Re: Awk, filtering match through external command
Provided you can rely on gawk extensions, a coprocess [1] should help. [1] https://www.gnu.org/software/gawk/manual/gawk.html#Getline_002fCoprocess -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20121228161728.6e6c1611@debws
Re: Awk, filtering match through external command
Neal Murphy neal.p.mur...@alum.wpi.edu wrote: I don't see a way to pipe both ends of an external command. I'm not sure even *perl* could do that. It can [*], see IPC::Open2 and IPC::Open3. But you can end up with all sorts of buffer related race conditions. Chris -- [*] are you really surprised? -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/gfbvn9xn65@news.roaima.co.uk
Re: Awk, filtering match through external command
T o n g wrote:
...
Any way to filter through external command to variable, somewhat like:
head /etc/group | awk '{print $0 | cut -d':' -f1 | getline result ;}'
looks like you want to assign the output of command to
a variable.
in shell or bash use the backquote character `
result=`head /etc/group | cut -d: -f1`
example run:
me@ant(16)~$ result=`head /etc/group | cut -d: -f1`
me@ant(17)~$ echo $result
root daemon bin sys adm tty disk lp mail news
songbird
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Re: Awk, filtering match through external command
On Sat, 10 Nov 2012 00:36:48 -0500, John L. Cunningham wrote:
Well...
head /etc/group |\
awk '{echo $0 | cut -d: -f1 | getline result; print result}'
...seems to work.
Great. Thanks.
But it is also very silly.
Again, as I said, this is only
*for the sake of illustration of filtering through external command*.
I didn't want to complicate/distract the discussion on how to match a
piece of segment on a complicated XML string then beautify it via
external command tidy, then do further processing..., all within awk,
make sense now?
Thanks everyone!
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Re: Awk, filtering match through external command
On Thu, 08 Nov 2012 23:29:23 -0500, John L. Cunningham wrote:
However, I want the cmd itself a piping command as well. E.g..,
echo substr($0, RSTART, RLENGTH) | command external with
parameters|
getline result
I'm not getting it. Perhaps you could post a sample input with the
desired output?
*For the sake of illustration of filtering through external command*:
It's OK to:
head /etc/group | awk '{print $0 | cut -d':' -f1;}'
or,
head /etc/group | awk '{ echo $0 | getline result ; print result}'
Any way to filter through external command to variable, somewhat like:
head /etc/group | awk '{print $0 | cut -d':' -f1 | getline result ;}'
Any way to make it works?
Thanks
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Re: Awk, filtering match through external command
On Sat, Nov 10, 2012 at 04:28:29AM +, T o n g wrote:
It's OK to:
head /etc/group | awk '{print $0 | cut -d':' -f1;}'
Why not:
head /etc/group | awk -F: '{print $1}'
or,
head /etc/group | awk '{ echo $0 | getline result ; print result}'
Any way to filter through external command to variable, somewhat like:
head /etc/group | awk '{print $0 | cut -d':' -f1 | getline result ;}'
Any way to make it works?
Well...
head /etc/group |\
awk '{echo $0 | cut -d: -f1 | getline result; print result}'
...seems to work. But it is also very silly.
--
John
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Re: Awk, filtering match through external command
On Friday, November 09, 2012 11:28:29 PM T o n g wrote:
Any way to filter through external command to variable, somewhat like:
head /etc/group | awk '{print $0 | cut -d':' -f1 | getline result ;}'
Any way to make it works?
You'd *think* there'd be a way to do that, but I don't think awk works that
way. I don't see a way to pipe both ends of an external command. I'm not sure
even *perl* could do that.
Your best bet is to follow the ancient UNIX mantra of writing a program or
script to do one thing well. Split the awk script into two parts, as in:
awk -f part1 file | external_filter | awk -f part2
Of course, if it's a simple filter like the one you illustrated, you can do it
in awk:
awk '{split($0, result, :); print result[1];}' /etc/group
or
awk '{sub(/:.*/, , $0); print;}' /etc/group
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Re: Awk, filtering match through external command
On Fri, Nov 09, 2012 at 03:47:15AM +, T o n g wrote: Hi, Awk allows reading results from external command: cmd | getline result Over in comp.lang.awk they will tell you to avoid using getline if at all possible because it changes the way your program operates in ways that are difficult to anticipate. However, I want the cmd itself a piping command as well. E.g.., echo substr($0, RSTART, RLENGTH) | command external with parameters| getline result Any way to make it works? I'm not getting it. Perhaps you could post a sample input with the desired output? -- John -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20121109042922.ga10...@cerulean.myhome.westell.com
