confstr(3) Library Functions Manual confstr(3)
NAME
confstr - get configuration dependent string variables
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#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_SOURCE
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 sys-
tem (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 de-
fined 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
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 is set to
EINVAL.
ERRORS
EINVAL The value of name is invalid.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│ confstr() │ Thread safety │ MT-Safe │
└────────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
POSIX.1-2008.
HISTORY
POSIX.1-2001.
EXAMPLES
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
getconf(1), sh(1), exec(3), fpathconf(3), pathconf(3), sysconf(3), sys-
tem(3)
Linux man-pages 6.9.1 2024-06-15 confstr(3)
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