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(zsh.info)Jobs & Signals

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Jobs & Signals
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Jobs
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If the MONITOR option is set, an interactive shell associates a _job_
with each pipeline.  It keeps a table of current jobs, printed by the
jobs command, and assigns them small integer numbers.  When a job is
started asynchronously with `&', the shell prints a line which looks
like:

     [1] 1234

indicating that the job which was started asynchronously was job number
1 and had one (top-level) process, whose process ID was 1234.

If a job is started with `&|' or `&!', then that job is immediately
disowned.  After startup, it does not have a place in the job table,
and is not subject to the job control features described here.

If you are running a job and wish to do something else you may hit the
key ^Z (control-Z) which sends a TSTP signal to the current job:  this
key may be redefined by the susp option of the external stty command.
The shell will then normally indicate that the job has been `suspended',
and print another prompt.  You can then manipulate the state of this
job, putting it in the background with the bg command, or run some other
commands and then eventually bring the job back into the foreground with
the foreground command fg.  A ^Z takes effect immediately and is like
an interrupt in that pending output and unread input are discarded when
it is typed.

A job being run in the background will suspend if it tries to read from
the terminal.  Background jobs are normally allowed to produce output,
but this can be disabled by giving the command `stty tostop'.  If you
set this tty option, then background jobs will suspend when they try to
produce output like they do when they try to read input.

When a command is suspended and continued later with the fg or wait
builtins, zsh restores tty modes that were in effect when it was
suspended.  This (intentionally) does not apply if the command is
continued via `kill -CONT', nor when it is continued with bg.

There are several ways to refer to jobs in the shell.  A job can be
referred to by the process ID of any process of the job or by one of
the following:

%NUMBER
     The job with the given number.

%STRING
     Any job whose command line begins with STRING.

%?STRING
     Any job whose command line contains STRING.

%%
     Current job.

%+
     Equivalent to `%%'.

%-
     Previous job.

The shell learns immediately whenever a process changes state.  It
normally informs you whenever a job becomes blocked so that no further
progress is possible.  If the NOTIFY option is not set, it waits until
just before it prints a prompt before it informs you.

When the monitor mode is on, each background job that completes
triggers any trap set for CHLD.

When you try to leave the shell while jobs are running or suspended,
you will be warned that `You have suspended (running) jobs'.  You may
use the jobs command to see what they are.  If you do this or
immediately try to exit again, the shell will not warn you a second
time; the suspended jobs will be terminated, and the running jobs will
be sent a SIGHUP signal, if the HUP option is set.

To avoid having the shell terminate the running jobs, either use the
`nohup' command (see man page nohup(1)) or the disown builtin.

Signals
=======

The INT and QUIT signals for an invoked command are ignored if the
command is followed by `&' and the MONITOR option is not active.
Otherwise, signals have the values inherited by the shell from its
parent (but see the TRAPNAL special functions in Note: Functions).