Automatically relaunch a closed macOS application

Question

I have an application that opens when I log in.

Is there a way to relaunch it automatically if it crashes or if I close it inadvertently?

The application in question is Transmission, if there is any solution specific to this app.

In a perfect world, it could even be launched even without me opening a session.

Answer 1

Here is my launchd script to keep SomeApp always running.

Name it SomeApp.restart.plist and place it in ~/Library/LaunchAgents/

<?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>RunAtLoad</key>  
        <true/>  
        <key>KeepAlive</key>
        <true/>
        <key>Label</key>
        <string>SomeApp.restart</string>
        <key>ProgramArguments</key>
        <array>
                <string>/path/to/SomeApp.app/Contents/MacOS/SomeApp</string>
        </array>
</dict>
</plist>

Load it once with

launchctl load ~/Library/LaunchAgents/SomeApp.restart.plist

Launchctl will run this after reboots.

• RunAtLoad will launch the application the first time launchctl runs this
• KeepAlive will restart it if the application quits (CMD+Q or crash)

Should run forever. If you want a GUI tool to help, Lingon works even though development has stopped.

Answer 2

You could write a launchd script to do it. Launchd can watch for applications and restart them if they disappear. I might have one somewhere if you are interested.

Updated with an example...

See mankoff's example. Here's mine, it's slightly different but works the same...

<?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>RunAtLoad</key>  
    <true/>  
    <key>KeepAlive</key>  
    <true/>  
    <key>Label</key>  
    <string>keep.it.running</string>  
    <key>Program</key>  
    <string>/Applications/Address Book.app/Contents/MacOS/Address Book</string>  
</dict>  
</plist>  

Answer 3

You can open applications on the background with open -jg or the launch command in AppleScript.

#!/bin/bash

open -jg -a FastScripts -a Mail
osascript -e 'launch app "Alfred"'

KeepAlive is not needed. RunAtLoad would also run the program on the zeroth interval.

<?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.stackexchange.apple.837</string>
    <key>Program</key>
    <string>/Users/username/Library/Scripts/open applications.sh</string>
    <key>StartInterval</key>
    <integer>1</integer>
</dict>
</plist>