PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

NAME

       realpath — resolve a pathname

SYNOPSIS

       #include <stdlib.h>

       char *realpath(const char *restrict file_name,
           char *restrict resolved_name);

DESCRIPTION

       The  realpath()  function  shall  derive, from the pathname pointed to by file_name, an absolute pathname
       that resolves to the same directory entry, whose resolution does  not  involve  '.',  '..',  or  symbolic
       links.  If  resolved_name  is a null pointer, the generated pathname shall be stored as a null-terminated
       string in a buffer allocated as if by a call to malloc().  Otherwise,  if  {PATH_MAX}  is  defined  as  a
       constant  in  the  <limits.h>  header,  then  the generated pathname shall be stored as a null-terminated
       string, up to a maximum of {PATH_MAX} bytes, in the buffer pointed to by resolved_name.

       If resolved_name is not a null pointer and {PATH_MAX} is not defined as  a  constant  in  the  <limits.h>
       header, the behavior is undefined.

RETURN VALUE

       Upon successful completion, realpath() shall return a pointer to the buffer containing the resolved name.
       Otherwise, realpath() shall return a null pointer and set errno to indicate the error.

       If the resolved_name argument is a null pointer, the pointer returned by  realpath()  can  be  passed  to
       free().

       If  the  resolved_name  argument is not a null pointer and the realpath() function fails, the contents of
       the buffer pointed to by resolved_name are undefined.

ERRORS

       The realpath() function shall fail if:

       EACCES Search permission was denied for a component of the path prefix of file_name.

       EINVAL The file_name argument is a null pointer.

       EIO    An error occurred while reading from the file system.

       ELOOP  A loop exists in symbolic links encountered during resolution of the file_name argument.

       ENAMETOOLONG
              The length of a component of a pathname is longer than {NAME_MAX}.

       ENOENT A component of file_name does not name an existing file or file_name points to an empty string.

       ENOTDIR
              A component of the path prefix names an existing file that is neither a directory nor  a  symbolic
              link  to  a  directory,  or the file_name argument contains at least one non-<slash> character and
              ends with one or more trailing <slash>  characters  and  the  last  pathname  component  names  an
              existing file that is neither a directory nor a symbolic link to a directory.

       The realpath() function may fail if:

       EACCES The  file_name  argument  does  not  begin  with a <slash> and none of the symbolic links (if any)
              processed during pathname resolution of file_name had contents that  began  with  a  <slash>,  and
              either  search  permission  was  denied for the current directory or read or search permission was
              denied for a directory above the current directory in the file hierarchy.

       ELOOP  More than {SYMLOOP_MAX} symbolic  links  were  encountered  during  resolution  of  the  file_name
              argument.

       ENAMETOOLONG
              The length of a pathname exceeds {PATH_MAX}, or pathname resolution of a symbolic link produced an
              intermediate result with a length that exceeds {PATH_MAX}.

       ENOMEM Insufficient storage space is available.

       The following sections are informative.

EXAMPLES

   Generating an Absolute Pathname
       The following example generates an absolute pathname for the file identified by the symlinkpath argument.
       The generated pathname is stored in the buffer pointed to by actualpath.

           #include <stdlib.h>
           ...
           char *symlinkpath = "/tmp/symlink/file";
           char *actualpath;

           actualpath = realpath(symlinkpath, NULL);
           if (actualpath != NULL)
           {
               ... use actualpath ...

               free(actualpath);
           }
           else
           {
               ... handle error ...
           }

APPLICATION USAGE

       For  functions that allocate memory as if by malloc(), the application should release such memory when it
       is no longer required by a call to free().  For realpath(), this is the return value.

RATIONALE

       Since realpath() has no length argument, if {PATH_MAX} is  not  defined  as  a  constant  in  <limits.h>,
       applications  have  no  way  of determining how large a buffer they need to allocate for it to be safe to
       pass to realpath().  A {PATH_MAX} value obtained from a prior pathconf() call is out-of-date by the  time
       realpath()  is  called.  Hence  the only reliable way to use realpath() when {PATH_MAX} is not defined in
       <limits.h> is to pass a null pointer for resolved_name so that realpath() will allocate a buffer  of  the
       necessary size.

FUTURE DIRECTIONS

       None.

SEE ALSO

       fpathconf(), free(), getcwd(), sysconf()

       The Base Definitions volume of POSIX.1‐2008, <limits.h>, <stdlib.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications  Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
       and The Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In  the  event
       of  any  discrepancy between this version and the original IEEE and The Open Group Standard, the original
       IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at
       http://www.unix.org/online.html .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .