confstr(3) — Linux manual page

confstr(3)              Library Functions Manual              confstr(3)

NAME

       confstr - get configuration dependent string variables

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <unistd.h>

       size_t confstr(int name, char buf[.size], size_t size);

   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 size is not zero, confstr() copies the
       value of the string to buf truncated to size - 1 bytes if
       necessary, with a null byte ('\0') as terminator.  This can be
       detected by comparing the return value of confstr() against size.

       If size 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 size, 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 │
       └─────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       POSIX.1-2008.

HISTORY

       POSIX.1-2001.

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

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Linux man-pages 6.9.1          2024-06-15                     confstr(3)

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

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