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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | VERSIONS | STANDARDS | HISTORY | BUGS | SEE ALSO | COLOPHON |
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realpath(3) Library Functions Manual realpath(3)
realpath - return the canonicalized absolute pathname
Standard C library (libc, -lc)
#include <limits.h>
#include <stdlib.h>
char *realpath(const char *restrict path,
char *restrict resolved_path);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
realpath():
_XOPEN_SOURCE >= 500
|| /* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE
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.
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 resolved_path 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.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│ realpath() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
GNU extensions
If the call fails with either EACCES or ENOENT and resolved_path
is not NULL, then the prefix of path that is not readable or does
not exist is returned in resolved_path.
POSIX.1-2008.
4.4BSD, POSIX.1-2001, Solaris.
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.
realpath(1), readlink(2), canonicalize_file_name(3), getcwd(3),
pathconf(3), sysconf(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.15 2025-05-17 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)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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