REALPATH(3P)						     POSIX Programmer's Manual						      REALPATH(3P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing 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 Technol-
       ogy  --	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 Stan-
       dard 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 .

IEEE
/The Open Group						       2013							      REALPATH(3P)