hardlink: add --list-duplicates and --zero

--list-duplicates codifies what everyone keeps re-implementing with
find -exec b2sum or src:perforate's finddup or whatever.

hardlink already knows this, so make the data available thusly,
in a format well-suited for pipeline processing
(fixed-width key for uniq/cut/&c.,
 tab delimiter for cut &a.,
 -z for correct filename handling).

diff --git a/misc-utils/hardlink.1.adoc b/misc-utils/hardlink.1.adoc
index b6f07ba706cdf775d52d116d4c8600a6b9e7abe8..b85ba09d434cfae58dc0cfba257f67414cc5d2d7 100644 (file)
--- a/misc-utils/hardlink.1.adoc
+++ b/misc-utils/hardlink.1.adoc
@@ -76,6 +76,12 @@ Among equal files, keep the file with the lowest link count.
 *-n*, *--dry-run*::
 Do not act, just print what would happen.
 
+*-l*, *--list-duplicates*::
+Don't link anything, but list the absolute path of every duplicate file, one per line, preceded by a unique 16-byte discriminator and a tab.
+
+*-z*, *--zero*::
+Separate lines with a NUL instead of a newline in *-l* mode.
+
 *-o*, *--ignore-owner*::
 Link and compare files even if their owner information (user and group) differs. Results may be unpredictable.
 

diff --git a/misc-utils/hardlink.c b/misc-utils/hardlink.c
index e4b44c6c6d504000b6d4f1cea20f1634bb63b052..643df7cf24b5852cf362f0ef9d74275c9e528745 100644 (file)
--- a/misc-utils/hardlink.c
+++ b/misc-utils/hardlink.c
@@ -189,6 +189,8 @@ static struct options {
        unsigned int keep_oldest:1;
        unsigned int prio_trees:1;
        unsigned int dry_run:1;
+       unsigned int list_duplicates:1;
+       char line_delim;
        uintmax_t min_size;
        uintmax_t max_size;
        size_t io_size;
@@ -206,6 +208,7 @@ static struct options {
        .respect_xattrs = FALSE,
        .keep_oldest = FALSE,
        .prio_trees = FALSE,
+       .line_delim = '\n',
        .min_size = 1,
        .cache_size = 10*1024*1024
 };
@@ -1152,6 +1155,10 @@ static void visitor(const void *nodep, const VISIT which, const int depth)
 
        /* final cleanup */
        for (other = begin; other != NULL; other = other->next) {
+               if (opts.list_duplicates && other->st.st_nlink > 1)
+                       for (struct link *l = other->links; l; l = l->next)
+                               printf("%016zu\t%s%c", (size_t)other, l->path, opts.line_delim);
+
                if (ul_fileeq_data_associated(&other->data))
                        ul_fileeq_data_deinit(&other->data);
        }
@@ -1182,6 +1189,8 @@ static void __attribute__((__noreturn__)) usage(void)
                "                              lowest hardlink count\n"), out);
        fputs(_(" -M, --minimize             reverse the meaning of -m\n"), out);
        fputs(_(" -n, --dry-run              don't actually link anything\n"), out);
+       fputs(_(" -l, --list-duplicates      print every group of duplicate files\n"), out);
+       fputs(_(" -z, --zero                 delimit output with NULs instead of newlines\n"), out);
        fputs(_(" -o, --ignore-owner         ignore owner changes\n"), out);
        fputs(_(" -F, --prioritize-trees     files found in the earliest specified top-level\n"
                 "                              directory have higher priority (lower precedence\n"
@@ -1223,7 +1232,7 @@ static int parse_options(int argc, char *argv[])
                OPT_REFLINK = CHAR_MAX + 1,
                OPT_SKIP_RELINKS
        };
-       static const char optstr[] = "VhvndfpotXcmMFOx:y:i:r:S:s:b:q";
+       static const char optstr[] = "VhvndfpotXcmMFOlzx:y:i:r:S:s:b:q";
        static const struct option long_options[] = {
                {"version", no_argument, NULL, 'V'},
                {"help", no_argument, NULL, 'h'},
@@ -1252,6 +1261,8 @@ static int parse_options(int argc, char *argv[])
                {"content", no_argument, NULL, 'c'},
                {"quiet", no_argument, NULL, 'q'},
                {"cache-size", required_argument, NULL, 'r'},
+               {"list-duplicates", no_argument, NULL, 'l'},
+               {"zero", no_argument, NULL, 'z'},
                {NULL, 0, NULL, 0}
        };
        static const ul_excl_t excl[] = {
@@ -1329,6 +1340,14 @@ static int parse_options(int argc, char *argv[])
                case 'b':
                        opts.io_size = strtosize_or_err(optarg, _("failed to parse I/O size"));
                        break;
+               case 'l':
+                       opts.list_duplicates = TRUE;
+                       opts.dry_run = TRUE;
+                       quiet = TRUE;
+                       break;
+               case 'z':
+                       opts.line_delim = '\0';
+                       break;
 #ifdef USE_REFLINK
                case OPT_REFLINK:
                        reflink_mode = REFLINK_AUTO;