Linux Signal List

Linux Signal Table

Linux supports POSIX standard signals and real-time signals. Below is a brief summary of the Linux signal, with detailed details to see Man 7 signal.

The default action has the following meanings:

term termination process

Signal	Take value	Default action	Meaning (the cause of the signal)
SIGHUP	1	Term	Terminal hangs or process death
SIGINT	2	Term	Interrupt signal from the keyboard
Sigquit	3	Core	Departure signal from the keyboard
Sigill	4	Core	Illegal instructions
Sigabrt	6	Core	Abnormal signal from abort
SIGFPE	8	Core	Floating-point exceptions
SIGKILL	9	Term	Kill
SIGSEGV	11	Core	Segment illegal error (invalid memory reference)
Sigpipe	13	Term	Pipeline corruption: Write data to a pipeline that does not have a read process
Sigalrm	14	Term	Timer-to-time signal from alarm
SIGTERM	15	Term	Terminate
SIGUSR1	30,10,16	Term	User-defined Signal 1
SIGUSR2	31,12,17	Term	User-defined Signal 2
SIGCHLD	20,17,18	Ign	Child process stopped or terminated
Sigcont	19,18,25	Cont	If stopped, continue execution
SIGSTOP	17,19,23	Stop	Stop signal not from the terminal
Sigtstp	18,20,24	Stop	Stop signal from the terminal
Sigttin	21,21,26	Stop	Background process Read Terminal
Sigttou	22,22,27	Stop	Background Process Write Terminal
Sigbus	10,7,10	Core	Bus Error (Memory access error)
Sigpoll		Term	Pollable event Occurrence (Sys V), synonymous with Sigio
Sigprof	27,27,29	Term	Statistical distribution chart with timers to the time
Sigsys	,-, 12	Core	Illegal system call (SVR4)
SIGTRAP	5	Core	Trace/Breakpoint Self-trapping
Sigurg	16,23,21	Ign	Socket emergency signal (4.2BSD)
Sigvtalrm	26,26,28	Term	Virtual timer to time (4.2BSD)
Sigxcpu	24,24,30	Core	CPU Time Exceeded (4.2BSD)
Sigxfsz	25,25,31	Core	File length limit exceeded (4.2BSD)
Sigiot	6	Core	IoT self-trapping, synonymous with SIGABRT
Sigemt	7,-, 7		Term
Sigstkflt	-,16,-	Term	Coprocessor stack error (not used)
SIGIO	23,29,22	Term	I/O can be performed on a descriptor
Sigcld	-,-, 18	Ign	Synonymous with SIGCHLD
Sigpwr	29,30,19	Term	Power failure (System V)
Siginfo	,-,-		Synonymous with SIGPWR
Siglost	-,-,-	Term	File Lock missing
Sigwinch	28,28,20	Ign	Window size Change (4.3BSD, Sun)
Sigunused	-,31,-	Term	Signal not used (would be sigsys)

Description

Some of the values of the signals are hardware-related (General Alpha and SPARC architectures with the first value, i386, PPC, and SH schemas with intermediate values, the MIPS schema with a third value, which indicates that the value of the corresponding schema is unknown).

The blue is the posix.1-1990 standard signal.

Sigkill and Sigstop signals cannot be hooked, blocked, or ignored.

Cyan is the signal defined by SUSV2 and posix.1-2001.

Prior to the Linux 2.2 (including) kernel, the default action for Sigsys, SIGXCPU, Sigxfsz, and Sigbus (except for SPARC and MIPS architectures) was to terminate the process, but without core dump. Linux 2.4 follows the posix.1-2001 requirements, and the default action for these signals is changed to: terminate the process and do core dump at the same time.

Orange is the other common signal.

The Signal 29 is SIGINFO/SIGPWR on Alpha and siglost on SPARC.

SIGEMT is not described in posix.1-2001, but is still visible in most unices, the typical default action is to terminate the process and do the core dump.

SIGPWR is not described in posix.1-2001, the typical default action in some unices that use it is to ignore.

Sigio is not described in posix.1-2001, the typical default action in some unices that use it is to ignore.

Processes can change the default processing of signals by using sigaction and signal system calls (using the signal is poor portability). The process can choose one of the following 3 signal processing methods:

1, perform the default operation;

2, ignoring the signal;

3. Captures the signal, but invokes the custom handler function through the signal handle.

The signal may be blocked. Each thread in the process has a separate signal mask to indicate that the signal for this thread is blocked. The thread uses the Pthread_sigmask to set its signal mask. Single-threaded programs can use Sigprocmask to manipulate signal masks. In a multithreaded program, the default behavior for all threads to handle a specified signal is the same.

Linux Signal List