Creating while loop in bash that would run for specific time

Question

I'm interested in creating a while loop in bash (version: 3.2.57(1)-release) running on osx that would run for a specific number of seconds/minutes.

Example

For instance, I would like to create n files each with current date and time during the period of 5 seconds.

Approach

My loop structure would be fairly basic:

i=$cmd(date %ss)
j=$i + 10
while [ $i -lt $j ]
do
fileName=$cmd(cat /dev/urandom | env LC_CTYPE=C tr -cd 'a-f0-9' | head -c 32)
date > $fileName
i=date %ss
done

Problem

When I try to execute the script I get the following errors:

loop.sh: line 1: syntax error near unexpected token `('
loop.sh: line 1: `i=$cmd(date %ss)'

Desired results:

The i counter reflects seconds, the loop stops after 10 seconds
Random *.txt files with current date as the sole content are created in the current working directory

Try shellcheck.net first to clean up the syntax issues that don't require human feedback — that other guy
– that other guy, Commented Jun 21, 2016 at 21:50
Here's how to assigning command output to a variable: var=$(mycommand) e.g. var=$(date +%s) — that other guy
– that other guy, Commented Jun 21, 2016 at 22:27
@Konrad, SO is such a fast paced forum that I normally do much more reading of posts then answering, even if I know the answer the core group always post so fast I don't get a chance to. Anyway, while I was able to help you I wanted to say I learned something new with the method you chose to get the fileName and have added your technique to my code library. Thanks! — user3439894
– user3439894, Commented Jun 22, 2016 at 13:16

user3439894 · Accepted Answer · 2016-06-22 01:56:03Z

2

The following will yield what you stated under "Desired results".

#!/bin/bash

i="$(date +%s)"
j="$(( i + 10 ))"

while [ $i -lt $j ]; do
    fileName="$(cat /dev/urandom | env LC_CTYPE=C tr -cd 'a-f0-9' | head -c 32)"
    date > "${fileName}.txt"
    i="$(date +%s)"
done

edited Jun 22, 2016 at 1:56

answered Jun 21, 2016 at 23:20

user3439894

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