On Wed, Jul 15, 2009 at 11:51:41PM +0200, Jim Meyering wrote:
> If it matters, we can come up with a more efficient (yet still portable)
> way to compare the last two bytes of each file to "\n\n".
> I went ahead and wrote a nearly-minimal script to do that.
> Rather than reading/processing all 27MB of sources,
> this reads just the last 2 bytes of each of the 1048 files,
> comparing those bytes to "\n\n" and printing the name when
> there's a match:
I just strace'd the 'tail' program and that does the right
thing too
# strace tail -c 2 somefile
....
open("somefile", O_RDONLY|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFREG|0664, st_size=10600, ...}) = 0
_llseek(3, 0, [0], SEEK_CUR) = 0
_llseek(3, 0, [10600], SEEK_END) = 0
_llseek(3, -2, [10598], SEEK_END) = 0
read(3, "l\n"..., 2) = 2
> git ls-files -z \
> | xargs -0 perl -le '
> foreach my $f (@ARGV) {
> open F,"<",$f or (warn "failed to open $f: $!\n"), next;
> my $p = sysseek(F, -2, 2);
> # seek failure probably means file has < 2 bytes; ignore
> my $two;
> defined $p and $p = sysread F,$two,2;
> close F;
> # ignore read failure
> $p && $two eq "\n\n" and (print $f),$fail=1;
> } END {exit defined $fail ? 1 : 0}'
So using 'tail' instead of this perl script would be more readable
and efficient.
Daniel
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