On 08/06/2010 00:59, Brian Somers wrote:
On Mon, 07 Jun 2010 13:05:48 +0200, Dag-Erling Smørgrav d...@des.no wrote:
Bakul Shah ba...@bitblocks.com writes:
Except read doesn't do it quite right:
$ ps | (read a; echo $a ; grep zsh)
PID TT STAT TIME COMMAND
yeah, I forgot that it drops
Bakul Shah ba...@bitblocks.com writes:
Except read doesn't do it quite right:
$ ps | (read a; echo $a ; grep zsh)
PID TT STAT TIME COMMAND
yeah, I forgot that it drops leading whitespace...
DES
--
Dag-Erling Smørgrav - d...@des.no
___
On Mon, 07 Jun 2010 13:05:48 +0200, Dag-Erling Smørgrav d...@des.no wrote:
Bakul Shah ba...@bitblocks.com writes:
Except read doesn't do it quite right:
$ ps | (read a; echo $a ; grep zsh)
PID TT STAT TIME COMMAND
yeah, I forgot that it drops leading whitespace...
Well, leading
Doug Barton do...@freebsd.org writes:
Bakul Shah ba...@bitblocks.com writes:
$ ps|(head -1; grep sh)
PID TT STAT TIME COMMAND
I don't understand why you think this would work. There is no input to
the grep command. The only reason it exits at all is that you are
executing in a
On 06/06/10 07:33, Dag-Erling Smørgrav wrote:
Doug Bartondo...@freebsd.org writes:
Bakul Shahba...@bitblocks.com writes:
$ ps|(head -1; grep sh)
PID TT STAT TIME COMMAND
I don't understand why you think this would work. There is no input to
the grep command. The only reason it
Doug Barton do...@freebsd.org writes:
If you have a 2 line file named foo that looks like this:
one
two
Then do: cat foo | (cat ; echo 'blah' ; cat)
you get:
one
two
blah
prompt
which seems to indicate to me that unless the first command is a shell
builtin that the first command is
On 06/06/10 15:13, Dag-Erling Smørgrav wrote:
The second command will receive whatever is left after the first is
done. Otherwise, read(1) loops wouldn't work. You chose a poor
example, since cat(1) consumes*everything*.
Fair enough. My point remains though, using this technique is liable to
On Mon, 07 Jun 2010 00:13:28 +0200 =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?=
d...@des.no wrote:
The reason why head(1) doesn't work as expected is that it uses buffered
I/O with a fairly large buffer, so it consumes more than it needs. The
only way to make it behave as the OP expected is to use
Bakul Shah ba...@bitblocks.com wrote:
+--
| [cc'ed Rob in case he wishes to chime in]
+-
No, I think you covered most of it quite well [including the bit
about grep -m not working properly in the case of pipes, sockets,
special files, etc.], thanks.
Yes, I know that grep(1) only
Consider:
$ yes | cat -n | (read a; echo $a; head -1)
1 y
2 y
$ yes | cat -n | (head -1; read a; echo $a)
1 y
456 y
As you can see, head reads far more than it should. This is
fine most of the time but often it results in surprising
output:
# print ps header and all
On 06/05/10 13:12, Bakul Shah wrote:
Consider:
$ yes | cat -n | (read a; echo $a; head -1)
1 y
2 y
$ yes | cat -n | (head -1; read a; echo $a)
1 y
456 y
It's not at all clear to me what you are trying to accomplish here. If
what you want is to read only the first line
On Sat, 05 Jun 2010 13:32:08 PDT Doug Barton do...@freebsd.org wrote:
On 06/05/10 13:12, Bakul Shah wrote:
Consider:
$ yes | cat -n | (read a; echo $a; head -1)
1 y
2 y
$ yes | cat -n | (head -1; read a; echo $a)
1 y
456 y
It's not at all clear to me
On 06/05/10 13:48, Bakul Shah wrote:
Without running the following can you guess its output?
$ look '' | (head -2; head -2)
Again, it's not clear to me what you expect is going to happen with the
second 'head -2' there. I agree that the actual output of your example
is wacky and unexpected,
it needs to].
It would be less surprising and more useful if
$ ps | (head -1; grep ssh)
showed
PID TT STAT TIME COMMAND
all line with ssh in it
The change in head behaviour I am suggesting wouldn't break
anything that already works but make it more useful for what
you call
On Sat, 05 Jun 2010 17:02:42 EDT Mike Meyer m...@mired.org wrote:
As a general rule, programs don't expect to share their input with
other programs, nor do they make guarantees about what is and isn't
read from that input under those conditions. I'd say that shell
scripts that depend on what
On 05/06/2010 23:37, Bakul Shah wrote:
On Sat, 05 Jun 2010 14:02:16 PDT Doug Barton do...@freebsd.org wrote:
It would be less surprising and more useful if
$ ps | (head -1; grep ssh)
showed
PID TT STAT TIME COMMAND
all line with ssh in it
The change in head
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