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Use the -B option with grep

 
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# 1  
Old 04-03-2013
Use the -B option with grep
I am trying to parse out a file using grep - I would like to use the -B option so that the grep command prints the previous 2 lines if/when my string is matched - listed below are two examples - one with the info I want printed to a new file and one with info I want ignored. Any help with the grep -B command structure would be helpful.

Code:
______________________________________________________________________________
CAUAJM_I_50322 Checking Syntax for Inserting/Updating job: q_pm_d_bifind_curr_n2
CAUAJM_E_50442 Invalid attribute value for <priority>: Unexpected end of character string: Pri X--If job fails due to unable to allocate bytes of shared memory",restart. If fails f
or different reason,e-mail Oncall Database Management Production Systems Support.Product Mastering bifind pull for n2
CAUAJM_E_50246 JIL syntax check FAILED

Code:
CAUAJM_I_50322 Checking Syntax for Inserting/Updating job: q_feeds_d_dbqc_release_inact
CAUAJM_I_50247 JIL syntax check PASSED

# 2  
Old 04-03-2013
So, when FAILED, you want to see that line and the two previous?

Usually, you only need to write one rule - what to include. And you do not need a line of what not to include as it is the opposite of the first rule.
# 3  
Old 04-03-2013
Yes - when FAILED - I want to print two previous lines - I was showing what I didn't want to see and an example - I tried using grep 'string' -B 2 FILE but that is not working
# 4  
Old 04-03-2013
In what way is that 'not working'? Does it not have that option, or does it accept it yet misbehave somehow?

For systems which don't have -B, you can write a small awk script:

Code:
$ cat context.awk

# Recall N lines ago up to 9 lines
function last(N)
{
        if(N>L) return("");
        return(LINE[(L-N)%10]);
}

{ LINE[(++L)%10]=$0 } # Remember line for later

$0 ~ REGEX  {   for(N=2; N>=0; N--) print last(N);      }

$ awk -f context.awk REGEX="FAILED" inputfile

Use nawk on solaris.
These 2 Users Gave Thanks to Corona688 For This Post:
rbatte1 Ribosome
# 5  
Old 04-03-2013
I just prints line with matching string - not previous 2 lines
# 6  
Old 04-03-2013
It works fine here:

Code:
$ awk -f warnlog.awk REGEX="FAILED" - <<EOF
CAUAJM_I_50322 Checking Syntax for Inserting/Updating job: q_pm_d_bifind_curr_n2
CAUAJM_E_50442 Invalid attribute value for <priority>: Unexpected end of character string: Pri X--If job fails due to unable to allocate bytes of shared memory",restart. If fails f
or different reason,e-mail Oncall Database Management Production Systems Support.Product Mastering bifind pull for n2
CAUAJM_E_50246 JIL syntax check FAILED
EOF

CAUAJM_E_50442 Invalid attribute value for <priority>: Unexpected end of character string: Pri X--If job fails due to unable to allocate bytes of shared memory",restart. If fails f
or different reason,e-mail Oncall Database Management Production Systems Support.Product Mastering bifind pull for n2
CAUAJM_E_50246 JIL syntax check FAILED

$

Show exactly what you're doing, word for word, letter for letter, keystroke for keystroke.
This User Gave Thanks to Corona688 For This Post:
bjdamon
# 7  
Old 04-03-2013
Ok - I have it working now - thanks so much for your help.
 
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