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Month: February 2020

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How to use `find` to search for files based on modification time?

February 16, 2020March 10, 2020 Fabrice

To find the files older than 17 days: $ find . -daystart -mtime +17 -print The reason to use `-daystart` is to make things more natural for human beings, because `find` performs some rounding; from the man page: When find… Read More

Bash

How to have a dynamic variable name in bash?

February 12, 2020March 10, 2020 Fabrice

Code snippet below: myvar=something varname=myvar echo ${!varname} I work as a freelancer, so if you don’t want to do that kind of things yourself or don’t have the time, just drop me a line to hire me.

Bash

How to perform a lock/mutex in bash?

February 3, 2020March 10, 2020 Fabrice

This can be done using the `ln` command: tempfile=$(mktemp ./lock.XXXXXX) lockfile=./lockfile trap "rm $lockfile" EXIT try=1 while ! ln $tempfile $lockfile > /dev/null 2>&1; do try=$[ $try + 1 ] if [[ $try -gt 10 ]]; then echo "ERROR: Timeout… Read More

Bash

How to test that an environment variable is set in Bash?

February 3, 2020March 10, 2020 Fabrice

Use this: ${THEVAR:+x} Which will expand to “x” if THEVAR is set and not empty. Alternatively, this test can be used: if [[ ! -v THEVAR ]]; then echo "THEVAR is not set" fi But that will work even if… Read More

Bash

Recent Posts

  • How to persist variables in a loop from a find command in Bash?
  • How to iterate an array in Bash?
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  • How to install jq on CentOS?
  • Magic SysRq cheatsheet

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