dd: support iseek= and oseek=

Alias iseek=N to skip=N, oseek=N to seek=N (Bug#45648).
* src/dd.c (scanargs): Parse iseek= and oseek=.
* tests/dd/skip-seek.pl (sk-seek5): New test case.

NEWS

@@ -57,6 +57,9 @@ GNU coreutils NEWS                                    -*- outline -*-
   dd conv=fsync now synchronizes output even after a write error,
   and similarly for dd conv=fdatasync.
 
+  dd now supports the aliases iseek=N for skip=N, and oseek=N for seek=N,
+  like FreeBSD and other operating systems.
+
   timeout --foreground --kill-after=... will now exit with status 137
   if the kill signal was sent, which is consistent with the behavior
   when the --foreground option is not specified.  This allows users to

doc/coreutils.texi

@@ -9189,8 +9189,7 @@ Read from @var{file} instead of standard input.
 @item of=@var{file}
 @opindex of
 Write to @var{file} instead of standard output.  Unless
-@samp{conv=notrunc} is given, @command{dd} truncates @var{file} to zero
-bytes (or the size specified with @samp{seek=}).
+@samp{conv=notrunc} is given, truncate @var{file} before writing it.
 
 @item ibs=@var{bytes}
 @opindex ibs
@@ -9230,15 +9229,20 @@ When converting variable-length records to fixed-length ones
 use @var{bytes} as the fixed record length.
 
 @item skip=@var{n}
+@itemx iseek=@var{n}
 @opindex skip
+@opindex iseek
 Skip @var{n} @samp{ibs}-byte blocks in the input file before copying.
 If @samp{iflag=skip_bytes} is specified, @var{n} is interpreted
 as a byte count rather than a block count.
 
 @item seek=@var{n}
+@itemx oseek=@var{n}
 @opindex seek
-Skip @var{n} @samp{obs}-byte blocks in the output file before copying.
-if @samp{oflag=seek_bytes} is specified, @var{n} is interpreted
+@opindex oseek
+Skip @var{n} @samp{obs}-byte blocks in the output file before
+truncating or copying.
+If @samp{oflag=seek_bytes} is specified, @var{n} is interpreted
 as a byte count rather than a block count.
 
 @item count=@var{n}
@@ -9588,14 +9592,14 @@ This flag can be used only with @code{iflag}.
 
 @item skip_bytes
 @opindex skip_bytes
-Interpret the @samp{skip=} operand as a byte count,
+Interpret the @samp{skip=} or @samp{iseek=} operand as a byte count,
 rather than a block count, which allows specifying
 an offset that is not a multiple of the I/O block size.
 This flag can be used only with @code{iflag}.
 
 @item seek_bytes
 @opindex seek_bytes
-Interpret the @samp{seek=} operand as a byte count,
+Interpret the @samp{seek=} or @samp{oseek=} operand as a byte count,
 rather than a block count, which allows specifying
 an offset that is not a multiple of the I/O block size.
 This flag can be used only with @code{oflag}.

src/dd.c

@@ -562,8 +562,8 @@ Copy a file, converting and formatting according to the operands.\n\
   obs=BYTES       write BYTES bytes at a time (default: 512)\n\
   of=FILE         write to FILE instead of stdout\n\
   oflag=FLAGS     write as per the comma separated symbol list\n\
-  seek=N          skip N obs-sized blocks at start of output\n\
-  skip=N          skip N ibs-sized blocks at start of input\n\
+  seek=N          (or oseek=N) skip N obs-sized output blocks\n\
+  skip=N          (or iseek=N) skip N ibs-sized input blocks\n\
   status=LEVEL    The LEVEL of information to print to stderr;\n\
                   'none' suppresses everything but error messages,\n\
                   'noxfer' suppresses the final transfer statistics,\n\
@@ -1564,9 +1564,9 @@ scanargs (int argc, char *const *argv)
               n_max = MIN (SIZE_MAX, IDX_MAX);
               converted_idx = &conversion_blocksize;
             }
-          else if (operand_is (name, "skip"))
+          else if (operand_is (name, "skip") || operand_is (name, "iseek"))
             skip = n;
-          else if (operand_is (name, "seek"))
+          else if (operand_is (name + (*name == 'o'), "seek"))
             seek = n;
           else if (operand_is (name, "count"))
             count = n;

tests/dd/skip-seek.pl

@@ -68,6 +68,16 @@ my @Tests =
       {OUT=> "bc\n"},
       {ERR=> "3+0 records in\n3+0 records out\n"},
      ],
+     [
+      # Check that iseek and oseek aliases work too.
+      'sk-seek5',
+      qw (bs=1 iseek=1 oseek=2 conv=notrunc count=3 status=noxfer of=@AUX@ < ),
+      {IN=> '0123456789abcdef'},
+      {AUX=> 'zyxwvutsrqponmlkji'},
+      {OUT=> ''},
+      {ERR=> "3+0 records in\n3+0 records out\n"},
+      {CMP=> ['zy123utsrqponmlkji', {'@AUX@'=> undef}]},
+     ],
     );
 
 my $save_temps = $ENV{DEBUG};