— Scheme Procedure: kill pid sig
— C Function: scm_kill (pid, sig)

Send the signal sig to the specified process or group of processes.

pid specifies the processes to which the signal is sent:

pid greater than 0

The process whose identifier is pid.

pid equal to 0

All processes in the current process group.

pid less than -1

The process group whose identifier is -pid

pid equal to -1

If the process is privileged, all processes except for some special system processes. Otherwise, all processes with the current effective user ID.

sig should be specified using a variable corresponding to the Unix symbolic name, e.g.,

— Variable: SIGHUP

Hang-up signal.

— Variable: SIGINT

Interrupt signal.

— Scheme Procedure: raise sig
— C Function: scm_raise (sig)

Send the specified signal sig to the current process, where sig is as described for the kill procedure.

— Scheme Procedure: sigaction signum [action [flags]]
— C Function: scm_sigaction (signum, action, flags)

Install or report the signal handler for a specified signal.

signum is the signal number, which can be specified using the value of variables such as SIGINT.

If action is omitted, sigaction returns a pair: The car is the current signal hander, which will be either an integer with the value SIG_DFL (default action) or SIG_IGN (ignore), or the Scheme procedure which handles the signal, or #f if a non-Scheme procedure handles the signal. The cdr contains the current sigaction flags for the handler.

If action is provided, it is installed as the new handler for signum. action can be a Scheme procedure taking one argument, or the value of SIG_DFL (default action) or SIG_IGN (ignore), or #f to restore whatever signal handler was installed before sigaction was first used. Optional third arg flags can be specified for the new handler (SA_RESTART will always be added if it's available and the system is using restartable system calls). The return value is a pair with information about the old handler as described above.

This interface does not provide access to the "signal blocking" facility. Maybe this is not needed, since the thread support may provide solutions to the problem of consistent access to data structures.

— Scheme Procedure: restore-signals
— C Function: scm_restore_signals ()

Return all signal handlers to the values they had before any call to sigaction was made.

— Scheme Procedure: alarm i
— C Function: scm_alarm (i)

Set a timer to raise a SIGALRM signal after the specified number of seconds (an integer). It's advisable to install a signal handler for SIGALRM beforehand, since the default action is to terminate the process.

The return value indicates the time remaining for the previous alarm, if any. The new value replaces the previous alarm. If there was no previous alarm, return zero.

— Scheme Procedure: pause
— C Function: scm_pause ()

Pause the current process (thread?) until a signal arrives whose action is to either terminate the current process or invoke a handler procedure.

— Scheme Procedure: sleep i
— C Function: scm_sleep (i)

Wait for i seconds (an integer) or until a signal arrives. The return value is zero if the time elapses or the number of seconds remaining otherwise.

— Scheme Procedure: usleep i
— C Function: scm_usleep (i)

Sleep for i microseconds. If no (unblocked) signals arrive during this time, return 0 (zero), otherwise, the number of microseconds remaining (useful for a subsequent call to usleep).