Hi,

This is probably a simple question:

I have two files, "filea", and "fileb". "filea" contains a list of customer numbers only, one in each record.

1234
1241
1250
4569
6433
etc.

"fileb" is a larger file containing the "complete" list of customer data with many more records in it, of which "filea" is a subset, that contains address info, phone, etc.

I want to use the list of customer numbers in "filea" to extract those customer's data from "fileb" and output the result into "filec".

I thought I could do something really simple like:

grep `cat filea` fileb > filec

but that didn't work. Any ideas?

Thanks, Mike.

You were on the right track.

Use the -f flag with grep to pass in a list of patterns from a file.

e.g.

grep -f filea fileb > filec


Just so you understand why your effort wouldn't work...

`cat filea` would expand to for example:

customer1
customer2
customer3

... your grep command would therefore be interpreted by the shell as being:

grep customer1 customer2 customer3 fileb > filec

The above would look for the pattern "customer1" in the files "customer2", "customer3" and "fileb". The output would be redirected to "filec". You would get errors in filec because the files you have stipulated do not exist.

HTH

Very nice... Thank you, this worked like a gem!