jobs - macOS

Overview

The jobs command in macOS is used to list the status of jobs in the current terminal session. A job can refer to processes that have been started directly or put into background from the command line. This tool is particularly useful in managing multitasking and monitoring the background and suspended tasks, allowing users to view their progress and state without switching to each task individually.

Syntax

The basic syntax of the jobs command is:

jobs [options] [job_id ...]
  • job_id specifies the particular job’s ID which you want to examine; if omitted, jobs will display information about all jobs.

Options/Flags

The jobs command supports a few options that control its output:

  • -l: Lists process IDs in addition to the normal information.
  • -p: Lists only the process ID of the job’s process group leader.
  • -n: Reports only on jobs that have changed status since the user was last notified of their status.
  • -r: Reports only running jobs.
  • -s: Reports only stopped jobs.

Examples

  1. Basic Usage
    List all active jobs:

    jobs
  2. Detailed Job List
    List all jobs with their process IDs:

    jobs -l
  3. Specific Jobs
    To check the status of a job with a specific job ID, use:

    jobs %1
  4. Filter Running Jobs
    To display only running jobs:

    jobs -r

Common Issues

  • Misunderstanding Job IDs: Users often confuse process IDs with job IDs. A job ID is specific to the shell’s job control, while process IDs are system-wide.
  • Using Jobs in Scripts: jobs is designed for interactive use. In scripts, processes are usually handled directly via their PIDs or other mechanisms.
  • No Output: If jobs returns no output, it generally means there are no jobs in the background or stopped. Ensure that jobs are running or stopped in the background.

Integration

The jobs command can be combined with other commands for robust process management:

# Send a SIGTERM to all running jobs
kill $(jobs -p)

You can also use it in script loops to automate handling of tasks:

for job in $(jobs -p); do
    kill -9 $job
done
  • bg: Resumes suspended jobs in the background.
  • fg: Brings jobs to the foreground for interactive processing.
  • kill: Send signals to specific jobs.
  • ps: Provides detailed information about currently running processes.

For further reading and more detailed information, consult the job control section of the bash man page or relevant online resources.