Programming Forums > Script Programming > Bash / Shell Scripting

cfriend · Sep 18th, 2004, 9:52 AM

Hi

Is there any way with grep to show me only the last pattern that matches and not all ? For example for a file with

linux 56
slackware 32
debian 34
linux 2
redhat 9

and $> grep linux filename

show me only --> linux 2
and not

linux 56
linux 2

Thanks

Ashcroft · Sep 18th, 2004, 10:19 AM

Hmm, bit tricky - you could do it with awk (and maybe sed) - but I'm not sure how to do it with grep.

Here is a perl one liner that will do it though.

(Toggle Plain Text)

$ perl -ne 'next unless (/linux/); $v = $_; { END { print $v } }' foo.txt

If you really have to do it with just shell tools just use awk to do pretty much the same thing that perl one liner does, overwrite a variable with each line that matches the pattern and have an END statement print the variable.

erebus · Sep 18th, 2004, 8:33 PM

Nice oneliner, bro. Overkill, but very nice... I could crank out an awk version, but it would be too similiar to that one, and it just does the job well enough. If you want it to run a little bit faster, try this:

(Toggle Plain Text)

$ grep "linux" foo | tail -1

Ashcroft · Sep 19th, 2004, 5:54 AM

Doh! Yeah 'tail' is a much simpler and faster way to do it.

-but you can never have too much overkill

erebus · Sep 19th, 2004, 6:20 PM

I really thought the awk solution to this would look the same or atleast very similiar. Little did I know that because of the lack of $_ in awk, I had to do a little research. This is a little bit more light-weight than the perl version above, but since perl is the all-in-one swiss army chainsaw, they go hand-in-hand depending on what you do:

(Toggle Plain Text)

$ awk '/linux/ { last = $0 }; END { print last }'foo

Sep 18th, 2004, 10:19 AM	#2
Ashcroft Programmer Join Date: Sep 2004 Posts: 38 Rep Power: 0	Hmm, bit tricky - you could do it with awk (and maybe sed) - but I'm not sure how to do it with grep. Here is a perl one liner that will do it though. (Toggle Plain Text) $ perl -ne 'next unless (/linux/); $v = $_; { END { print $v } }' foo.txt $ perl -ne 'next unless (/linux/); $v = $_; { END { print $v } }' foo.txt If you really have to do it with just shell tools just use awk to do pretty much the same thing that perl one liner does, overwrite a variable with each line that matches the pattern and have an END statement print the variable.

Sep 18th, 2004, 8:33 PM	#3
erebus Programmer Join Date: Aug 2004 Location: /dev/null Posts: 65 Rep Power: 4	Nice oneliner, bro. Overkill, but very nice... I could crank out an awk version, but it would be too similiar to that one, and it just does the job well enough. If you want it to run a little bit faster, try this: (Toggle Plain Text) $ grep "linux" foo \| tail -1 $ grep "linux" foo \| tail -1 __________________ <span style='font-size:14pt;line-height:100%'><span style='color:red'>"Political power grows out of the barrel of a gun" - Mao Tse-Tung</span></span>

Sep 19th, 2004, 6:20 PM	#5
erebus Programmer Join Date: Aug 2004 Location: /dev/null Posts: 65 Rep Power: 4	I really thought the awk solution to this would look the same or atleast very similiar. Little did I know that because of the lack of $_ in awk, I had to do a little research. This is a little bit more light-weight than the perl version above, but since perl is the all-in-one swiss army chainsaw, they go hand-in-hand depending on what you do: (Toggle Plain Text) $ awk '/linux/ { last = $0 }; END { print last }'foo $ awk '/linux/ { last = $0 }; END { print last }'foo __________________ <span style='font-size:14pt;line-height:100%'><span style='color:red'>"Political power grows out of the barrel of a gun" - Mao Tse-Tung</span></span>

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Sep 18th, 2004, 9:52 AM	#1
cfriend Newbie Join Date: Jul 2004 Posts: 8 Rep Power: 0	Hi Is there any way with grep to show me only the last pattern that matches and not all ? For example for a file with linux 56 slackware 32 debian 34 linux 2 redhat 9 and $> grep linux filename show me only --> linux 2 and not linux 56 linux 2 Thanks

Sep 19th, 2004, 5:54 AM	#4
Ashcroft Programmer Join Date: Sep 2004 Posts: 38 Rep Power: 0	Doh! Yeah 'tail' is a much simpler and faster way to do it. -but you can never have too much overkill

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Programming Forums > Script Programming > Bash / Shell Scripting

Grep Last Pattern Output