getenv, putenv, setenv, unsetenv - environment variable
functions
#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);
These functions set, unset, and fetch environment variables
from the host
environment list. For compatibility with differing environment conventions,
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 variable,
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 pointed
to by name from the list.
The functions setenv() and putenv() return zero if successful; otherwise
the global variable errno is set to indicate the error and
-1 is returned.
If getenv() is successful, the string returned should be
considered readonly.
[ENOMEM] The function setenv() or putenv() failed because
they were unable
to allocate memory for the environment.
csh(1), sh(1), execve(2), environ(7)
The getenv() function conforms to ANSI X3.159-1989 (``ANSI
C'').
The functions setenv() and unsetenv() appeared in Version 7
AT&T UNIX.
The putenv() function appeared in 4.3BSD-Reno.
OpenBSD 3.6 December 11, 1993
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