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    Command:

    unsetenv

    
    
    

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

    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

           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 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.
    
    
    

    CONFORMING TO

           4.3BSD, POSIX.1-2001.
    
    
    

    NOTES

           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 versions follow the POSIX.1-2001-compliant prototype shown
           in the SYNOPSIS.
    
    
    

    BUGS

           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 name.
    
    
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