confstr(3)                                            Library Functions Manual                                           confstr(3)

       confstr - get configuration dependent string variables

       Standard C library (libc, -lc)

       #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)):

           _POSIX_C_SOURCE >= 2 || _XOPEN_SOURCE

       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 "linux‐

              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 nec‐
       essary,  with  a  null  byte  ('\0') as terminator.  This can be detected by comparing the return value of confstr() against

       If size is zero and buf is NULL, confstr() just returns the value as defined below.

       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.

       EINVAL The value of name is invalid.

       For an explanation of the terms used in this section, see attributes(7).

       │Interface                                                                                        │ Attribute     │ Value   │
       │confstr()                                                                                        │ Thread safety │ MT-Safe │

       POSIX.1-2001, POSIX.1-2008.

       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)
           confstr(_CS_PATH, pathbuf, n);

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

Linux man-pages 6.03                                         2023-02-05                                                  confstr(3)