where absence of string in a log file, send email. validating inputs

Question

The following bash script attempts to read a file and search for the given string. in this instance, the case should generate a positive result In case of zero length, i.e. the string is not found, then send an email using Postfix (as send-only).

#!/bin/bash

results=$(grep "Parameters: {\"id_at_chain\"=>\"001142\", \"articles\"" ~/makt/current/log/production.log)
lines=($results)
if [ -z "$results" ]; then
  echo "array articles 001142 missing" | mail -s "problem 001142" [email protected] [email protected]
fi

What I want to do is put some verification code in order to test (and possibly dump to a log file):
• whether the file is found
• whether $results exists
• the length of $results

I can echo $results and it gives the expected result, however
echo -z "$results" seems to output $results not the length

Answer 1

I think the issue is that you think [ is some shell syntax, rather than it being a command. Another way to write your code is to say

if test -z "$results" ; then

and then it might be more obvious that -z is a flag to the [ or test command.

You get the output of the grep command into a string called results, and you then create a one element array called lines which contains this string. Presumably you have some plan for lines but at the moment it is just a distraction.

As for your bullet points

• [ -e ~/makt/current/log/production.log ] can tell you if the file exists
• $results always exists, it might be empty of course but you create it.
• ${#results} is the number of characters in $results