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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.

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);

SEE ALSO

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

COLOPHON

   This page is part of release 4.09 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/.



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