Advanced bash

brace expansion

https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html

echo a{b,c}d
# abd acd

mkdir tmp/{a,b}/c
# tmp/a/c, tmp/b/c

run & interrupt parallel commands

https://stackoverflow.com/questions/3004811/how-do-you-run-multiple-programs-in-parallel-from-a-bash-script

# start three progx in parallel, and make sure these can be killed in one ctrl-c
(trap 'kill 0' SIGINT; 
prog1 & 
prog2 & 
prog3
)

kill 0: a special command to kill all processes in the current group (usually this means all programs started in the current shell).

The trap command will wait until caught the signal SIGING and then call the command kill 0, another example:

# Run something important, no Ctrl-C allowed.
# "" means run nothing, thus ignore the signal.
trap "" SIGINT
important_command

# Less important stuff from here on out, Ctrl-C allowed.
# - is used to reset the default behaviour
trap - SIGINT
not_so_important_command