Bash, the Bourne Again Shell, is one of the most ubiquitous shells on nix systems, being either the default or included in distributions.
If you use bash a lot, you will find that make can also be used for lots of things.
To run a command in an infinite loop, do something like this: while true; do echo hi mom; sleep 1; done
To run a command a set number of times, do: for i in {1..10}; do echo howdy; sleep 1; done
To redirect stdout and stderr from a command: foo > /dev/null 2> err.txt
To pass along your arguments when creating a wrapper: wrapped-script "$@"
To compare two strings: if [[ "$1" = "$2" ]] ; then ...
To do a basic if-then/else check on a file exist:
if ! test -d /path/to/file ; then
echo it does not exist;
else
echo exists;
fi
This is what a simple bash script template might look like.
It does a variety of things, just remove the sections you don't care for.
#!/bin/bash
set -euo pipefail
# add -x to trace
# help function
function show_help() {
cat <<- EOF
USAGE: my-script [--foo foo] [--bar bar] [--flag] args...
OPTIONS:
--foo - do foo
--bar - do bar
--flag - set flag
EOF
exit
}
# handle options as flags, key/value or positional arguments
POS_ARGS=()
FLAG_SET=false
while [[ $# -gt 0 ]]; do
key="$1"
case $key in
--flag)
FLAG_SET=true
;;
--foo)
shift
FOO="$1"
;;
--bar)
shift
BAR="$1"
;;
--help)
show_help
;;
*)
POS_ARGS=[${#POS_ARGS[@]}]="${1} "
;;
esac
shift
done
# figure out where the script is at to call other files around it
self=$(readlink -f "${BASH_SOURCE[0]}") # follow link
echo full path is $self
echo dir name is $(dirname $self)
echo base name is $(basename $self)
# full path is /Users/someone/scratch/my-script
# dir name is /Users/someone/scratch
# base name is my-script
set -euo means 'exit immediately', 'treat unset variables as errors on parameter expansion', 'option pipefail' (return value of rightmost non-zero result in pipes).
Happy scripting!