CONFSTR(3) Linux Programmer's Manual CONFSTR(3)
confstr - get configuration dependent string variables
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 sup-
_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
_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").
A value for the PATH variable which indicates where all the POSIX.2 standard utili-
ties 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 (includ-
ing 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 trun-
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, conf-
str() returns 0, and errno is set to EINVAL.
EINVAL If the value of name is invalid.
The following code fragment determines the path where to find the POSIX.2 system utili-
n = confstr(_CS_PATH, NULL, (size_t) 0);
pathbuf = malloc(n);
if (pathbuf == NULL)
confstr(_CS_PATH, pathbuf, n);
sh(1), exec(3), system(3)
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GNU 2012-05-10 CONFSTR(3)