realpath — return the canonicalized absolute pathname
#include <limits.h> #include <stdlib.h>
char
*realpath( |
const char *path, |
char *resolved_path); |
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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).
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.
Read or search permission was denied for a component of the path prefix.
path is
NULL. (In glibc versions before 2.3, this error is also
returned if resolved_path is
NULL.)
An I/O error occurred while reading from the filesystem.
Too many symbolic links were encountered in translating the pathname.
A component of a pathname exceeded NAME_MAX characters, or an entire
pathname exceeded PATH_MAX characters.
Out of memory.
The named file does not exist.
A component of the path prefix is not a directory.
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
realpath() |
Thread safety | MT-Safe |
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.
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.)
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.
This page is part of release 4.00 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
http://www.kernel.org/doc/man−pages/.
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Copyright (C) 1999 Andries Brouwer (aebcwi.nl) %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END Rewritten old page, 990824, aebcwi.nl 2004-12-14, mtk, added discussion of resolved_path == NULL |