realpath (3p) - Linux Manuals

realpath: resolve a pathname

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 names the same file, whose resolution does not involve '.', '..', or symbolic links. 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 a null pointer, the behavior of realpath() is implementation-defined.

RETURN VALUE

Upon successful completion, realpath() shall return a pointer to the resolved name. Otherwise, realpath() shall return a null pointer and set errno to indicate the error, and the contents of the buffer pointed to by resolved_name are undefined.

ERRORS

The realpath() function shall fail if:

EACCES

Read or search permission was denied for a component 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 path argument.

ENAMETOOLONG

The length of the file_name argument exceeds {PATH_MAX} or a pathname component 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 is not a directory.

The realpath() function may fail if:

ELOOP

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

ENAMETOOLONG

Pathname resolution of a symbolic link produced an intermediate result whose length 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 actualpath array.

#include <stdlib.h>
...
char *symlinkpath = "/tmp/symlink/file";
char actualpath [PATH_MAX+1];
char *ptr;


ptr = realpath(symlinkpath, actualpath);

APPLICATION USAGE

None.

RATIONALE

Since the maximum pathname length is arbitrary unless {PATH_MAX} is defined, an application generally cannot supply a resolved_name buffer with size {{PATH_MAX}+1}.

FUTURE DIRECTIONS

In the future, passing a null pointer to realpath() for the resolved_name argument may be defined to have realpath() allocate space for the generated pathname.

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .