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

       setenv - change or add an environment variable

       #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():
	   _BSD_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600

       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.

       The setenv() function returns zero on success, or -1 on error, with errno set to  indicate
       the cause of the error.

       The  unsetenv()	function returns zero on success, or -1 on error, with errno set to indi-
       cate the cause of the error.

       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.

       4.3BSD, POSIX.1-2001.

       POSIX.1-2001 does not require setenv() or unsetenv() to be reentrant.

       Prior to glibc 2.2.2, unsetenv() was prototyped as returning void; more recent glibc  ver-
       sions follow the POSIX.1-2001-compliant prototype shown in the SYNOPSIS.

       POSIX.1-2001  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

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

       This  page  is  part of release 3.55 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at

GNU					    2013-10-11					SETENV(3)
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