Question

Use case: I want to pass an email message from procmail to a shell script and have the script store the Subject: header value as one variable and the Return-Path: header value.

As a test, I’m using the following script:

#!/bin/bash
while read data; do
        SearchCriteria1=$(echo "$data" | grep "Subject: " | cut -c 9-)
        SearchCriteria2=$(echo "$data" | grep "Return-Path: " | cut -c 13-)
        echo "$SearchCriteria1" > test.1
        echo "$SearchCriteria2" > test.2
done

The echo statements are just a test. I plan to use the variables later in the script.

When I try this though, test.1 and test.2 just have blank lines. I know I’m missing something obvious. Can someone please point me in the right direction?

Answer 1

For every line, you grep the line, leaving you either with the line or no line. Then you overwrite a file with that line (which will likely be empty most iterations). So if both those files are empty, the last line of input contains neither Subject: or Return-Path:.

This is probably how I’d do it:

#!/usr/bin/env bash
while read -r key value; do
    case $key in 
        Subject:) subject=$value;;
        Return-Path:) return_path=$value;;
    esac
done
echo "<$subject> <$return_path>"

I say probably because I don’t know what the input will look like.

See also http://mywiki.wooledge.org/BashFAQ/001