Your first Mac shell script (zsh), and running it automatically with launchd

Apple’s support page says Macs have used zsh as the default login and interactive shell since macOS 10.15 Catalina; bash was the default in 10.14 and earlier. Most simple scripts work in either.

1. Write it

In Terminal:

mkdir -p ~/Scripts
nano ~/Scripts/hello.sh

Paste this, then press Ctrl-O, Return, Ctrl-X to save and quit:

#!/bin/zsh
# hello.sh - greet, show free disk space, list the 5 newest Downloads
echo "Hello from zsh! It's $(date '+%A %d %B, %H:%M')."
df -h / | tail -1 | awk '{print "Free space on the startup disk: " $4}'
ls -t ~/Downloads | head -5

The first line, #!/bin/zsh, is the shebang. It tells macOS which program should run the file.

2. Make it executable and run it

chmod +x ~/Scripts/hello.sh
~/Scripts/hello.sh

chmod +x marks the file as runnable. Without it you’ll get permission denied.

To run it by name from anywhere, add the folder to your PATH:

echo 'export PATH="$HOME/Scripts:$PATH"' >> ~/.zshrc
source ~/.zshrc
hello.sh

3. Double-clickable version

Rename a copy to hello.command. Double-clicking a .command file in Finder opens Terminal and runs it. It still needs chmod +x.

4. Run it automatically with launchd

macOS uses launchd for scheduled and background jobs. Apple’s guide describes where job files go:

Folder	What goes there
~/Library/LaunchAgents	Agents for your account only. Apple describes a user agent as specific to one logged-in user, running only while that user is logged in. This is what you usually want.
/Library/LaunchAgents	Agents loaded for every user who logs in. Files here must be owned by root, so you need admin rights to install them.
/Library/LaunchDaemons	System-wide daemons, loaded when the Mac starts up rather than at login. Also root-owned.

Create ~/Library/LaunchAgents/com.example.hello.plist:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>Label</key><string>com.example.hello</string>
  <key>ProgramArguments</key>
  <array><string>/Users/YOUR-USER/Scripts/hello.sh</string></array>
  <key>StartCalendarInterval</key>
  <dict><key>Hour</key><integer>9</integer><key>Minute</key><integer>0</integer></dict>
  <key>StandardOutPath</key><string>/tmp/hello.log</string>
  <key>StandardErrorPath</key><string>/tmp/hello.err</string>
</dict>
</plist>

Then load it and test it:

plutil -lint ~/Library/LaunchAgents/com.example.hello.plist      # checks the file for typos
launchctl bootstrap gui/$(id -u) ~/Library/LaunchAgents/com.example.hello.plist
launchctl kickstart gui/$(id -u)/com.example.hello             # run it right now
cat /tmp/hello.log

To unload it: launchctl bootout gui/$(id -u)/com.example.hello.

Other triggers (the first three are covered in Apple’s guide; all four are in man launchd.plist):

• StartInterval: every N seconds.
• StartCalendarInterval: a cron-style time. Any key you leave out means “every”.
• WatchPaths: run whenever a file or folder changes.
• RunAtLoad: run when the job is loaded, i.e. at login for an agent.

Gotcha: launchd doesn’t load your ~/.zshrc, so your PATH and aliases aren’t there. Use full paths inside scheduled scripts (/usr/bin/rsync, /opt/homebrew/bin/...). If a script needs files in protected folders like Desktop or Documents, macOS may block it until you grant access under System Settings → Privacy & Security.

Next steps

• A full real-world LaunchAgent that keeps NAS shares mounted: Auto-mount NAS shares on a Mac.
• More shell, AppleScript and Shortcuts links: Scripting & Automation.