Analysis of Linux signals using

One, the linux signal

 1) SIGHUP   2) SIGINT   3) SIGQUIT  4) SIGILL   5) SIGTRAP
 6) SIGABRT  7) SIGBUS   8) SIGFPE   9) SIGKILL 10) SIGUSR1
11) SIGSEGV 12) SIGUSR2 13) SIGPIPE 14) SIGALRM 15) SIGTERM
16) SIGSTKFLT   17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP
21) SIGTTIN 22) SIGTTOU 23) SIGURG  24) SIGXCPU 25) SIGXFSZ
26) SIGVTALRM   27) SIGPROF 28) SIGWINCH    29) SIGIO   30) SIGPWR
31) SIGSYS  34) SIGRTMIN    35) SIGRTMIN+1  36) SIGRTMIN+2  37) SIGRTMIN+3
38) SIGRTMIN+4  39) SIGRTMIN+5  40) SIGRTMIN+6  41) SIGRTMIN+7  42) SIGRTMIN+8
43) SIGRTMIN+9  44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12 47) SIGRTMIN+13
48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14 51) SIGRTMAX-13 52) SIGRTMAX-12
53) SIGRTMAX-11 54) SIGRTMAX-10 55) SIGRTMAX-9  56) SIGRTMAX-8  57) SIGRTMAX-7
58) SIGRTMAX-6  59) SIGRTMAX-5  60) SIGRTMAX-4  61) SIGRTMAX-3  62) SIGRTMAX-2
63) SIGRTMAX-1  64) SIGRTMAX

1, the terminal button generates a signal

Ø Ctrl + c  → 2) SIGINT（终止/中断）     "INT" ----Interrupt
Ø Ctrl + \  → 3) SIGQUIT（退出）    
Ø Ctrl + z  → 20) SIGTSTP（暂停/停止）  "T" ----Terminal 终端。

2, the hardware abnormality generates a signal

Ø 总线错误      → 7) SIGBUS
Ø 除0操作      → 8) SIGFPE (浮点数例外)    "F" -----float 浮点数。
Ø 非法访问内存  → 11) SIGSEGV (段错误)

3, List of Linux regular signals

2
(SIGINT),
3(SIGQUIT),
6(SIGABRT),
9(SIGKILL),
11(SIGSEGV),
14(SIGALRM),
17(SIGCHLD),
19(SIGSTOP),
20(SIGTSTP) signals to remember

serial number	Signal	corresponding event	default action
1	SIGHUP	When the user exits the shell, all processes started by that shell will receive this signal	kill process
2	SIGINT	When the user presses a key combination, the user terminal sends this signal to the running program started by the terminal	kill process
3	SO MUCH	This signal is generated when the user presses a key combination, and the user terminal sends some signals to the running program started by the terminal	kill process
4	SEAL	The CPU detects that a process has executed an illegal instruction	Terminate the process and generate the core file
5	SIGTRAP	This signal is generated by a breakpoint instruction or other trap instruction	Terminate the process and generate the core file
6	SIGABRT	This signal is generated when the abort function is called	Terminate the process and generate the core file
7	SIGBUS	Illegal access to memory addresses, including memory alignment errors	Terminate the process and generate the core file
8	SIGFPE	Emitted when a fatal arithmetic error occurs. Not only floating point arithmetic errors, but also all arithmetic errors such as overflow and division by 0	Terminate the process and generate the core file
9	SIGKILL	Terminate the process unconditionally. This signal cannot be ignored, handled and blocked	kill process, any process can be killed
10	SIGUSE1	User-defined signal. That is, the programmer can define and use the signal in the program	kill process
11	SIGSEGV	Indicates that the process made an invalid memory access (segmentation fault)	Terminate the process and generate the core file
12	SIGUSR2	Another user-defined signal that the programmer can define and use in the program	kill process
13	SIGPIPE	Broken pipe writes data to a pipe without a read end	kill process
14	SIGALRM	The timer times out, the time out is set by the system call alarm	kill process
15	SIGTERM	Program end signal. Unlike SIGKILL, this signal can be blocked and terminated. Usually used to indicate that the program exits normally. When executing the shell command Kill, this signal is generated by default	kill process
16	SIGSTKFLT	Signals that appeared in early versions of Linux,	Backward compatibility remains
17	SIGCHLD	When the child process ends, the parent process will receive this signal	ignore this signal
18	SIGCONT	If the process is stopped, keep it running	continue/ignore.
19	SIGSTOP	Stop the execution of the process. Signals cannot be ignored, handled and blocked	to terminate the process
20	SIGTSTP	Stop the terminal interactive process from running. This signal is emitted when a key combination is pressed	Pause the process
21	SIGTTIN	Background process reading terminal console	Pause the process
22	SIGTTOU	This signal is similar to SIGTTIN and occurs when a background process wants to output data to the terminal	Pause the process
23	SIGURG	When there is urgent data on the socket, send some signals to the currently running process to report that urgent data has arrived. As network out-of-band data arrives	ignore this signal
24	SIGXCPU	The process execution time exceeds the CPU time allocated to the process, the system generates the signal and sends it to the process	kill process
25	SIGXFSZ	Exceeds the file's maximum length setting	kill process
26	SIGVTALRM	This signal is generated when the virtual clock times out. Similar to SIGALRM, but this signal only counts the CPU usage time of the process	kill process
27	SGIPROF	Similar to SIGVTALRM, it does not include the CPU time spent by the process and the execution time of system calls	kill process
28	SIGWINCH	Emitted when the window is resized	ignore this signal
29	SIGIO	This signal indicates to the process that an asynchronous IO event was issued	ignore this signal
30	SIGPWR	shutdown	kill process
31	SIGSYS	invalid system call	Terminate the process and generate the core file
34~64	SIGRTMIN ～ SIGRTMAX	LINUX real-time signals, they have no fixed meaning (can be customized by the user)	kill process

Second, the use of the registered signal signal function

Prototype of the function:

#include <signal.h>

       typedef void (*sighandler_t)(int);

       sighandler_t signal(int signum, sighandler_t handler);