(S_TYPEISSHM): New macro.

(main): Report failed fstat.
Complain only when ftruncate fails on a regular file,
a directory, or a shared memory object.

diff --git a/src/dd.c b/src/dd.c
index 259bfa2..01447e5 100644 (file)
--- a/src/dd.c
+++ b/src/dd.c
@@ -48,6 +48,10 @@
 # define SIGINFO SIGUSR1
 #endif
 
+#ifndef S_TYPEISSHM
+# define S_TYPEISSHM(Mode) 0
+#endif
+
 #define ROUND_UP_OFFSET(X, M) ((M) - 1 - (((X) + (M) - 1) % (M)))
 #define PTR_ALIGN(Ptr, M) ((Ptr) \
                           + ROUND_UP_OFFSET ((char *)(Ptr) - (char *)0, (M)))
@@ -1260,11 +1264,18 @@ main (int argc, char **argv)
              o = seek_bytes;
            }
 
-         /* Attempt to use ftruncate only if STDOUT refers to a regular file.
-            On Linux 2.4.0, ftruncate fails with for non-regular files.  */
-         if (fstat (STDOUT_FILENO, &stdout_stat) == 0
-             && S_ISREG (stdout_stat.st_mode)
-             && ftruncate (STDOUT_FILENO, o) < 0)
+         if (fstat (STDOUT_FILENO, &stdout_stat) != 0)
+           error (1, errno, _("cannot fstat %s"), quote (output_file));
+
+         /* Complain only when ftruncate fails on a regular file, a
+            directory, or a shared memory object, as the 2000-08
+            POSIX draft specifies ftruncate's behavior only for these
+            file types.  For example, do not complain when Linux 2.4
+            ftruncate fails on /dev/fd0.  */
+         if (ftruncate (STDOUT_FILENO, o) != 0
+             && (S_ISREG (stdout_stat.st_mode)
+                 || S_ISDIR (stdout_stat.st_mode)
+                 || S_TYPEISSHM (stdout_stat.st_mode)))
            {
              char buf[LONGEST_HUMAN_READABLE + 1];
              if (seek_record)