Question

I am reading some equipment configuration output and check if the configuration is correct, according to the HW configuration. The template configurations are stored as files with all the params, and the lines contain regular expressions (basically just to account for variable number of spaces between “object”, “param” and “value” in the output, also some index variance)

First of all, I cannot use grep -f $template $output, since I have to process each line of the template separately. I have something like this running

while read line
  do
  attempt=`grep -E "$line" $file`
  # ...etc
  done < $template

Which works just fine if the template doesn’t contain regex.
Problem: grep interpretes the search option literally when these are read form file. I tested the regex themselves, they work fine from the command line.

With this background, the question is:

How to read regex from a file (line by line) and have grep not interprete them literally?

Answer 1

Using the following script:

#!/usr/bin/env bash
# multi-grep
regexes="$1"
file="$2"
while IFS= read -r rx ; do
    result="$(grep -E "$rx" "$file")"
    grep -q -E "$rx" "$file" && printf 'Look ma, a match: %s!\n' "$result"
done < "$regexes"

And files with the following contents:

$ cat regexes
RbsLocalCell=S.C1.+eulMaxOwnUuLoad.+100

$ cat data
RbsLocalCell=S1C1 eulMaxOwnUuLoad 100

I get this result:

$ ./multi-grep regexes data
Look ma, a match: RbsLocalCell=S1C1 eulMaxOwnUuLoad 100!

This works for different spacing as well

$ cat data
RbsLocalCell=S1C1    eulMaxOwnUuLoad           100

$ ./multi-grep regexes data
Look ma, a match: RbsLocalCell=S1C1    eulMaxOwnUuLoad           100!

Seems okay to me.