coreutils: kill invocation

1 
1 24.1 ‘kill’: Send a signal to processes
1 =======================================
1 
1 The ‘kill’ command sends a signal to processes, causing them to
1 terminate or otherwise act upon receiving the signal in some way.
1 Alternatively, it lists information about signals.  Synopses:
1 
1      kill [-s SIGNAL | --signal SIGNAL | -SIGNAL] PID...
1      kill [-l | --list | -t | --table] [SIGNAL]...
1 
1    Due to shell aliases and built-in ‘kill’ functions, using an
1 unadorned ‘kill’ interactively or in a script may get you different
1 functionality than that described here.  Invoke it via ‘env’ (i.e., ‘env
1 kill ...’) to avoid interference from the shell.
1 
1    The first form of the ‘kill’ command sends a signal to all PID
1 arguments.  The default signal to send if none is specified is ‘TERM’.
1 The special signal number ‘0’ does not denote a valid signal, but can be
1 used to test whether the PID arguments specify processes to which a
1 signal could be sent.
1 
1    If PID is positive, the signal is sent to the process with the
1 process ID PID.  If PID is zero, the signal is sent to all processes in
1 the process group of the current process.  If PID is −1, the signal is
1 sent to all processes for which the user has permission to send a
1 signal.  If PID is less than −1, the signal is sent to all processes in
1 the process group that equals the absolute value of PID.
1 
1    If PID is not positive, a system-dependent set of system processes is
1 excluded from the list of processes to which the signal is sent.
1 
1    If a negative PID argument is desired as the first one, it should be
1 preceded by ‘--’.  However, as a common extension to POSIX, ‘--’ is not
1 required with ‘kill -SIGNAL -PID’.  The following commands are
1 equivalent:
1 
1      kill -15 -1
1      kill -TERM -1
1      kill -s TERM -- -1
1      kill -- -1
1 
1    The first form of the ‘kill’ command succeeds if every PID argument
1 specifies at least one process that the signal was sent to.
1 
1    The second form of the ‘kill’ command lists signal information.
1 Either the ‘-l’ or ‘--list’ option, or the ‘-t’ or ‘--table’ option must
1 be specified.  Without any SIGNAL argument, all supported signals are
1 listed.  The output of ‘-l’ or ‘--list’ is a list of the signal names,
1 one per line; if SIGNAL is already a name, the signal number is printed
1 instead.  The output of ‘-t’ or ‘--table’ is a table of signal numbers,
1 names, and descriptions.  This form of the ‘kill’ command succeeds if
1 all SIGNAL arguments are valid and if there is no output error.
1 
1    The ‘kill’ command also supports the ‘--help’ and ‘--version’
1 options.  ⇒Common options.
1 
1    A SIGNAL may be a signal name like ‘HUP’, or a signal number like
1 ‘1’, or an exit status of a process terminated by the signal.  A signal
1 name can be given in canonical form or prefixed by ‘SIG’.  The case of
1 the letters is ignored, except for the ‘-SIGNAL’ option which must use
11 upper case to avoid ambiguity with lower case option letters.  ⇒
 Signal specifications, for a list of supported signal names and
1 numbers.
1