Unix command for extracting lines befor and after a particular searched string pattern

unix grep

11,051

Solution 1

For three lines before and after the match

grep -C 3 pattern filename

For more control on number of after and before lines to be displayed for a match, use

grep -A (num of after) -B (num of lines before)  pattern filename

From man grep:

 -A NUM, --after-context=NUM
          Print NUM lines of trailing context after matching lines.  
          Places a line containing -- between contiguous groups of matches.

   -a, --text
          Process a binary file as if it were text; 
          this is equivalent to the --binary-files=text option.

   -B NUM, --before-context=NUM
          Print NUM lines of leading context before matching lines.  
          Places a line containing -- between contiguous groups of matches.

   -C NUM, --context=NUM
          Print NUM lines of output context.  
          Places a line containing -- between contiguous groups of matches.

Solution 2

Grep has options to display rows immediately before and after the match. The numbers in the command line below are the appropriate number of rows to display, after and before the match. E.g.

grep -A3 -B5 yoursearchpattern inputfilepattern

man grep is useful for details about the options.

Assuming you have GNU grep, to check you can use --version option:

> grep --version
GNU grep 2.6.3

11,051

Author by

wanted

Updated on June 29, 2022

Comments

wanted almost 2 years

How can I search for lines in a file and extract the lines above and below lines of the searched line .

My input is like

Tue Jun 26 14:59:46 2012
 Warning ffffffff act_msg_ctms_remove_from_pending_queue: deleting message 44817201 from the queue.
Tue Jun 26 14:59:46 2012
 Warning ffffffff Finishing processing record number 44817201
Tue Jun 26 14:59:46 2012
 Warning  5000000 activity_queue_manager_finish_cb: unknown activity 120.
Tue Jun 26 14:59:46 2012
 Warning ffffffff Activity State Machine priority (2) finished
Tue Jun 26 14:59:46 2012
 Warning ffffffff 
====================================================
Processing database file "INCOMING_MESSAGES" record number 47810234 from user "(unknown)"
Tue Jun 26 14:59:46 2012
 Warning ffffffff ACTIVITY data: rec_num (47810234) size (116) 
Tue Jun 26 14:59:46 2012
 Warning ffffffff activity status: ACT_SENT 
Tue Jun 26 14:59:46 2012
 Warning ffffffff MESSAGE body "MVT
QFA6673/26.VHQOS.BNE
EA0541
"
Tue Jun 26 14:59:46 2012
 Warning ffffffff Finishing processing record number 47810234
Tue Jun 26 14:59:46 2012
 Warning ffffffff Activity State Machine priority (1) finished
Tue Jun 26 14:59:46 2012
 Warning ffffffff 
End processing record number 47810234

====================================================

And I require my output to be like

/

Tue Jun 26 14:59:46 2012
 Warning ffffffff MESSAGE body "MVT
QFA6673/26.VHQOS.BNE
EA0541"

/

My search string would be MVT.

Pls help

jpe almost 12 years

Thanks, +1 for the -C option, been using A and B, learned a new letter today!
pyfunc almost 12 years

@jpe: But using A and B was the correct answer to the questions since his context lines for after and before differs. :)
wanted almost 12 years

In both of these cases its throwing up an error called illegal option
pyfunc almost 12 years

@wanted: This is for gnu grep. Which grep are you using?