confstr - get configuration dependent string variables
#include <unistd.h>
size_t confstr(int name, char *buf, size_t len);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
confstr(): _POSIX_C_SOURCE >= 2 || _XOPEN_SOURCE
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 bytes 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.
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.
- EINVAL
- The value of name is invalid.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
confstr () |
Thread safety |
MT-Safe |
POSIX.1-2001, POSIX.1-2008.
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);
getconf(1),
sh(1),
exec(3),
fpathconf(3),
pathconf(3),
sysconf(3),
system(3)