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():
           _XOPEN_SOURCE >= 500
               || /* Glibc since 2.19: */ _DEFAULT_SOURCE
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE

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 buffer.  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.

       ENOMEM Out of memory.

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

ATTRIBUTES

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

       ┌───────────┬───────────────┬─────────┐
       │Interface  │ Attribute     │ Value   │
       ├───────────┼───────────────┼─────────┤
       │realpath() │ Thread safety │ MT-Safe │
       └───────────┴───────────────┴─────────┘

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 provided 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 impossible 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 constant, 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  5.05  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
       https://www.kernel.org/doc/man-pages/.

                                                   2017-09-15                                        REALPATH(3)