While loops

Run for period of time

#!/bin/bash

runtime="5 minute"
endtime=$(date -ud "$runtime" +%s)

while [[ $(date -u +%s) -le $endtime ]]
do
    echo "Time Now: `date +%H:%M:%S`"
    echo "Sleeping for 10 seconds"
    sleep 10
done

Resource: https://www.golinuxcloud.com/run-while-loop-until-specific-time-shell-bash/

Infinite loop

item=true
while [ $item = true ]; do echo 'bla'; done

While value is an empty string

value=""
while [[ -z "$value" ]]; do
    echo "value is empty"
    # here's where we break out
    if [[ "$value" ]]; then
        echo "exiting loop because value has been set to $value"
        break
    fi
done

Read each line of a file

while read p; do
  echo "$p"
done <file.txt

Resource: https://stackoverflow.com/questions/1521462/looping-through-the-content-of-a-file-in-bash

One-liner equivalent

while read t; do echo "$t"; done <bbh_targets.txt

Execute command once per line of piped input

command | while read -r line; do command "$line"; done

For example, if you want to run a program and send the output to different files using regular expressions:

recon asn -t recon_targets.txt | \
  while read -r line; do \
    ([[ $line =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\/[0-9]{2}$ ]] \
    && echo $line | anew ip_ranges.txt) || ([[ $line =~ ^[0-9]{5}$ ]] && \
      echo $line | anew asns.txt); done

Resources: https://unix.stackexchange.com/questions/7558/execute-a-command-once-per-line-of-piped-input Tool run for the example