losetup: with no arguments lists all /dev/loopN. Corrected help text.

(patch by Vladimir Dronnikov <dronnikov@gmail.ru>)

2 files changed, 18 insertions, 5 deletions

diff --git a/include/usage.h b/include/usage.h
index 8b8d64e84..36739c712 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -1623,13 +1623,14 @@ USE_FEATURE_DATE_ISOFMT( \
         "\t-f\t\toutput data as the log grows"
 
 #define losetup_trivial_usage \
-        "[-od] LOOPDEVICE [FILE]"
+        "[-o OFFSET] [-d] LOOPDEVICE [FILE]]"
 #define losetup_full_usage \
-        "Associate LOOPDEVICE with FILE, or display current association.\n\n" \
+        "(Dis)associate LOOPDEVICE with FILE, or display current associations.\n\n" \
         "Options:\n" \
         "\t-d\t\tDisassociate LOOPDEVICE\n" \
         "\t-o OFFSET\tStart OFFSET bytes into FILE"
 #define losetup_notes_usage \
+        "No arguments will display all current associations.\n" \
         "One argument (losetup /dev/loop1) will display the current association\n" \
         "(if any), or disassociate it (with -d).  The display shows the offset\n" \
         "and filename of the file the loop device is currently bound to.\n\n" \
diff --git a/util-linux/losetup.c b/util-linux/losetup.c
index af0b03a53..6b9a810f2 100644
--- a/util-linux/losetup.c
+++ b/util-linux/losetup.c
@@ -22,7 +22,8 @@ int losetup_main(int argc, char **argv)
         argc -= optind;
         argv += optind;
 
-        if (opt == 0x3) bb_show_usage(); // -d and -o (illegal)
+        if (opt == 0x3) // -d + -o (illegal)
+                bb_show_usage();
 
         if (opt == 0x1) { // -d
                 /* detach takes exactly one argument */
@@ -46,7 +47,18 @@ int losetup_main(int argc, char **argv)
                 if (!s) bb_perror_nomsg_and_die();
                 printf("%s: %s\n", argv[0], s);
                 if (ENABLE_FEATURE_CLEAN_UP) free(s);
-        } else
-                bb_show_usage();
+        } else {
+                char dev[11] = "/dev/loop0";
+                char c;
+                for (c = '0'; c <= '9'; ++c) {
+                        char *s;
+                        dev[9] = c;
+                        s = query_loop(dev);
+                        if (s) {
+                                printf("%s: %s\n", dev, s);
+                                if (ENABLE_FEATURE_CLEAN_UP) free(s);
+                        }
+                }
+        }
         return EXIT_SUCCESS;
 }