realpath(3) - Linux manual page (original) (raw)
realpath(3) Library Functions Manual realpath(3)
NAME top
realpath - return the canonicalized absolute pathnameLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <limits.h>**
**#include <stdlib.h>**
**char *realpath(const char *restrict** _path_**,**
**char *restrict** _resolvedpath_**);**Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
**realpath**():
_XOPEN_SOURCE >= 500
|| /* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCEDESCRIPTION top
**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
_resolvedpath_. The resulting path will have no symbolic link, _/./_
or _/../_ components.
If _resolvedpath_ is specified as NULL, then **realpath**() uses
[malloc(3)](../man3/malloc.3.html) 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)](../man3/free.3.html).RETURN VALUE top
If there is no error, **realpath**() returns a pointer to the
_resolvedpath_.
Otherwise, it returns NULL, the contents of the array
_resolvedpath_ are undefined, and _[errno](../man3/errno.3.html)_ is set to indicate the
error.ERRORS top
**EACCES** Read or search permission was denied for a component of the
path prefix.
**EINVAL** _path_ is NULL. (Before glibc 2.3, this error is also
returned if _resolvedpath_ is NULL.)
**EIO** An I/O error occurred while reading from the filesystem.
**ELOOP** Too many symbolic links were encountered in translating the
pathname.
**ENAMETOOLONG**
A component of a pathname exceeded **NAME_MAX** characters, or
an entire pathname exceeded **PATH_MAX** characters.
**ENOENT** The named file does not exist.
**ENOMEM** Out of memory.
**ENOTDIR**
A component of the path prefix is not a directory.ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ **Interface** │ **Attribute** │ **Value** │
├──────────────────────────────────────┼───────────────┼─────────┤
│ **realpath**() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘VERSIONS top
GNU extensions If the call fails with either EACCES or ENOENT and resolvedpath is not NULL, then the prefix of path that is not readable or does not exist is returned in resolvedpath.
STANDARDS top
POSIX.1-2008.HISTORY top
4.4BSD, POSIX.1-2001, Solaris.
POSIX.1-2001 says that the behavior if _resolvedpath_ 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)](../man3/pathconf.3.html) 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.)BUGS top
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, _resolvedpath_. 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)](../man3/pathconf.3.html).
And asking [pathconf(3)](../man3/pathconf.3.html) does not really help, since, on the one
hand POSIX warns that the result of [pathconf(3)](../man3/pathconf.3.html) may be huge and
unsuitable for mallocing memory, and on the other hand [pathconf(3)](../man3/pathconf.3.html)
may return -1 to signify that **PATH_MAX** is not bounded. The
_resolvedpath == NULL_ feature, not standardized in POSIX.1-2001,
but standardized in POSIX.1-2008, allows this design problem to be
avoided.SEE ALSO top
[realpath(1)](../man1/realpath.1.html), [readlink(2)](../man2/readlink.2.html), [canonicalize_file_name(3)](../man3/canonicalize%5Ffile%5Fname.3.html), [getcwd(3)](../man3/getcwd.3.html),
[pathconf(3)](../man3/pathconf.3.html), [sysconf(3)](../man3/sysconf.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 realpath(3)
Pages that refer to this page:dpkg-shlibdeps(1), readlink(1), realpath(1), mount(2), readlink(2), bindtextdomain(3), canonicalize_file_name(3), matchpathcon(3), selinux_restorecon(3), mount(8), restorecon(8)