confstr.3, strcasecmp.3, strcat.3, strcmp.3, strcpy.3, strdup.3, strftime.3, strlen...

[thirdparty/man-pages.git] / man3 / confstr.3

.\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
.\"
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.\" manual under the conditions for verbatim copying, provided that the
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.\" manual page may be incorrect or out-of-date.  The author(s) assume no
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.\" 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
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.\" 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()
.TH CONFSTR 3  2010-02-03 "GNU" "Linux Programmer's Manual"
.SH NAME
confstr \- get configuration dependent string variables
.SH SYNOPSIS
.nf
.B #include <unistd.h>
.sp
.BI "size_t confstr(int " "name" ", char *" buf ", size_t " len );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR confstr ():
_POSIX_C_SOURCE\ >=\ 2 || _XOPEN_SOURCE
.SH DESCRIPTION
.BR confstr ()
gets the value of configuration-dependent string variables.
.PP
The
.I name
argument is the system variable to be queried.
The following variables are supported:
.TP
.BR _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").
.TP
.BR _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").
.TP
.B _CS_PATH
A value for the
.B PATH
variable which indicates where all the POSIX.2 standard utilities can
be found.
.PP
If
.I buf
is not NULL and
.I len
is not zero,
.BR confstr ()
copies the value of the string to
.I buf
truncated to
.I len \- 1
bytes if necessary, with a null byte (\(aq\\0\(aq) as terminator.
This can be detected by comparing the return value of
.BR confstr ()
against
.IR len .
.PP
If
.I len
is zero and
.I buf
is NULL,
.BR confstr ()
just returns the value as defined below.
.SH "RETURN VALUE"
If
.I name
is a valid configuration variable,
.BR 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
.IR len ,
which means that the value in
.I buf
is truncated.

If
.I name
is a valid configuration variable,
but that variable does not have a value, then
.BR confstr ()
returns 0.
If
.I name
does not correspond to a valid configuration variable,
.BR confstr ()
returns 0, and
.I errno
is set to
.BR EINVAL .
.SH ERRORS
.TP
.B EINVAL
If the value of
.I name
is invalid.
.SH "CONFORMING TO"
POSIX.1-2001.
.SH EXAMPLE
The following code fragment determines the path where to find
the POSIX.2 system utilities:
.br
.nf
.in +4n

char *pathbuf;
size_t n;

n = confstr(_CS_PATH,NULL,(size_t) 0);
pathbuf = malloc(n);
if (pathbuf == NULL)
    abort();
confstr(_CS_PATH, pathbuf, n);
.in
.fi
.SH "SEE ALSO"
.BR sh (1),
.BR exec (3),
.BR system (3)