Unix Bash shell command to grep some text if another grep matches

Question

I have an XML file in unix directory. I would like to search for some character if that is present, then grep the text located 3 lines before this matched line,.

Here is My File: (abc.xml)

<task Col="5" Object="BCD">
<checkpoint TcpOn="0"/>
<after ActFlg="0"/>
</task>
<task Col="6" Object="ABCD">
<checkpoint TcpOn="0"/>
<after ActFlg="1"/>
</task>
<task Col="7" Object="ABCDE">
<checkpoint TcpOn="0"/>
<after ActFlg="1"/>
</task>

Unix Code:

grep -i 'actflg="1"' abc.xml

Current Answer: This is returning the line where it is located.

<after ActFlg="1"/>
<after ActFlg="1"/>

What i Want is : (i want to do a further grep to display output as follows if actflg="1" is found...)

<task Col="6" Object="ABCD">
<task Col="7" Object="ABCDE">

@devnull : No, it can any file.. this scenario is for xml file.. I have other files as well.. — logan
– logan, Commented Feb 7, 2014 at 13:56
@devnull : This is not duplicate.. This is not working, if the same actflg="1" repeats multiple time — logan
– logan, Commented Feb 7, 2014 at 14:02

fedorqui · Accepted Answer · 2014-02-07 15:00:21Z

3

You can use grep -B XX, which print XX lines before matching lines. Then you use head -1 to just print the first one:

$ grep -B2 -i 'actflg="1"' file
<task Col="6" Object="ABCD">
<checkpoint TcpOn="0"/>
<after ActFlg="1"/>

$ grep -B2 -i 'actflg="1"' file | head -1
<task Col="6" Object="ABCD">

In case there are multiple matches, you can do:

$ awk '/ActFlg="1"/ {print preprev} {preprev=prev; prev=$0}' file
<task Col="6" Object="ABCD">
<task Col="7" Object="ABCDE">

Explanation

'/ActFlg="1"/ {print preprev} matches lines containing ActFlg="1" and does print preprev, a stored line.
{preprev=prev; prev=$0} this keeps storing the two previous lines. The 2 before is stored in preprev and the previous in prev. So whenever we are in a new line, this gets updated.

edited Feb 7, 2014 at 15:00

answered Feb 7, 2014 at 13:55

fedorqui

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9 Comments

logan Over a year ago

This is not showing , if the same actflg="1" repeats multiple time

fedorqui Over a year ago

Well I replied based on your sample input. If you change the sample, don't come and downvote...

logan Over a year ago

I did not do that !! Please remember that i am here to ask for help ! anyone's answer is well appreciated even if it is wrong because they help me !!

fedorqui Over a year ago

OK I thought it was your downvote. It is a bit tricky because the way to do it will be awk but having the "ignore case" comparison it is more difficult. Will try to find a moment to figure out how to do it.

logan Over a year ago

Thanks.. even if it is case sensitive its okay.. because its predefined structure file

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