISTORY top

CAVEATS top

BUGS top

SEE ALSO top

COLOPHON top