Re: gzip: gzip -cf refusing to compress devices

[Paul Eggert]

Thanks for reporting that problem.  The full fix is a bit trickier
than I'd like, but I've installed the following into the gzip CVS
sources.

2006-12-23  Paul Eggert  <address@hidden>

        * NEWS: Fix bug reported by Martin Mares in
        <http://bugs.debian.org/177942>.
        * gzip.c (treat_stdin): Remove NO_STDIN_FSTAT and NO_PIPE_TIMESTAMP
        stuff.  It didn't work (led to syntax errors) and was confusing.
        Report an error if stdin cannot be statted even if !list && no_time.
        Get stdin's size if it is regular.
        (treat_file): Do not report an error with setuid, setgid,
        sticky, or non-regular, non-directory files if to_stdout.
        Allow 'force' to override the caution about sticky files.
        Use the same form for time stamps that treat_stdin uses.

--- NEWS        24 Dec 2006 05:25:19 -0000      1.11
+++ NEWS        24 Dec 2006 05:45:05 -0000
@@ -2,6 +2,9 @@ Gzip 1.3.10 (200?-??-??)

 * zcmp and zdiff did not work in the usual case, due to a typo.

+* gzip -c and zcat now work on special files, files with special mode bits,
+  and files with multiple hard links.
+
 Gzip 1.3.9 (2006-12-15)

 * No major changes; only porting fixes.
--- gzip.c      12 Dec 2006 00:03:17 -0000      1.11
+++ gzip.c      24 Dec 2006 05:45:05 -0000
@@ -616,22 +616,16 @@ local void treat_stdin()
     strcpy(ifname, "stdin");
     strcpy(ofname, "stdout");

-    /* Get the time stamp on the input file. */
-    time_stamp.tv_nsec = -1;  /* The time is unknown by default.  */
-
-#ifndef NO_STDIN_FSTAT
-    if (list || !no_time) {
-       if (fstat(fileno(stdin), &istat) != 0) {
-           progerror("standard input");
-           do_exit(ERROR);
-       }
-# ifdef NO_PIPE_TIMESTAMP
-       if (S_ISREG(istat.st_mode))
-# endif
-           time_stamp = get_stat_mtime (&istat);
-#endif /* NO_STDIN_FSTAT */
-    }
-    ifile_size = -1L; /* convention for unknown size */
+    /* Get the file's time stamp and size.  */
+    if (fstat (fileno (stdin), &istat) != 0)
+      {
+       progerror ("standard input");
+       do_exit (ERROR);
+      }
+    ifile_size = S_ISREG (istat.st_mode) ? istat.st_size : -1;
+    time_stamp.tv_nsec = -1;
+    if (!no_time || list)
+      time_stamp = get_stat_mtime (&istat);

     clear_bufs(); /* clear input and output buffers */
     to_stdout = 1;
@@ -710,48 +704,57 @@ local void treat_file(iname)
               program_name, ifname));
        return;
     }
-    if (!S_ISREG(istat.st_mode)) {
-       WARN((stderr,
-             "%s: %s is not a directory or a regular file - ignored\n",
-             program_name, ifname));
-       close (ifd);
-       return;
-    }

-    if (istat.st_mode & S_ISUID)
+    if (! to_stdout)
       {
-       WARN ((stderr, "%s: %s is set-user-ID on execution - ignored\n",
-              program_name, ifname));
-       close (ifd);
-       return;
-      }
-    if (istat.st_mode & S_ISGID)
-      {
-       WARN ((stderr, "%s: %s is set-group-ID on execution - ignored\n",
-              program_name, ifname));
-       close (ifd);
-       return;
-      }
-    if (istat.st_mode & S_ISVTX)
-      {
-       WARN ((stderr, "%s: %s has the sticky bit set - file ignored\n",
-              program_name, ifname));
-       close (ifd);
-       return;
-      }
+       if (! S_ISREG (istat.st_mode))
+         {
+           WARN ((stderr,
+                  "%s: %s is not a directory or a regular file - ignored\n",
+                  program_name, ifname));
+           close (ifd);
+           return;
+         }
+       if (istat.st_mode & S_ISUID)
+         {
+           WARN ((stderr, "%s: %s is set-user-ID on execution - ignored\n",
+                  program_name, ifname));
+           close (ifd);
+           return;
+         }
+       if (istat.st_mode & S_ISGID)
+         {
+           WARN ((stderr, "%s: %s is set-group-ID on execution - ignored\n",
+                  program_name, ifname));
+           close (ifd);
+           return;
+         }

-    if (istat.st_nlink > 1 && !to_stdout && !force) {
-       WARN((stderr, "%s: %s has %lu other link%c -- unchanged\n",
-             program_name, ifname, (unsigned long) istat.st_nlink - 1,
-             istat.st_nlink > 2 ? 's' : ' '));
-       close (ifd);
-       return;
-    }
+       if (! force)
+         {
+           if (istat.st_mode & S_ISVTX)
+             {
+               WARN ((stderr,
+                      "%s: %s has the sticky bit set - file ignored\n",
+                      program_name, ifname));
+               close (ifd);
+               return;
+             }
+           if (2 <= istat.st_nlink)
+             {
+               WARN ((stderr, "%s: %s has %lu other link%c -- unchanged\n",
+                      program_name, ifname,
+                      (unsigned long int) istat.st_nlink - 1,
+                      istat.st_nlink == 2 ? ' ' : 's'));
+               close (ifd);
+               return;
+             }
+         }
+      }

-    ifile_size = istat.st_size;
-    if (no_time && !list)
-      time_stamp.tv_nsec = -1;
-    else
+    ifile_size = S_ISREG (istat.st_mode) ? istat.st_size : -1;
+    time_stamp.tv_nsec = -1;
+    if (!no_time || list)
       time_stamp = get_stat_mtime (&istat);

     /* Generate output file name. For -r and (-t or -l), skip files