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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 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 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.

EXAMPLE

     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);