dd now truncates files at the end its write, this can be turned of by

specifying conv=notrunc in the command line

This conforms to GNU dd behaviour

1 files changed, 10 insertions, 3 deletions

diff --git a/dd.c b/dd.c
index 84f3211fb..5ab0a90af 100644
--- a/dd.c
+++ b/dd.c
@@ -48,6 +48,7 @@ extern int dd_main(int argc, char **argv)
         int outFd;
         int inCc = 0;
         int outCc;
+        int trunc=TRUE;
         long blockSize = 512;
         uintmax_t skipBlocks = 0;
         uintmax_t seekBlocks = 0;
@@ -57,6 +58,7 @@ extern int dd_main(int argc, char **argv)
         uintmax_t totalSize;
         uintmax_t readSize;
         unsigned char buf[BUFSIZ];
+        char *keyword = NULL;
 
         argc--;
         argv++;
@@ -69,7 +71,7 @@ extern int dd_main(int argc, char **argv)
                         outFile = ((strchr(*argv, '=')) + 1);
                 else if (strncmp("count", *argv, 5) == 0) {
                         count = getNum((strchr(*argv, '=')) + 1);
-                        if (count <= 0) {
+                        if (count < 0) {
                                 errorMsg("Bad count value %s\n", *argv);
                                 goto usage;
                         }
@@ -92,7 +94,10 @@ extern int dd_main(int argc, char **argv)
                                 errorMsg("Bad seek value %s\n", *argv);
                                 goto usage;
                         }
-
+                } else if (strncmp(*argv, "conv", 4) == 0) {
+                        keyword = (strchr(*argv, '=') + 1);
+                        if (strcmp(keyword, "notrunc") == 0) 
+                                trunc=FALSE;
                 } else {
                         goto usage;
                 }
@@ -141,7 +146,9 @@ extern int dd_main(int argc, char **argv)
                         break;
                 outTotal += outCc;
         }
-
+        if (trunc == TRUE) {
+                ftruncate(outFd, lseek(outFd, 0, SEEK_CUR));
+        }
         /* Note that we are not freeing memory or closing
          * files here, to save a few bytes. */
 #ifdef BB_FEATURE_CLEAN_UP