confstr(3) - Linux manual page (original) (raw)
confstr(3) Library Functions Manual confstr(3)
NAME top
confstr - get configuration dependent string variablesLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <unistd.h>**
**size_t confstr(int** _name_**, char** _buf_**[.**_size_**], size_t** _size_**);**Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
**confstr**():
_POSIX_C_SOURCE >= 2 || _XOPEN_SOURCEDESCRIPTION top
**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 _size_ is not zero, **confstr**() copies the
value of the string to _buf_ truncated to _size - 1_ bytes if
necessary, with a null byte ('\0') as terminator. This can be
detected by comparing the return value of **confstr**() against _size_.
If _size_ is zero and _buf_ is NULL, **confstr**() just returns the value
as defined below.RETURN VALUE top
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 _size_, 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](../man3/errno.3.html)_ is set to **EINVAL**.ERRORS top
**EINVAL** The value of _name_ is invalid.ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ **Interface** │ **Attribute** │ **Value** │
├──────────────────────────────────────┼───────────────┼─────────┤
│ **confstr**() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘STANDARDS top
POSIX.1-2008.HISTORY top
POSIX.1-2001.EXAMPLES top
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);
pathbuf = malloc(n);
if (pathbuf == NULL)
abort();
confstr(_CS_PATH, pathbuf, n);SEE ALSO top
**getconf**(1), **sh**(1), [exec(3)](../man3/exec.3.html), [fpathconf(3)](../man3/fpathconf.3.html), [pathconf(3)](../man3/pathconf.3.html), [sysconf(3)](../man3/sysconf.3.html),
[system(3)](../man3/system.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 confstr(3)
Pages that refer to this page:fpathconf(3), gnu_get_libc_version(3), sysconf(3), posixoptions(7), standards(7)