Originální popis anglicky:
realpath - return the canonicalized absolute pathname
Návod, kniha: Linux Programmer's Manual
#include <limits.h>
#include <stdlib.h>
char *realpath(const char *path, char *resolved_path);
realpath expands all symbolic links and resolves references to
'/./',
'/../' and extra
'/' characters in the null
terminated string named by
path and stores the canonicalized absolute
pathname in the buffer of size
PATH_MAX named by
resolved_path.
The resulting path will have no symbolic link,
'/./' or
'/../'
components.
If there is no error, it returns a pointer to the
resolved_path.
Otherwise it returns a NULL pointer, and the contents of the array
resolved_path are undefined. The global variable
errno is set to
indicate the error.
- EACCES
- Read or search permission was denied for a component of the
path prefix.
- EINVAL
- Either path or resolved_path is NULL. (In
libc5 this would just cause a segfault.)
- EIO
- An I/O error occurred while reading from the file
system.
- ELOOP
- Too many symbolic links were encountered in translating the
pathname.
- ENAMETOOLONG
- A component of a path name exceeded NAME_MAX
characters, or an entire path name exceeded PATH_MAX
characters.
- ENOENT
- The named file does not exist.
- ENOTDIR
- A component of the path prefix is not a directory.
Never use this function. It is broken by design since it is impossible to
determine a suitable size for the output buffer. According to POSIX a buffer
of size PATH_MAX suffices, but PATH_MAX need not be a defined constant, and
may have to be obtained using
pathconf(). And asking
pathconf()
does not really help, since on the one hand POSIX warns that the result of
pathconf() may be huge and unsuitable for mallocing memory. And on the
other hand
pathconf() may return -1 to signify that PATH_MAX is not
bounded.
The libc4 and libc5 implementation contains a buffer overflow (fixed in
libc-5.4.13). Thus, suid programs like mount need a private version.
The
realpath function first appeared in BSD 4.4, contributed by Jan-Simon
Pendry. In Linux this function appears in libc 4.5.21.
In BSD 4.4 and Solaris the limit on the pathname length is MAXPATHLEN (found in
<sys/param.h>). The SUSv2 prescribes PATH_MAX and NAME_MAX, as found in
<limits.h> or provided by the
pathconf() 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 BSD 4.4, Linux and SUSv2 versions always return an absolute path name.
Solaris may return a relative path name when the
path argument is
relative. The prototype of
realpath is given in <unistd.h> in
libc4 and libc5, but in <stdlib.h> everywhere else.
readlink(2),
getcwd(3),
pathconf(3),
sysconf(3)
