| .\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de) |
| .\" |
| .\" %%%LICENSE_START(VERBATIM) |
| .\" Permission is granted to make and distribute verbatim copies of this |
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| .\" preserved on all copies. |
| .\" |
| .\" Permission is granted to copy and distribute modified versions of this |
| .\" manual under the conditions for verbatim copying, provided that the |
| .\" entire resulting derived work is distributed under the terms of a |
| .\" permission notice identical to this one. |
| .\" |
| .\" 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| .\" manual page may be incorrect or out-of-date.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 |
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| .\" Formatted or processed versions of this manual, if unaccompanied by |
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| .\" %%%LICENSE_END |
| .\" |
| .\" 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 2020-06-09 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| confstr \- get configuration dependent string variables |
| .SH SYNOPSIS |
| .nf |
| .B #include <unistd.h> |
| .PP |
| .BI "size_t confstr(int " "name" ", char *" buf ", size_t " len ); |
| .fi |
| .PP |
| .in -4n |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .in |
| .PP |
| .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\e0\(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. |
| .PP |
| 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 |
| The value of |
| .I name |
| is invalid. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .TS |
| allbox; |
| lb lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR confstr () |
| T} Thread safety MT-Safe |
| .TE |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008. |
| .SH EXAMPLES |
| The following code fragment determines the path where to find |
| the POSIX.2 system utilities: |
| .PP |
| .in +4n |
| .EX |
| 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); |
| .EE |
| .in |
| .SH SEE ALSO |
| .BR getconf (1), |
| .BR sh (1), |
| .BR exec (3), |
| .BR fpathconf (3), |
| .BR pathconf (3), |
| .BR sysconf (3), |
| .BR system (3) |