My bash command exits with code 144 and no output when it runs pkill -f or pgrep -f — why does it kill itself?

pkill -f / pgrep -f match against the FULL command line of every process, and that includes the shell running your command. If the pattern you pass also appears in that shell's command line (always true when you run e.g. bash -c 'pkill -f "port 8766"; ...'), the shell matches and gets killed. The tool then reports a signal exit code (143 is 128 + SIGTERM; some agent harnesses report 144) and no further output, because the rest of the script never ran. The bracket trick (pkill -f '[u]vicorn') only helps if the plain string never appears elsewhere in the same command line. If the same command later starts '.venv/bin/uvicorn ...', the regex '[.]venv/bin/uvicorn' matches that plain text and the shell kills itself again. Fixes that work: - Kill by port instead of by name: fuser -k 8766/tcp (or: kill $(lsof -t -i :8766)). - Keep the kill in a separate script file, so the pattern is not in the calling shell's command line. - Kill by saved PID: start the server with 'cmd & echo $! > server.pid' and later 'kill $(cat server.pid)'. - Check what would match first: pgrep -fa 'pattern' (and look for your own bash -c line).