[SOLVED] Escape double and single quotes in Bash

Issue

I have a Cron Job running quarterly on every first Sunday of the Month:

0 0 1-7 3,6,9,12 * [ "$(date '+\%a')" == "Sun" ] && /script.sh

Now I want to install it automatically using echo like:

(crontab -l ; echo "0 0 1-7 3,6,9,12 * [ "$(date '+\%a')" == "Sun" ] && /script.sh") | crontab -

while escaping \"Sun"\ works fine I can't escape "$(date '+\%a')" as this is a mix of single and double quotes with \ within double quoted echo command.

Solution

You don't need to use crazy escaping. Use [[ ... ]] provided by bash instead of old (and error prone) [ ... ]:

So use:

0 0 1-7 3,6,9,12 * [[ $(date +\%a) == Sun ]] && /script.sh

And to install it automatically use:

(crontab -l ; echo '0 0 1-7 3,6,9,12 * [[ $(date +\%a) == Sun ]] && /script.sh') | crontab -

PS: Make sure to set SHELL=/bin/bash in the crontab file before this line.

Answered By - anubhava

Answer Checked By - Robin (WPSolving Admin)