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[solved] Diff between two files by grep

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Top Forums Shell Programming and Scripting [solved] Diff between two files by grep
# 8  
Old 08-02-2010
I suggest to get a shell reference, if you need to program scripts often. In bash: GNU bash manual - GNU Project - Free Software Foundation (FSF), available on-line and in several formats to be downloaded.
As scottn said, [-z] option checks whether length of string is 0. You can find out many other conditional expressions in: Bash Conditional Expressions

Albert.
# 9  
Old 08-02-2010
Hi Albert/All,

I have few queries regarding the code as i was a shell scirpt begginer,

(1) In while loop we are checking whether the line exist or not then why we again checking in if loop
(2) I tried the code by removing z option then the output totaaly changing,as we are using -z to find length why the output changes

output with out using -z
Code:
A BONES RD,NHILL,3418,VIC
37TH PARALLEL RD,DEEP LEAD,3385,VIC
4 AK RD,OAKEY,4401,QLD
A & J FARRS RD,BARMOYA,4703,QLD
A B PATTERSON DR,ARUNDEL,4214,QLD

feelmyfrd
# 10  
Old 08-02-2010
Hi.

(1) it's not necessary
(2) by removing -z you've negated the result (i.e. to get all the lines in file2 that are in file1)

You can also do this in awk (nawk or /usr/xpg4/bin/awk on Solaris):

Code:
$ awk 'NR == FNR {A[$0]=1; next} !A[$0]' file2 file1 > file3


A BLAIRS RD,BUCKRABANYULE,3525,VIC

# 11  
Old 08-02-2010
Hi,

In script I posted I checked whether a line is in the other file. To do that I just check its length. If length is 0 it means grep has no output. So, that line is not in file2, and it can be printed to file3. In two steps:
Code:
exists=īgrep "$line" file2.txt`   ##finds "$line" in file2
if [ -z $exists ]; then             ## Test whether $exists has length 0
   echo $line >> file3.txt         ## If so, line is not in file2. Then I print to file3
fi

Maybe for you it's easier to understand scottn script, or ramkrix simpler way using sdiff.

Albert.
# 12  
Old 08-02-2010
Hi All,

The script working fine now I understood clearly the codes including albert code

Thanks a lot..
feelmyfrd
# 13  
Old 08-03-2010
I can use :
Code:
grep -v -f file1 file2 -x
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