Creating variables dynamically and using it in script?

Hi,

I have a problem that I am trying to solve and would greatly appreciate some input to solve this. I have a file containing variable length of line. Each line in the file has values separated by "," and i need to grep for these values in a some files. For example below is a sample file with 3 lines:

file1:a,b,c,d
file2:e,f
file3:g,h,i,j,k,l

I have gone pass to read this file line by line but how do i pass each value separated by "," to variable and use it in a grep command.

So basically i need to dynamically generate variables and pass it to grep command for further processing like:

for a,b,c
grep "$var" file1

for e,f
grep "$var" file2

for g,h,i,j,k,l
grep "$var" file3

Any help on this would be greatly appreciated. Can we use Arrays?

Thanks in advance.

Arrays may be a good idea in this instance. However array implementations vary between the various shells. What shell are you using?

#!/bin/bash

Can pls give an example of doing this? I am trying to use array but have not had success , may be missing something.

Since you have BASH you probably have egrep. It accepts multiple expressions like "a|b|c|d".

You can use IFS to split apart a string on ",", then put it back together with "|"

Since IFS changes how any splitting works in the shell you will want to put it back to what it was after!

#!/bin/bash

OLDIFS="$IFS"

while IFS=":" read FILE STRING
do
        IFS=","
        ARR=( $STRING )
        IFS="|"
        echo egrep "${ARR[*]}" $FILE
done < filename

IFS="$OLDIFS"

$ ./script.sh

egrep a|b|c|d file1
egrep e|f file2
egrep g|h|i|j|k|l file3

$

Remove the 'echo' to have it actually run egrep instead of just printing it.

@Corona688 - Nice idea to use egrep, I was going to recommend awk for that bit.

Thanks, this resolves partial problem but now struck with egrep.

egrep a|b|c|d file1

does not work. Is there any other way i can do this. Only way I can think of is using a loop, to loop over an array, but would appreciate if you have anything else.

In what way does it "not work". Be specific! :wall: If it's a bug I can probably fix that with more information. If you don't actually have it, say so.

Sorry my bad, I should have been more specific. This is what i see when run the command

egrep a|b|c temp.log
-bash: a: command not found
-bash: b: command not found

The command prompt does not return after that, untill i hit CTRL+C. Is it that egrep is not allowed by my system?

That doesn't work because "a|b|c" is not in quotes. It has to be, or the shell assumes you're running

egrep a | b | c

It freezes because 'egrep a' is not given a filename and tries to read from standard input.

Kudos for trying to test the solution instead of just copypasting though!

You definitely have egrep.

Perhaps the debug output line should have been:

echo egrep \""${ARR
[*]}"\" $FILE

Giving:

$ ./script.sh

egrep "a|b|c|d" file1
egrep "e|f" file2
egrep "g|h|i|j|k|l" file3

$

Thanks guys...it really helped. Appreciate your help

---------- Post updated 10-19-11 at 04:56 PM ---------- Previous update was 10-18-11 at 05:16 PM ----------

One more question to related to the egrep. Your earlier suggestions work fine, but I have a little more complex issue. Like earlier suggested in am using

egrep "a|b|c|d" file1 

and it works fine, but it also get the other matching patterns of a. For example my file also has some text like:

xxxayyy , xyza and a 

Currently it gets every thing like: "xxxayyy", "xyza" and "a" and I just want to get "a" from the file and not other text can you please suggest how can i use the above " egrep" to filter these and not .

Thanks in advance ...

Try using the \b word boundries like this:

egrep "\ba\b|\bword\b" files

Thanks guys.... you guys are amazing. Please continue the good work.