PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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         top

       realpath — resolve a pathname

SYNOPSIS         top

       #include <stdlib.h>

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

DESCRIPTION         top

       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         top

       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         top

       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         top

   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         top

       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         top

       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         top

       None.

SEE ALSO         top

       fpathconf(3p), free(3p), getcwd(3p), sysconf(3p)

       The Base Definitions volume of POSIX.1‐2008, limits.h(0p),
       stdlib.h(0p)

COPYRIGHT         top

       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 .

IEEE/The Open Group                 2013                        REALPATH(3P)