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



NAME
       realpath - return the canonicalized absolute pathname

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

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

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

       realpath():
           _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

DESCRIPTION
       realpath()  expands  all symbolic links and resolves references to /./, /../ and extra '/'
       characters in the null-terminated string named by path to produce a canonicalized absolute
       pathname.   The  resulting pathname is stored as a null-terminated string, up to a maximum
       of PATH_MAX bytes, in the buffer pointed to by resolved_path.   The  resulting  path  will
       have no symbolic link, /./ or /../ components.

       If resolved_path is specified as NULL, then realpath() uses malloc(3) to allocate a buffer
       of up to PATH_MAX bytes to hold the resolved pathname, and returns a pointer to this  buf‐
       fer.  The caller should deallocate this buffer using free(3).

RETURN VALUE
       If there is no error, realpath() returns a pointer to the resolved_path.

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

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

       EINVAL path is NULL.  (In glibc versions before  2.3,  this  error  is  also  returned  if
              resolved_path is NULL.)

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

       ELOOP  Too many symbolic links were encountered in translating the pathname.

       ENAMETOOLONG
              A  component  of  a  pathname  exceeded  NAME_MAX characters, or an entire pathname
              exceeded PATH_MAX characters.

       ENOENT The named file does not exist.

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

CONFORMING TO
       4.4BSD, POSIX.1-2001.

       POSIX.1-2001 says that the behavior if resolved_path is  NULL  is  implementation-defined.
       POSIX.1-2008 specifies the behavior described in this page.

NOTES
       In  4.4BSD  and  Solaris,  the  limit  on  the  pathname  length  is  MAXPATHLEN (found in
       <sys/param.h>).  SUSv2 prescribes PATH_MAX and NAME_MAX, as found in  <limits.h>  or  pro‐
       vided by the pathconf(3) 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

       (But see the BUGS section.)

   GNU extensions
       If  the  call  fails  with either EACCES or ENOENT and resolved_path is not NULL, then the
       prefix of path that is not readable or does not exist is returned in resolved_path.

BUGS
       The POSIX.1-2001 standard version of this function is broken by design, since it is impos‐
       sible  to  determine  a  suitable size for the output buffer, resolved_path.  According to
       POSIX.1-2001 a buffer of size PATH_MAX suffices, but PATH_MAX need not be a  defined  con‐
       stant,  and  may  have  to be obtained using pathconf(3).  And asking pathconf(3) does not
       really help, since, on the one hand POSIX warns that the result of pathconf(3) may be huge
       and  unsuitable  for  mallocing memory, and on the other hand pathconf(3) may return -1 to
       signify that PATH_MAX is not bounded.  The resolved_path == NULL feature, not standardized
       in  POSIX.1-2001,  but  standardized  in  POSIX.1-2008,  allows  this design problem to be
       avoided.

SEE ALSO
       realpath(1), readlink(2), canonicalize_file_name(3), getcwd(3), pathconf(3), sysconf(3)

COLOPHON
       This page is part of release 3.74 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.



                                            2014-10-02                                REALPATH(3)