REALPATH(3)                 Linux Programmer's Manual                REALPATH(3)

       realpath - return the canonicalized absolute pathname

       #include <limits.h>
       #include <stdlib.h>

       char *realpath(const char *path, char *resolved_path);

       realpath expands all symbolic links and resolves references to '/./',
       '/../' and extra '/' characters in the null terminated string named by
       path and stores the canonicalized absolute pathname in the buffer of size
       PATH_MAX named by resolved_path.  The resulting path will have no
       symbolic link, '/./' or '/../' components.

       If there is no error, it returns a pointer to the resolved_path.

       Otherwise it returns a NULL pointer, and the contents of the array
       resolved_path are undefined. The global variable errno is set to indicate
       the error.

       EACCES Read or search permission was denied for a component of the path

       EINVAL Either path or resolved_path is NULL. (In libc5 this would just
              cause a segfault.)

       EIO    An I/O error occurred while reading from the file system.

       ELOOP  Too many symbolic links were encountered in translating the

              A component of a path name exceeded NAME_MAX characters, or an
              entire path name exceeded PATH_MAX characters.

       ENOENT The named file does not exist.

              A component of the path prefix is not a directory.

       The libc4 and libc5 implementation contains a buffer overflow (fixed in
       libc-5.4.13).  Thus, suid programs like mount need a private version.

       The length of the output buffer should have been an additional parameter,
       especially since pathconf(3) warns that the result of pathconf() may be
       huge and unsuitable for mallocing memory.

       The realpath function first appeared in BSD 4.4, contributed by Jan-Simon
       Pendry.  In Linux this function appears in libc 4.5.21.

       In BSD 4.4 and Solaris the limit on the pathname length is MAXPATHLEN
       (found in <sys/param.h>). The SUSv2 prescribes PATH_MAX and NAME_MAX, as
       found in <limits.h> or provided by the pathconf() function. A typical
       source fragment would be

              #ifdef PATH_MAX
                path_max = PATH_MAX;
                path_max = pathconf (path, _PC_PATH_MAX);
                if (path_max <= 0)
                  path_max = 4096;

       The BSD 4.4, Linux and SUSv2 versions always return an absolute path
       name. Solaris may return a relative path name when the path argument is
       relative.  The prototype of realpath is given in <unistd.h> in libc4 and
       libc5, but in <stdlib.h> everywhere else.

       readlink(2), getcwd(3), pathconf(3), sysconf(3)

                                 24 August 1999                      REALPATH(3)