NAME
realpath - return the canonicalized absolute pathname
SYNOPSIS
#include <limits.h>
#include <stdlib.h>
char *realpath(const char *path, char *resolved_path);
DESCRIPTION
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.
RETURN VALUE
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.
ERRORS
EACCES
Read or sear.h 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.
BUGS
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 length of the output buffer should have been an additional
parameter, especially since
pathconf(3)
warns that the result of
pathconf()
may be huge and unsuitable for mallocing memory.
HISTORY
The
realpath
function first appeared in BSD 4.4, contributed by Jan-Simon Pendry.
In Linux this function appears in libc 4.5.21.
CONFORMING TO
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
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.
SEE ALSO
readlink(2),
getcwd(3),
pathconf(3),
sysconf(3)
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#include <stdio.h>
#include <string.h>
#include <sys/syslimits.h>
int main(int atgc, char *argv[])
{
char buff[PATH_MAX];
printf("realpath: [%s]->[%s]",argv[1],realpath(argv[1],buff));
return(0);
}
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