GETENV(3) MachTen 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 un-
able to allocate memory for the environment.
SEE ALSO
csh(1), sh(1), execve(2), environ(7)
STANDARDS
The getenv() function conforms to ANSI C3.159-1989
(‘‘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 December 11, 1993 1