Bash

Run command after n seconds

Open will start after two secs without blocking execution

( sleep 2 && open http://0.0.0.0:8000/ )&

Expand bash variable containing a path with spaces

SKETCH_PLUGINS_DIRECTORY="$HOME/Library/Application Support/com.bohemiancoding.sketch3/Plugins/" 

# To avoid the expasion to be splitted into two strings, we surround it with ""

ls "$SKETCH_PLUGINS_DIRECTORY"

ls just one column

ls -1

Check if last command succeeded

some_command
if [ $? -eq 0 ]; then
    echo OK
else
    echo FAIL
fi

Count arguments passed to a script

if [ "$#" -ne 1 ]; then
    echo "Illegal number of parameters"
fi

Check if directory exists

To check if a directory exists in a shell script you can use the following:

if [ -d "$DIRECTORY" ]; then
  # Control will enter here if $DIRECTORY exists.
fi

Or to check if a directory doesn’t exist:

if [ ! -d "$DIRECTORY" ]; then
  # Control will enter here if $DIRECTORY doesn't exist.
fi