confstr(3) — Linux manual pages

Name

confstr — get configuration dependent string variables

Synopsis

#define _POSIX_C_SOURCE 2
or
#define _XOPEN_SOURCE
#include <unistd.h>

`size_t confstr(`	int	`name`,
	char *	`buf`,
	size_t	`len)`;

DESCRIPTION

confstr() gets the value of configuration-dependent string variables.

The name argument is the system variable to be queried. The following variables are supported:

_CS_GNU_LIBC_VERSION (GNU C library only; since glibc 2.3.2): A string which identifies the GNU C library version on this system (e.g, "glibc 2.3.4").
_CS_GNU_LIBPTHREAD_VERSION (GNU C library only; since glibc 2.3.2): A string which identifies the POSIX implementation supplied by this C library (e.g, "NPTL 2.3.4" or "linuxthreads-0.10").
_CS_PATH: A value for the PATH variable which indicates where all the POSIX.2 standard utilities can be found.

If buf is not NULL and len is not zero, confstr() copies the value of the string to buf truncated to len − 1 characters if necessary, with a null byte ('\0') as terminator. This can be detected by comparing the return value of confstr() against len.

If len is zero and buf is NULL, confstr() just returns the value as defined below.

RETURN VALUE

If name is a valid configuration variable, confstr() returns the number of bytes (including the terminating null byte) that would be required to hold the entire value of that variable. This value may be greater than len, which means that the value in buf is truncated.

If name is a valid configuration variable, but that variable does not have a value, then confstr() returns 0. If name does not correspond to a valid configuration variable, confstr() returns 0, and errno is set to EINVAL.

ERRORS

EINVAL: If the value of name is invalid.

CONFORMING TO

POSIX.1-2001

EXAMPLE

The following code fragment determines the path where to find the POSIX.2 system utilities:

char *pathbuf; size_t n;

n = confstr(_CS_PATH,NULL,(size_t) 0);
if ((pathbuf = malloc(n)) == NULL) abort();
confstr(_CS_PATH, pathbuf, n);

  (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)

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manual provided the copyright notice and this permission notice are
preserved on all copies.

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entire resulting derived work is distributed under the terms of a
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Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working
professionally.

Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.
License.
Modified Sat Jul 24 19:53:02 1993 by Rik Faith (faith@cs.unc.edu)
FIXME Many more values for 'name' are supported, some of which
are documented under 'info confstr'.
See <bits/confname.h> for the rest.
These should all be added to this page.
See also the POSIX.1-2001 specification of confstr()

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