Add readlink -m to show where a missing path would be.

Note: ubuntu will show -m through a file, this treat that as error.

3 files changed, 37 insertions, 24 deletions

diff --git a/lib/xwrap.c b/lib/xwrap.c
index 562cbaf4..54985db3 100644
--- a/lib/xwrap.c
+++ b/lib/xwrap.c
@@ -481,7 +481,7 @@ void xstat(char *path, struct stat *st)
 char *xabspath(char *path, int exact)
 {
   struct string_list *todo, *done = 0;
-  int try = 9999, dirfd = open("/", 0);;
+  int try = 9999, dirfd = open("/", 0), missing = 0;
   char *ret;
 
   // If this isn't an absolute path, start with cwd.
@@ -492,11 +492,12 @@ char *xabspath(char *path, int exact)
     free(temp);
   } else splitpath(path, &todo);
 
-  // Iterate through path components
+  // Iterate through path components in todo, prepend processed ones to done.
   while (todo) {
     struct string_list *new = llist_pop(&todo), **tail;
     ssize_t len;
 
+    // Eventually break out of endless loops
     if (!try--) {
       errno = ELOOP;
       goto error;
@@ -507,29 +508,37 @@ char *xabspath(char *path, int exact)
       int x = new->str[1];
 
       free(new);
-      if (x) {
-        if (done) free(llist_pop(&done));
-        len = 0;
-      } else continue;
+      if (!x) continue;
+      if (done) free(llist_pop(&done));
+      len = 0;
+
+      if (missing) missing--;
+      else {
+        if (-1 == (x = openat(dirfd, "..", 0))) goto error;
+        close(dirfd);
+        dirfd = x;
+      }
+      continue;
+    }
 
     // Is this a symlink?
-    } else len = readlinkat(dirfd, new->str, libbuf, sizeof(libbuf));
-
+    len = readlinkat(dirfd, new->str, libbuf, sizeof(libbuf));
     if (len>4095) goto error;
+
+    // Not a symlink: add to linked list, move dirfd, fail if error
     if (len<1) {
       int fd;
-      char *s = "..";
-
-      // For .. just move dirfd
-      if (len) {
-        // Not a symlink: add to linked list, move dirfd, fail if error
-        if ((exact || todo) && errno != EINVAL) goto error;
-        new->next = done;
-        done = new;
-        if (errno == EINVAL && !todo) break;
-        s = new->str;
+
+      new->next = done;
+      done = new;
+      if (errno == EINVAL && !todo) break;
+      if (errno == ENOENT && exact<0) {
+        missing++;
+        continue;
       }
-      fd = openat(dirfd, s, 0);
+      if (errno != EINVAL && (exact || todo)) goto error;
+
+      fd = openat(dirfd, new->str, 0);
       if (fd == -1 && (exact || todo || errno != ENOENT)) goto error;
       close(dirfd);
       dirfd = fd;
@@ -588,7 +597,7 @@ error:
   llist_traverse(todo, free);
   llist_traverse(done, free);
 
-  return NULL;
+  return 0;
 }
 
 void xchdir(char *path)
diff --git a/tests/readlink.test b/tests/readlink.test
index 48104e58..52121770 100755
--- a/tests/readlink.test
+++ b/tests/readlink.test
@@ -48,6 +48,9 @@ testing "-f link/missing" "readlink -f dir/boing" \
   "$APWD/sub/boing\n" "" ""
 testing "-f /dev/null/file" \
   "readlink -f /dev/null/file 2>/dev/null || echo yes" "yes\n" "" ""
+testing "-m missing/dir" "readlink -m sub/two/three" "$APWD/sub/two/three\n" "" ""
+testing "-m missing/../elsewhere" "readlink -m sub/two/../../three" "$APWD/three\n" "" ""
+testing "-m file/dir" "readlink -m sub/bang/two 2>/dev/null || echo err" "err\n" "" ""
 rm link
 ln -sf / link || exit 1
 testing "-f link->/" "readlink -e link/dev" "/dev\n" "" ""
diff --git a/toys/other/readlink.c b/toys/other/readlink.c
index fecd1ef8..2e0cf11e 100644
--- a/toys/other/readlink.c
+++ b/toys/other/readlink.c
@@ -2,7 +2,7 @@
  *
  * Copyright 2007 Rob Landley <rob@landley.net>
 
-USE_READLINK(NEWTOY(readlink, "<1>1fenq[-fe]", TOYFLAG_USR|TOYFLAG_BIN))
+USE_READLINK(NEWTOY(readlink, "<1>1nqmef[-mef]", TOYFLAG_USR|TOYFLAG_BIN))
 
 config READLINK
   bool "readlink"
@@ -16,6 +16,7 @@ config READLINK
 
     -e	cannonical path to existing entry (fail if missing)
     -f	full path (fail if directory missing)
+    -m	ignore missing entries, show where it would be
     -n	no trailing newline
     -q	quiet (no output, just error code)
 */
@@ -28,9 +29,9 @@ void readlink_main(void)
   char *s;
 
   // Calculating full cannonical path?
-
-  if (toys.optflags & (FLAG_f|FLAG_e))
-    s = xabspath(*toys.optargs, toys.optflags & FLAG_e);
+  // Take advantage of flag positions to calculate m = -1, f = 0, e = 1
+  if (toys.optflags & (FLAG_f|FLAG_e|FLAG_m))
+    s = xabspath(*toys.optargs, (toys.optflags&(FLAG_f|FLAG_e))-1);
   else s = xreadlink(*toys.optargs);
 
   if (s) {