getenv(3) - NetBSD Manual Pages

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GETENV(3)                 NetBSD Programmer's Manual                 GETENV(3)


NAME

     getenv, putenv, setenv, unsetenv - environment variable functions


SYNOPSIS

     #include <stdlib.h>

     char *
     getenv(const char *name);

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

     int
     putenv(const char *string);

     void
     unsetenv(const char *name);


DESCRIPTION

     These functions set, unset and fetch environment variables from the host
     environment list. For compatibility with differing environment conven-
     tions, the given arguments name and value may be appended and prepended,
     respectively, with an equal sign ``=''.

     The getenv() function obtains the current value of the environment vari-
     able, name. If the variable name is not in the current environment , a
     null pointer is returned.

     The setenv() function inserts or resets the environment variable name in
     the current environment list.  If the variable name does not exist in the
     list, it is inserted with the given value. If the variable does exist,
     the argument overwrite is tested; if overwrite is zero, the variable is
     not reset, otherwise it is reset to the given value.

     The putenv() function takes an argument of the form ``name=value'' and is
     equivalent to:

           setenv(name, value, 1);

     The unsetenv() function deletes all instances of the variable name point-
     ed to by name from the list.


RETURN VALUES

     The functions setenv() and putenv() return zero if successful; otherwise
     the global variable errno is set to indicate the error and a -1 is re-
     turned.


ERRORS

     [ENOMEM]      The function setenv() or putenv() failed because they were
                   unable to allocate memory for the environment.


SEE ALSO

     csh(1),  sh(1),  execve(2),  environ(7)


STANDARDS

     The getenv() function conforms to ANSI X3.159-1989 (``ANSI C'').


HISTORY

     The functions setenv() and unsetenv() appeared in Version 7 AT&T UNIX.
     The putenv() function appeared in 4.3BSD-Reno.

4.4BSD                           June 29, 1991                               1