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7.2 Job Control Builtins

bg ¶

bg [jobspec …]

Resume each suspended job jobspec in the background, as if it had been started with ‘&’. If jobspec is not supplied, the current job is used. The return status is zero unless it is run when job control is not enabled, or, when run with job control enabled, any jobspec was not found or specifies a job that was started without job control.

fg ¶

fg [jobspec]

Resume the job jobspec in the foreground and make it the current job. If jobspec is not supplied, the current job is used. The return status is that of the command placed into the foreground, or non-zero if run when job control is disabled or, when run with job control enabled, jobspec does not specify a valid job or jobspec specifies a job that was started without job control.

jobs ¶

jobs [-lnprs] [jobspec]
jobs -x command [arguments]

The first form lists the active jobs. The options have the following meanings:

-l

List process IDs in addition to the normal information.

-n

Display information only about jobs that have changed status since the user was last notified of their status.

-p

List only the process ID of the job’s process group leader.

-r

Display only running jobs.

-s

Display only stopped jobs.

If jobspec is given, output is restricted to information about that job. If jobspec is not supplied, the status of all jobs is listed.

If the -x option is supplied, jobs replaces any jobspec found in command or arguments with the corresponding process group ID, and executes command, passing it arguments, returning its exit status.

kill ¶

kill [-s sigspec] [-n signum] [-sigspec] jobspec or pid
kill -l|-L [exit_status]

Send a signal specified by sigspec or signum to the process named by job specification jobspec or process ID pid. sigspec is either a case-insensitive signal name such as SIGINT (with or without the SIG prefix) or a signal number; signum is a signal number. If sigspec and signum are not present, SIGTERM is used. The -l option lists the signal names. If any arguments are supplied when -l is given, the names of the signals corresponding to the arguments are listed, and the return status is zero. exit_status is a number specifying a signal number or the exit status of a process terminated by a signal. The -L option is equivalent to -l. The return status is zero if at least one signal was successfully sent, or non-zero if an error occurs or an invalid option is encountered.

wait ¶

wait [-fn] [-p varname] [jobspec or pid …]

Wait until the child process specified by each process ID pid or job specification jobspec exits and return the exit status of the last command waited for. If a job spec is given, all processes in the job are waited for. If no arguments are given, wait waits for all running background jobs and the last-executed process substitution, if its process id is the same as $!, and the return status is zero. If the -n option is supplied, wait waits for a single job from the list of pids or jobspecs or, if no arguments are supplied, any job, to complete and returns its exit status. If none of the supplied arguments is a child of the shell, or if no arguments are supplied and the shell has no unwaited-for children, the exit status is 127. If the -p option is supplied, the process or job identifier of the job for which the exit status is returned is assigned to the variable varname named by the option argument. The variable will be unset initially, before any assignment. This is useful only when the -n option is supplied. Supplying the -f option, when job control is enabled, forces wait to wait for each pid or jobspec to terminate before returning its status, instead of returning when it changes status. If neither jobspec nor pid specifies an active child process of the shell, the return status is 127. If wait is interrupted by a signal, the return status will be greater than 128, as described above (see Signals). Otherwise, the return status is the exit status of the last process or job waited for.

disown ¶

disown [-ar] [-h] [jobspec … | pid … ]

Without options, remove each jobspec from the table of active jobs. If the -h option is given, the job is not removed from the table, but is marked so that SIGHUP is not sent to the job if the shell receives a SIGHUP. If jobspec is not present, and neither the -a nor the -r option is supplied, the current job is used. If no jobspec is supplied, the -a option means to remove or mark all jobs; the -r option without a jobspec argument restricts operation to running jobs.

suspend ¶

suspend [-f]

Suspend the execution of this shell until it receives a SIGCONT signal. A login shell, or a shell without job control enabled, cannot be suspended; the -f option can be used to override this and force the suspension. The return status is 0 unless the shell is a login shell or job control is not enabled and -f is not supplied.

When job control is not active, the kill and wait builtins do not accept jobspec arguments. They must be supplied process IDs.