Summary: Bash hints, tips, oneliners and best practices.
Date: 8 December 2024

grep file without empty lines and comments

grep -v '^\s*$\|^\s*\#' postgresql.conf

find file in current and subdirectories

sudo find . -name main.cf

display all crontabs for all users as root sudo su -

for user in $(cut -f1 -d: /etc/passwd); do echo $user; crontab -u $user -l; done

Note this is especially useful in pipelines

set

# -e : exit the script if any command fails
# -u : treat unset variables as errors and exit
# -o pipefail : ensure the entire pipeline fails if any command within it fails
# -x : print all the commands to the terminal
# -v : print all lines without variable resolution
# - For all, to disable use +, for example `set +v`
set -euo pipefail

Compare two files

diff file file2

Compare two files next to each other, only differences

diff -y --suppress-common-lines file1 file2

for i in `ls -1 | grep was-`; do if [ -f $i/.run ]; then echo start slot $i; fi; done

• ls -1 lists all files and directories each on a separate line
• [ -f ] is true if listed file is a regular file