confstr - get configuration dependent string variables

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ confstr()                                                                   │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

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.

EINVAL The value of name is invalid.

       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);

       POSIX.1-2001.

       Standard C library (libc, -lc)

       confstr - get configuration dependent string variables

       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.

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

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

       POSIX.1-2008.

#include<unistd.h>size_tconfstr(intname,charbuf[.size],size_tsize);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       confstr():
           _POSIX_C_SOURCE >= 2 || _XOPEN_SOURCE