confstr(3) — Linux manual page


CONFSTR(3)                Linux Programmer's Manual               CONFSTR(3)

NAME         top

       confstr - get configuration dependent string variables

SYNOPSIS         top

       #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

DESCRIPTION         top

       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").

              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.

RETURN VALUE         top

       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.

ERRORS         top

       EINVAL The value of name is invalid.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface Attribute     Value   │
       │confstr() │ Thread safety │ MT-Safe │

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008.

EXAMPLES         top

       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)
           confstr(_CS_PATH, pathbuf, n);

SEE ALSO         top

       getconf(1), sh(1), exec(3), fpathconf(3), pathconf(3), sysconf(3),

COLOPHON         top

       This page is part of release 5.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

GNU                              2020-06-09                       CONFSTR(3)

Pages that refer to this page: fpathconf(3)gnu_get_libc_release(3)gnu_get_libc_version(3)pathconf(3)sysconf(3)posixoptions(7)standards(7)