A simple bash cheat sheet

bash-commands.sh

#!/usr/bin/env bash

###
### Some terminal colors
### usage: echo -e "${GREEN}Hello, this should be green! $RESET"
###
export BLACK="\033[30m"
export GRAY="\033[1;30m"
export RED="\033[31m"
export GREEN="\033[32m"
export YELLOW="\033[33m"
export BLUE="\033[34m"
export CYAN="\033[36m"
export UNDERLINE="\033[4m"
export RESET="\033[0m"
export CLEAR_LINE="\r\033[K"


### Getting the current directory into a variable
CURRENT_DIR=$(pwd)
### Returning to the original directory we saved
cd $CURRENT_DIR

###
### Iterating over an array of strings
###
MY_STRINGS=("first" "second" "third")
for s in "${MY_STRINGS[@]}"; do
  echo "$s"
done


###
### Functions
###
some_function() {
  echo "This does something interesting..."
  echo "The first parameter sent to this function was $1"
  echo "...and the second parameter was $2"
}
### Calling the function with parameters
some_function "first_param" "second_param"

###
### Conditions
###

### equality
if [ $SOME_PARAM == "hello" ]; then     # The spaces around the '==' are necessary!
  echo "$SOME_PARAM is 'hello' "
fi
# or this way
if [ $SOME_PARAM -eq "hello" ]; then
fi
### not equal
if [ $SOME_PARAM -ne "hello" ]; then
  echo "not equal"
fi


### string null or empty
if [ -z $SOME_PARAM ]; then
  echo "$SOME_PARAM is null or empty"
fi

### logical 'or' and logical 'and' operators respectively
if [ $SOME_PARAM -o $ANOTHER_PARAM ]; then
  echo "one of them was true"
fi
if [ $SOME_PARAM -a $ANOTHER_PARAM ]; then
  echo "both of them were true
fi