signals

Introduction

Signals are used to interact between processes and can occur at anytime, typically they are kill signals however processes can opt to handle them programatically unless they are SIGKILL or SIGSTOP signals.

List Of Available Signals

Table of signals

SIGNAL	VALUE	DEFAULT ACTION	POSIX?	MEANING
SIGHUP	1	Terminate	Yes	Hangup detected on controlling terminal or death of controlling process
SIGINT	2	Terminate	Yes	Interrupt from keyboard
SIGQUIT	3	Core dump	Yes	Quit from keyboard
SIGILL	4	Core dump	Yes	Illegal instruction
SIGTRAP	5	Core dump	No	Trace/breakpoint trap for debugging
SIGABTR SIGIOT	6	Core dump	Yes	Abnormal termination
SIGBUS	7	Core dump	Yes	Bus error
SIGFPE	8	Core dump	Yes	Floating point exception
SIGKILL	9	Terminate	Yes	Kill signal (cannot be caught or ignored)
SIGUSR1	10	Terminate	Yes	User-defined signal 1
SIGSEGV	11	Core dump	Yes	Invalid memory reference
SIGUSR2	12	Terminate	Yes	User-defined signal 2
SIGPIPE	13	Terminate	Yes	Broken pipe: write to pipe with no readers
SIGALRM	14	Terminate	Yes	Timer signal from alarm
SIGTERM	15	Terminate	Yes	Process termination
SIGSTKFLT	16	Terminate	No	Stack fault on math co-processor
SIGCHLD	17	Ignore	Yes	Child stopped or terminated
SIGCONT	18	Continue	Yes	Continue if stopped
SIGSTOP	19	Stop	Yes	Stop process (can not be caught or ignored)
SIGTSTP	20	Stop	Yes	Stop types at tty
SIGTTIN	21	Stop	Yes	Background process requires tty input
SIGTTOU	22	Stop	Yes	Background process requires tty output
SIGURG	23	Ignore	No	Urgent condition on socket (4.2 BSD)
SIGXCPU	24	Core dump	Yes	CPU time limit exceeded (4.2 BSD)
SIGXFSZ	25	Core dump	Yes	File size limit exceeded (4.2 BSD)
SIGVTALRM	26	Terminate	No	Virtual alarm clock (4.2 BSD)
SIGPROF	27	Terminate	No	Profile alarm clock (4.2 BSD)
SIGWINCH	28	Ignore	No	Window resize signal (4.3 BSD, Sun)
SIGIO SIGPOLL	29	Terminate	No	I/O now possible (4.2 BSD) (System V)
SIGPWR	30	Terminate	No	Power Failure (System V)
SIGSYS SIGUNUSED	31	Terminate	No	Bad System Called. Unused signal