The specific meaning of the relevant signal in PHP operation process

Sigquit establish core file termination process, and generate core file
Sigill Creating a core file illegal directive
SIGTRAP build core file tracking self-trapping
Sigbus establishing a core file bus error
SIGSEGV creating core file Segment Illegal error
SIGFPE creating a core file floating point exception
Sigiot creating a core file to perform I/O self-trapping

sigstop    stop process      stop signal from non-terminal
sigtstp    stop process        stop signal from terminal
sigttou    stop process      background process write terminal
sigttin     Stop process       background process read Terminal

sighup     Terminate process      terminal line hangs
sigint     terminate process      Interrupt Process
sigxgpu    terminate process      CPU time-out
sigxfsz     Terminate process      file length too long
sigprof    terminate process      Statistics distribution graph with timer to time
sigusr1    terminate process       user-defined signal 1
sigusr2    Terminate process      user-defined signal 2
sigvtalrm  Terminate process      virtual timer up to
sigkill     Terminate process      kill process
sigpipe    terminate process       Write data to a pipeline without a read process
sigalarm   terminate process      timer to
sigterm    terminate process        Software termination signal

Sigcont ignore signal continue execution of a stopped process
Sigurg ignoring signal I/O emergency signal
SIGIO ignoring the signal descriptor can be I/O
SIGCHLD Ignore signal Notify parent process when child process stops or exits
Sigwinch ignoring signal window size changes

1 SIGHUP

This signal in the user terminal connection (normal or abnormal, at the end of the issue, usually at the end of the terminal control process to notify the same session of the various jobs, then they are no longer associated with the control terminal.

2, SIGINT

program termination (interrupt, signal, emitted when the user types Intr characters (usually ctrl-c,

3, Sigquit

Sigquit and SIGINT are similar, but are controlled by the Quit character (usually Ctrl-S). The process generates a core file in the sense that the sigquit exits, similar to a program error signal.

4, Sigill

Sigill executed an illegal instruction. This is usually due to an error in the executable file itself or an attempt to execute a data segment. This signal can also be generated when a stack overflows.

5, SIGTRAP

The SIGTRAP is generated by a breakpoint instruction or other trap instruction. Used by debugger.

6, SIGABRT

The SIGABRT program itself discovers the error and calls abort when it is generated.
6, Sigiot

The Sigiot is generated on the PDP-11 by the IoT instructions, on other machines and SIGABRT.

7, Sigbus

Sigbus illegal address, including memory address alignment (alignment, error. Eg: accesses an integer of four word lengths, but whose address is not a multiple of 4.

8, SIGFPE

SIGFPE is emitted when a fatal arithmetic operation error occurs. This includes not only floating-point arithmetic errors, but also all other arithmetic errors such as overflow and divisor 0.

9, SIGKILL

The SIGKILL is used to immediately end the run of the program. This signal cannot be blocked, processed and ignored.

10, SIGUSR1

SIGUSR1 left for users to use

11, SIGSEGV

SIGSEGV attempts to access memory that is not allocated to itself, or attempts to write data to a memory address that does not have write permissions.

12, SIGUSR2

SIGUSR2 left for users to use

13, Sigpipe

Broken pipe

14, SIGALRM

The SIGALRM clock timing signal calculates the actual time or clock time. The alarm function uses this signal.

15, SIGTERM

SIGTERM program End (terminate, signal, unlike Sigkill, the signal can be blocked and processed. Usually used to ask the program to exit normally. Shell command

Kill generates this signal by default.

17, SIGCHLD

At the end of the SIGCHLD child process, the parent process receives this signal.

18, Sigcont

Sigcont let a stop (stopped, the process continues execution. This signal cannot be blocked. You can use a handler to get the program to do certain work when it changes from the stopped state to the execution. For example, to re-display the prompt

19, SIGSTOP

SIGSTOP Stop (Stopped, the execution of the process. Note the difference between it and terminate and interrupt: The process is not over yet, just pausing execution. This signal cannot be blocked, processed or ignored.

20, SIGTSTP

SIGTSTP stops the process from running, but the signal can be processed and ignored. When a user types Susp characters (usually ctrl-z, this signal is emitted

21, Sigttin

Sigttin when a background job wants to read data from a user terminal, all processes in that job receive a sigttin signal. By default, these processes stop executing.

22, Sigttou

Sigttou is similar to Sigttin, but is received when writing terminal (or modifying terminal mode).

23, Sigurg

Sigurg is generated when "emergency" data or Out-of-band data arrives at the socket.

24, Sigxcpu

SIGXCPU exceeds CPU time resource limit. This limit can be read/changed by Getrlimit/setrlimit.

25, Sigxfsz

Sigxfsz exceeds the file size resource limit.

26, Sigvtalrm

SIGVTALRM virtual clock signal. is similar to SIGALRM, but calculates the CPU time that is consumed by the process.

27, Sigprof

Sigprof is similar to SIGALRM/SIGVTALRM, but includes the CPU time used by the process and the time of the system call.

28, Sigwinch

Sigwinch when the window size changes.

29, SIGIO

The SIGIO file descriptor is ready to start the input/output operation.

30, SIGPWR

SIGPWR Power Failure

There are two signals to stop a process: Sigterm and Sigkill. Sigterm is friendly and the process captures the signal and shuts down the program according to your needs. Before you close the program, you can end the open record file and complete the task you are doing. In some cases, if the process is working and cannot be interrupted, the process can ignore the sigterm signal.

For Sigkill signals, the process cannot be ignored. This is a "I don't care what you are doing, stop immediately" signal. If you send a sigkill signal to the process, Linux stops the process there.

The specific meaning of the relevant signal in PHP operation process