confstr - get configuration dependent string variables
Standard C library (
libc,
-lc)
#include <unistd.h>
size_t confstr(int name, char buf[.size], size_t size);
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
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.
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.
- 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)