Question

I have idsfile.csv which is a comma separated file of ids (with no new line characters in),
and I would like to grab only the lines from a second datafile.txt file
which have one of those ids in (surrounded by tabs).

Sample idsfile.csv:

000001,000002,000005,000007,000008,000009,000011,000021,000029,000040,...

Sample datafile.txt:

titl e1   000001   description1 
title2   000003   descr iption2 
ti tle3   000021   des cripti on3 
title4   000023   description4 

If I was doing this without having to read in the ids from a file I would try:

grep -Ev '/\t000001\t|\t000002\t|\t000003\t/' datafile.txt > output.txt

but I am unsure how to read in the comma separated values in a way that I could then use them in the regular expression.

Does anyone know how I might assemble this as a one line command query please? Perhaps with textscan?

Edit: Actually, if I changed idsfile.csv to have an id on each line (with a tab before and after), then would I line similar to this work please or, I expect, is the syntax quite wrong:

grep -Evf idsfile.csv datafile.txt > output.txt

Answer 1

The single line of data in idsfile.csv is hostile to this workflow – you will have to transform it into a series of lines. The Unix toolset is based around lines!

So, we need to transliterate the commas into newlines:

tr , '\012' < idsfile.csv > idsfile.lines
fgrep -f idsfile.lines datafile.txt

A POSIX-compliant ‘grep’ will also recognize:

grep -F -f idsfile.lines datafile.txt

You might even be able to get away with:

tr , '\012' < idsfile.csv |
grep -F -f - datafile.txt

This tells ‘grep’ to read the list of names to search for from its standard input.

Finally, if you’re using GNU grep, you could add ‘-w‘ to search for words – it will require the pattern to be surrounded by non-alphanumeric characters (spaces in the examples).
The ‘-w' option means that if a line in datatfile.txt contains

something 000002100  kkkk

the entry ‘000021’ will not select that line (without the ‘-w‘, it would be selected).