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 5.13 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/.