confstr

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



NAME
       confstr - get configuration dependent string variables

SYNOPSIS
       #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
       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.

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.

       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
       EINVAL The value of name is invalid.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                     Attribute     Value   │
       ├──────────────────────────────────────────────┼───────────────┼─────────┤
       │confstr()                                     │ Thread safety │ MT-Safe │
       └──────────────────────────────────────────────┴───────────────┴─────────┘

CONFORMING TO
       POSIX.1-2001, POSIX.1-2008.

EXAMPLES
       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);

SEE ALSO
       getconf(1), sh(1), exec(3), fpathconf(3), pathconf(3), sysconf(3),
       system(3)

COLOPHON
       This page is part of release 5.11 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
       https://www.kernel.org/doc/man-pages/.



GNU                                2021-03-22                         CONFSTR(3)