libbb/procps.c: make fast_strtoul_10() stop on '\n' too

[oweals/busybox.git] / libbb / xreadlink.c

diff --git a/libbb/xreadlink.c b/libbb/xreadlink.c
index 4d87b944d6d8489351c6462aa7236847d0408451..ec95af2229f1d94243e9071fce2d9d69276cad86 100644 (file)
--- a/libbb/xreadlink.c
+++ b/libbb/xreadlink.c
@@ -1,16 +1,18 @@
 /* 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"
 
 /*
  * 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 */
 
@@ -18,7 +20,8 @@ char *xmalloc_readlink(const char *path)
        int bufsize = 0, readsize = 0;
 
        do {
-               buf = xrealloc(buf, bufsize += GROWBY);
+               bufsize += GROWBY;
+               buf = xrealloc(buf, bufsize);
                readsize = readlink(path, buf, bufsize);
                if (readsize == -1) {
                        free(buf);
@@ -31,28 +34,82 @@ char *xmalloc_readlink(const char *path)
        return buf;
 }
 
-char *xmalloc_readlink_or_warn(const char *path)
+/*
+ * 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* FAST_FUNC xmalloc_follow_symlinks(const char *path)
+{
+       char *buf;
+       char *lpc;
+       char *linkpath;
+       int bufsize;
+       int looping = MAXSYMLINKS + 1;
+
+       buf = xstrdup(path);
+       goto jump_in;
+
+       while (1) {
+               linkpath = xmalloc_readlink(buf);
+               if (!linkpath) {
+                       /* 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 != '/') {
+                       bufsize += strlen(linkpath);
+                       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* 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__)
        /* 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