The signal function in C language

• Signal is a system call that is a special kind of interrupt that is used to invoke a program when a particular "software break" occurs. Interrupts are typically special cases that occur during program execution, such as referencing an illegal address in special memory, and floating-point numbers are removed by 0.

• The prototype for signal () is:
  #include <signal．h>
void(*signal(int hum，void(*func)(int)))(int)；

• The int parameter in signal and its meaning
  SIGHUP 1 A terminal hangs or the control process terminates
  SIGINT 2 A Keyboard interrupt (if the break key is pressed)
  sigqu99v 3 C Keyboard exit key is pressed
  Sigill 4 C Illegal Instruction
  SIGABRT 6 C Exit instruction issued by abort (3)
  SIGFPE 8 C Floating-point exception
  SIGKILL 9 AEF Kill signal
  SIGSEGV-C Invalid memory reference
  Sigpipe a pipeline rupture: write a pipeline without a read port
  SIGALRM a signal sent by alarm (2)
  SIGTERM A Stop Signal
  SIGUSR1 30,10,16 A User-defined signal 1
  SIGUSR2 31,12,17 A user-defined signal 2
  SIGCHLD 20,17,18 B Sub-process end signal
  Sigcont 19,18,25 Process continues (a process that has been stopped)
  SIGSTOP 17,19,23 DEF Terminating process
  SIGTSTP 18,20,24 D Control Terminal (TTY) press the STOP key
  Sigttin 21,21,26 D Background process attempts to read from the control terminal
  Sigttou 22,22,27 D Background process attempts to write from the control terminal

The following signals are not listed in Posix.1, but are listed in SUSv2

Sigbus 10,7,10 C Bus error (bad memory access)
Sigpoll a Sys v-defined pollable event, synonymous with Sigio
Sigprof 27,27,29 A Profiling timer to
Sigsys,-, C Invalid system call (SVID)
SIGTRAP 5 C Trace/Breakpoint Capture
Sigurg 16,23,21 B Socket Emergency condition (4.2 BSD)
SIGVTALRM 26,26,28 A Real time alarm clock signal (4.2 BSD)
SIGXCPU 24,24,30 C exceeds the set CPU time limit (4.2 BSD)
Sigxfsz 25,25,31 C exceeds the set file size limit (4.2 BSD)

(For Sigsys,sigxcpu,sigxfsz, and the Sigbus,linux default action for some machine architectures is a (terminate), SUSv2 is C (Terminate and dump core).

Here are some other signals.

Signal value processing action causes the signal

Sigiot 6 C io capture instruction, synonymous with SIGABRT
SIGEMT 7,-, 7
Sigstkflt-,16,-A coprocessor Stack Error
SIGIO 23,29,22 A I/O operation is now available (4.2 BSD)
SIGCLD-,-, A and SIGCHLD synonymous
SIGPWR 29,30,19 A power failure (System V)
Siginfo,-,-A and SIGPWR synonymous
Siglost-,-,-A file lock is missing
Sigwinch 28,28,20 B window size change (4.3 BSD, Sun)
sigunused-,31,-A not used signal ('ll be Sigsys)

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Signal functions in the

C language