/* vi: set sw=4 ts=4: */
/*
- * xreadlink.c - safe implementation of readlink.
- * Returns a NULL on failure...
+ * xreadlink.c - safe implementation of readlink.
+ * Returns a NULL on failure...
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
*/
#include "libbb.h"
+/* some systems (eg Hurd) does not have MAXSYMLINKS definition,
+ * set it to some reasonable value if it isn't defined */
+#ifndef MAXSYMLINKS
+# define MAXSYMLINKS 20
+#endif
+
/*
* NOTE: This function returns a malloced char* that you will have to free
- * yourself. You have been warned.
+ * yourself.
*/
-char *xmalloc_readlink(const char *path)
+char* FAST_FUNC xmalloc_readlink(const char *path)
{
enum { GROWBY = 80 }; /* how large we will grow strings by */
}
/*
- * this routine is not the same as realpath(), which canonicalizes
- * the given path completely. this routine only follows trailing
- * symlinks until a real file is reached, and returns its name.
- * intermediate symlinks are not expanded. as above, a malloced
- * char* is returned, which must be freed.
+ * This routine is not the same as realpath(), which
+ * canonicalizes the given path completely. This routine only
+ * follows trailing symlinks until a real file is reached and
+ * returns its name. If the path ends in a dangling link or if
+ * the target doesn't exist, the path is returned in any case.
+ * Intermediate symlinks in the path are not expanded -- only
+ * those at the tail.
+ * A malloced char* is returned, which must be freed by the caller.
*/
-char *xmalloc_readlink_follow(const char *path)
+char* FAST_FUNC xmalloc_follow_symlinks(const char *path)
{
- char *buf = NULL, *lpc, *linkpath;
+ char *buf;
+ char *lpc;
+ char *linkpath;
int bufsize;
- smallint looping = 0;
+ int looping = MAXSYMLINKS + 1;
- buf = strdup(path);
- bufsize = strlen(path) + 1;
+ buf = xstrdup(path);
+ goto jump_in;
- while(1) {
+ while (1) {
linkpath = xmalloc_readlink(buf);
if (!linkpath) {
- if (errno == EINVAL) /* not a symlink */
+ /* not a symlink, or doesn't exist */
+ if (errno == EINVAL || errno == ENOENT)
return buf;
+ goto free_buf_ret_null;
+ }
+
+ if (!--looping) {
+ free(linkpath);
+ free_buf_ret_null:
free(buf);
return NULL;
- }
+ }
- if (*linkpath == '/') {
- free(buf);
- buf = linkpath;
- bufsize = strlen(linkpath) + 1;
- } else {
+ if (*linkpath != '/') {
bufsize += strlen(linkpath);
- if (looping++ > MAXSYMLINKS) {
- free(linkpath);
- free(buf);
- return NULL;
- }
buf = xrealloc(buf, bufsize);
lpc = bb_get_last_path_component_strip(buf);
strcpy(lpc, linkpath);
free(linkpath);
+ } else {
+ free(buf);
+ buf = linkpath;
+ jump_in:
+ bufsize = strlen(buf) + 1;
}
}
-
}
-char *xmalloc_readlink_or_warn(const char *path)
+char* FAST_FUNC xmalloc_readlink_or_warn(const char *path)
{
char *buf = xmalloc_readlink(path);
if (!buf) {
/* EINVAL => "file: Invalid argument" => puzzled user */
- bb_error_msg("%s: cannot read link (not a symlink?)", path);
+ const char *errmsg = "not a symlink";
+ int err = errno;
+ if (err != EINVAL)
+ errmsg = strerror(err);
+ bb_error_msg("%s: cannot read link: %s", path, errmsg);
}
return buf;
}
-/* UNUSED */
-#if 0
-char *xmalloc_realpath(const char *path)
+char* FAST_FUNC xmalloc_realpath(const char *path)
{
-#if defined(__GLIBC__) && !defined(__UCLIBC__)
+#if defined(__GLIBC__) || \
+ (defined(__UCLIBC__) && UCLIBC_VERSION >= KERNEL_VERSION(0, 9, 31))
/* glibc provides a non-standard extension */
+ /* new: POSIX.1-2008 specifies this behavior as well */
return realpath(path, NULL);
#else
char buf[PATH_MAX+1];
- /* on error returns NULL (xstrdup(NULL) ==NULL) */
+ /* on error returns NULL (xstrdup(NULL) == NULL) */
return xstrdup(realpath(path, buf));
#endif
}
-#endif