NAME

       realpath - return the canonicalized absolute pathname

SYNOPSIS

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

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

DESCRIPTION

       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.

RETURN VALUE

       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.

ERRORS

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

       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 pathname.

       ENAMETOOLONG
              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.

       ENOTDIR
              A component of the path prefix is not a directory.

BUGS

       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.

HISTORY

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

CONFORMING TO

       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;
              #else
                path_max = pathconf (path, _PC_PATH_MAX);
                if (path_max <= 0)
                  path_max = 4096;
              #endif

       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.

SEE ALSO

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

                                                 24 August 1999                                      REALPATH(3)