Scripting Basics

What it is

A script is a text file of commands that a computer runs in order. Scripts automate repeated tasks, such as mapping drives, installing software or collecting system information. A technician does not need to write large programs, but must recognise script types, read simple scripts and know the risks.

How it works

Script file types

On Windows, the file extension tells the operating system which interpreter to use. A shell script on Linux often starts with a line such as #!/bin/bash, which names the shell.

Common uses

• Restarting machines or services.
• Remapping network drives at sign in.
• Installing applications and updates in bulk.
• Automating backups.
• Gathering system information.
• Starting scheduled maintenance tasks.

Basic building blocks

Comments are notes for people that the computer ignores. Batch uses REM, shell and PowerShell and Python use #, and VBScript uses an apostrophe.

Variables hold values. Data types include numbers (integers) and text (strings). Environment variables hold system values such as the user's folder.

Conditions run a command only if a test is true. Loops repeat commands for each item or until a condition changes.

Examples

Batch file (Windows Command Prompt):

@echo off
REM Map a drive and copy a file
net use Z: \\server\share
copy C:\Reports\daily.txt Z:\

PowerShell:

$name = "report"
if (Test-Path "C:\Temp\$name.txt") { Write-Output "found" } else { Write-Output "missing" }

Linux shell:

#!/bin/bash
# List log files
for f in *.log; do
  echo "$f"
done

In the PowerShell example, $name is a variable and the if is a condition. In the shell example, the for is a loop. The variable $HOME is an environment variable in Linux and macOS, %USERPROFILE% is one in the Windows Command Prompt, and $env:USERPROFILE is the PowerShell form.

Running a script

In Windows, a batch file can be run by double clicking it or by typing its name in a Command Prompt. PowerShell has an execution policy, which controls whether scripts are allowed to run, and it is a safety setting. In Linux and macOS, a script must have the execute permission, set with chmod +x script.sh, and is run with ./script.sh.

Risks and good practice

Read a script before you run it. Test on a single non critical machine first. Keep scripts in version control or a known location, and run them with the least privilege that works.