let $attr{symlink} return the last element of the path

[elogind.git] / udev_sysfs.c

diff --git a/udev_sysfs.c b/udev_sysfs.c
index c1926966896849c827916402f72312c17e02c190..e733d417c5628854ee5f1d4f06b463873a1d0944 100644 (file)
--- a/udev_sysfs.c
+++ b/udev_sysfs.c
@@ -346,6 +346,7 @@ char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
        char value[NAME_SIZE];
        struct sysfs_attr *attr_loop;
        struct sysfs_attr *attr;
+       struct stat statbuf;
        int fd;
        ssize_t size;
        size_t sysfs_len;
@@ -375,25 +376,48 @@ char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
        dbg("add to cache '%s'", path_full);
        list_add(&attr->node, &attr_list);
 
-       /* read attribute value */
-       fd = open(path_full, O_RDONLY);
-       if (fd < 0) {
-               dbg("attribute '%s' does not exist", path_full);
+       if (lstat(path_full, &statbuf) != 0) {
+               dbg("stat '%s' failed: %s", path_full, strerror(errno));
                goto out;
        }
-       size = read(fd, value, sizeof(value));
-       close(fd);
-       if (size < 0)
-               goto out;
-       if (size == sizeof(value))
-               goto out;
 
-       /* got a valid value, store and return it */
-       value[size] = '\0';
-       remove_trailing_chars(value, '\n');
-       dbg("cache '%s' with value '%s'", path_full, value);
-       strlcpy(attr->value_local, value, sizeof(attr->value_local));
-       attr->value = attr->value_local;
+       if (S_ISLNK(statbuf.st_mode)) {
+               /* links return the last element of the target path */
+               char link_target[PATH_SIZE];
+               int len;
+               const char *pos;
+
+               len = readlink(path_full, link_target, sizeof(link_target));
+               if (len > 0) {
+                       link_target[len] = '\0';
+                       pos = strrchr(link_target, '/');
+                       if (pos != NULL) {
+                               dbg("cache '%s' with link value '%s'", path_full, value);
+                               strlcpy(attr->value_local, &pos[1], sizeof(attr->value_local));
+                               attr->value = attr->value_local;
+                       }
+               }
+       } else {
+               /* read attribute value */
+               fd = open(path_full, O_RDONLY);
+               if (fd < 0) {
+                       dbg("attribute '%s' does not exist", path_full);
+                       goto out;
+               }
+               size = read(fd, value, sizeof(value));
+               close(fd);
+               if (size < 0)
+                       goto out;
+               if (size == sizeof(value))
+                       goto out;
+
+               /* got a valid value, store and return it */
+               value[size] = '\0';
+               remove_trailing_chars(value, '\n');
+               dbg("cache '%s' with attribute value '%s'", path_full, value);
+               strlcpy(attr->value_local, value, sizeof(attr->value_local));
+               attr->value = attr->value_local;
+       }
 
 out:
        return attr->value;