Re: [coreutils] [PATCH] head: optionally indicate underrun of set limit
On 24/11/10 16:34, Pádraig Brady wrote:
On 23/11/10 16:34, Pádraig Brady wrote:
On 23/11/10 16:24, Stefan Tomanek wrote:
Dies schrieb Stefan Tomanek (stefan.toma...@wertarbyte.de):
It is often convinient to detect whether head has in fact printed the
requested number of lines or if EOF was reached before reaching that
point. This patch adds the option --indicate-underrun, which makes
head exit with a status of 4 instead of 0 if no more data could be
read from its input.
Any thoughts about this change? It's a rather small patch, but would
be quite useful (at least for me).
Note the above use case is now supported with `split --filter`
http://git.sv.gnu.org/gitweb/?p=coreutils.git;a=commit;h=a09d9e5b
(Note currently the number of chunks is limited by --suffix-length).
The following addresses both issues and
also uses existing coreutils functionality:
process_part() { echo processing $(wc -c) bytes; }
while true; do
c=$(od -tx1 -An -N1)
test $c || break
c=$(echo $c) #strip leading ' '
{ printf \x$c; head -c9; } | process_part
done
BTW I previously created a script with the above,
since it seems so useful. So you can use this for older systems:
https://github.com/pixelb/scripts/commits/master/scripts/split_to
cheers,
Pádraig.
Re: [coreutils] [PATCH] head: optionally indicate underrun of set limit
On 23/11/10 16:34, Pádraig Brady wrote:
On 23/11/10 16:24, Stefan Tomanek wrote:
Dies schrieb Stefan Tomanek (stefan.toma...@wertarbyte.de):
It is often convinient to detect whether head has in fact printed the
requested number of lines or if EOF was reached before reaching that
point. This patch adds the option --indicate-underrun, which makes
head exit with a status of 4 instead of 0 if no more data could be
read from its input.
Any thoughts about this change? It's a rather small patch, but would
be quite useful (at least for me).
This does seem useful on the face of it.
I need to do a little further investigation
to see if there are existing ways to achieve the same.
I was wondering about the logic in your example BTW.
If there is no input then you'll process an empty chunk
or if the input is an exact multiple of the chunk size
you'll process an empty chunk at the end.
The following addresses both issues and
also uses existing coreutils functionality:
process_part() { echo processing $(wc -c) bytes; }
while true; do
c=$(od -tx1 -An -N1)
test $c || break
c=$(echo $c) #strip leading ' '
{ printf \x$c; head -c9; } | process_part
done
cheers,
Pádraig.
p.s. \x is not a printf standard so the
script probably needs tweaking for dash
p.p.s. I noticed the related ifne util from moreutils
