minimal realpath implementation using /proc

clean and simple, but fails when the caller does not have permissions
to open the file for reading or when /proc is not available. i may
replace this with a full implementation later, possibly leaving this
version as an optimization to use when it works.
This commit is contained in:
Rich Felker 2011-04-17 17:32:36 -04:00
parent 2afed79f15
commit e98bdca9df
1 changed files with 43 additions and 0 deletions

View File

@ -1,6 +1,49 @@
#include <stdlib.h>
#include <stdio.h>
#include <limits.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
char *realpath(const char *filename, char *resolved)
{
int fd;
ssize_t r;
struct stat st1, st2;
char buf[15+3*sizeof(int)];
int alloc = 0;
if (!filename) {
errno = EINVAL;
return 0;
}
if (!resolved) {
alloc = 1;
resolved = malloc(PATH_MAX);
if (!resolved) return 0;
}
fd = open(filename, O_RDONLY|O_NONBLOCK);
if (fd < 0) return 0;
snprintf(buf, sizeof buf, "/proc/self/fd/%d", fd);
r = readlink(buf, resolved, PATH_MAX-1);
if (r < 0) goto err;
resolved[r] = 0;
fstat(fd, &st1);
r = stat(resolved, &st2);
if (r<0 || st1.st_dev != st2.st_dev || st1.st_ino != st2.st_ino) {
if (!r) errno = ELOOP;
goto err;
}
close(fd);
return resolved;
err:
if (alloc) free(resolved);
close(fd);
return 0;
}