I need to log into multiple machines every now and then and its really annoying to set everything up from scratch. Here’s some simple things I did with bash scripting for automating most of my workflow.

Table of Contents

Bash basics

A bash must have the line #!/bin/bash on the 1st line to let the OS know that this is a bash script.

If statements

You can check for existence of environment variables and execute specfic things. To check whether a env variable exists, following syntax can be used:

If statements have the basic syntax:

if [ <some test> ]; then
elif [ <some test> ]; then

The square brackets in the above if statement are actually a reference to the command test. This means that all operators that test allows may be used here as well. See man test to the see capabilities of the test command.

Scripting protips

Checking env variables

You can just check whether env variables exist or not with if $VAR_NAME. You need to specify a call to test inside square brackets and specify -z if you want to check whether the variables does not exist and -n if you want to check if the variable exists.

For example, cheking if $SERVER_ENV variable exists or not will look like this:

if [-n "$SERVER_ENV"]; then
    echo "SERVER_ENV exists"

Checking for programs

If you want to check whether a particular program exists or not, use hash <command_name>.

For example, to see if git exists and print an error if not:

if ! hash git 2>/dev/null; then
    echo "Please install git before proceeding."
    exit 1