dd: add count_bytes, skip_bytes and seek_bytes flags

dd now accepts the count_bytes and skip_bytes input flag and the
seek_bytes output flag, to more easily allow processing portions of a
file.

* src/dd.c (scanargs): Compute skip_records and skip_bytes when
'skip_bytes' iflag is used. Compute max_records and max_bytes when
'count_bytes' iflag is used. Compute seek_records and seek_bytes
when 'seek_bytes' oflag is used.
(skip_via_lseek): Use new 'bytes' parameter and handle potential
'records' equals to zero. Update the bytes parameter when called with
'fdesc' equal to STDOUT_FILENO. Update the header comments.
(dd_copy): Skip accordingly to skip_records AND skip_bytes. Count
accordingly to max_records AND max_bytes. Seek on output accordingly
to seek_records AND seek_bytes.
* NEWS (New features): Mention it.
* doc/coreutils.texi (dd invocation): Detail new flags and behaviors.
* tests/dd/bytes: New file. Tests for these new flags.
* tests/Makefile.am (TESTS): Add it.

2 files changed, 58 insertions, 0 deletions

diff --git a/tests/Makefile.am b/tests/Makefile.am
index c951f69a1..7b5368195 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -369,6 +369,7 @@ TESTS =						\
   dd/reblock					\
   dd/skip-seek					\
   dd/skip-seek2					\
+  dd/bytes					\
   dd/skip-seek-past-file			\
   dd/stderr					\
   dd/unblock					\
diff --git a/tests/dd/bytes b/tests/dd/bytes
new file mode 100755
index 000000000..603874290
--- /dev/null
+++ b/tests/dd/bytes
@@ -0,0 +1,57 @@
+#!/bin/sh
+
+# Copyright (C) 2012 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+print_ver_ dd
+
+# count_bytes
+echo 0123456789abcdefghijklm > in || framework_failure_
+dd count=14 conv=swab iflag=count_bytes < in > out 2> /dev/null || fail=1
+case `cat out` in
+ 1032547698badc) ;;
+ *) fail=1 ;;
+esac
+
+# skip_bytes
+echo 0123456789abcdefghijklm > in || framework_failure_
+dd skip=10 iflag=skip_bytes < in > out 2> /dev/null || fail=1
+case `cat out` in
+ abcdefghijklm) ;;
+ *) fail=1 ;;
+esac
+
+# skip records and bytes from pipe
+echo 0123456789abcdefghijklm |
+ dd skip=10 bs=2 iflag=skip_bytes > out 2> /dev/null || fail=1
+case `cat out` in
+ abcdefghijklm) ;;
+ *) fail=1 ;;
+esac
+
+# seek bytes
+echo abcdefghijklm |
+ dd bs=5 seek=8 oflag=seek_bytes > out 2> /dev/null || fail=1
+echo abcdefghijklm |
+ dd bs=4 seek=2 > expected 2> /dev/null || fail=1
+compare expected out || fail=1
+
+# seek bytes on empty file
+echo abcdefghijklm |
+ dd bs=5 seek=8 oflag=seek_bytes > out2 2> /dev/null || fail=1
+compare expected out2 || fail=1
+
+Exit $fail