launchd - how to keep script running in the background

Question

I have a simple script to upload the file to dropbox whenever it changes. I wanted to run it at system startup and keep it in a background to let the script watch the file.

I've created a plist, however it runs the script and exits with code 0.

plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//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.launchd.dropbox_uploader</string>
    <key>ProgramArguments</key>
    <array>
        <string>sh</string>
        <string>-c</string>
        <string>~/dropbox-uploader.sh; wait</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
</dict>
</plist>

(doesn't work neither with, nor without wait in the command)

script (it works fine and doesn't exit when run in command line)

#!/bin/sh

fswatch -o ~/file.txt | xargs -n1 -I{} curl -X POST https://content.dropboxapi.com/2/files/upload \
    --header 'Authorization: Bearer XXXXX' \
    --header 'Content-Type: application/octet-stream' \
    --header 'Dropbox-API-Arg: {"path":"/backup/file.txt","strict_conflict":false,"mode":{".tag":"overwrite"}}' \
    --data-binary @'~/file.txt'

launchtl list output

 ~> launchctl list | grep com.example                                                                                                                       (base) 
-   0   com.example.launchd.dropbox_uploader

How to achieve my goal to have it run in the background? I'm not sure if there's an issue with my plist or script.

Answer 1

Enabling the file output as Gordon mentioned in his comment helped to find the reason.

The issue was:

/Users/me/dropbox-uploader.sh: line 3: fswatch: command not found

So changing fswatch to the absolut fswatch bin path /usr/local/bin/fswatch solved the problem. I've also replaced ~/ with the absolute path in the plist and made sure that script is executable.

Final script:

#!/bin/sh

/usr/local/bin/fswatch -o ~/file.txt | xargs -n1 -I{} curl -X POST https://content.dropboxapi.com/2/files/upload \
    --header 'Authorization: Bearer XXXX' \
    --header 'Content-Type: application/octet-stream' \
    --header 'Dropbox-API-Arg: {"path":"/backup/file.txt","strict_conflict":false,"mode":{".tag":"overwrite"}}' \
    --data-binary @'~/file.txt'

plist with file output enabled

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//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.launchd.dropbox_uploader</string>
    <key>ProgramArguments</key>
    <array>
        <string>/Users/me/dropbox-uploader.sh</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
    <key>StandardOutPath</key>
    <string>/Users/me//dropbox.out</string>
    <key>StandardErrorPath</key>
    <string>/Users/me/dropbox.err</string>
</dict>
</plist>