Process.kill

Sends a signal to each process specified by ids (which must specify at least one ID); returns the count of signals sent.

For each given id, if id is:

• Positive, sends the signal to the process whose process ID is id.

• Zero, send the signal to all processes in the current process group.

• Negative, sends the signal to a system-dependent collection of processes.

Argument signal specifies the signal to be sent; the argument may be:

• An integer signal number: e.g., -29, 0, 29.

• A signal name (string), with or without leading 'SIG', and with or without a further prefixed minus sign ('-'): e.g.:

  • 'SIGPOLL'.

  • 'POLL',

  • '-SIGPOLL'.

  • '-POLL'.

• A signal symbol, with or without leading 'SIG', and with or without a further prefixed minus sign ('-'): e.g.:

  • :SIGPOLL.

  • :POLL.

  • :'-SIGPOLL'.

  • :'-POLL'.

If signal is:

• A non-negative integer, or a signal name or symbol without prefixed '-', each process with process ID id is signalled.

• A negative integer, or a signal name or symbol with prefixed '-', each process group with group ID id is signalled.

Use method Signal.list to see which signals are supported by Ruby on the underlying platform; the method returns a hash of the string names and non-negative integer values of the supported signals. The size and content of the returned hash varies widely among platforms.

Additionally, signal 0 is useful to determine if the process exists.

Example:

pid = fork do
  Signal.trap('HUP') { puts 'Ouch!'; exit }
  # ... do some work ...
end
# ...
Process.kill('HUP', pid)
Process.wait

Output:

Ouch!

Exceptions:

• Raises Errno::EINVAL or RangeError if signal is an integer but invalid.

• Raises ArgumentError if signal is a string or symbol but invalid.

• Raises Errno::ESRCH or RangeError if one of ids is invalid.

• Raises Errno::EPERM if needed permissions are not in force.

In the last two cases, signals may have been sent to some processes.