DESCRIPTION confstr() gets the value of configuration-dependent string variables.
_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 len is not zero, confstr() copies the value of the string to buf truncated to len - 1 characters if necessary, with a null byte (’ ’) as terminator. This can be detected by comparing the return value of confstr() against len.
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 len, which means that the value in buf is truncated.
ERRORS EINVAL If the value of name is invalid.