sigint

Trap commandtarpThe command is used to perform the action after the specified signal is received, usually in order to complete the cleanup when the shell script is interrupted. For example:When the script is pressed at execution time CTRL+c , "program exit ..." is displayed and exits ( CTRL+c the signal is SIGINT)#!/bin/bashtrap "ehco ‘program exit...‘; exit 2" SIGINT....SignalCommon signals

file sharing/printing service snmpd: Local simple network governance process squid: Activate the proxy server squidsyslog: A script XFS: X Window server that enables Syslog and klogd system logs to wait for processes during system boot, providing xntpd: Network Time Server ypbind for local and remote X servers: activate ypbind service process yppasswdd: NIS Password server ypserv: NIS master server GPM: mouse-over identd: AUTH service for NIS (Network Information System) clients, similar to fin

$ kill -l1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE9) SIGKILL 10) SIGUSR1 11) SIGSEGV 12) SIGUSR213) SIGPIPE 14) SIGALRM 15) SIGTERM 16) SIGSTKFLT 17) SIGCHLD18) SIGCONT 19) SIGSTOP 20) SIGTSTP 21) SIGTTIN22) SIGTTOU 23) SIGURG 24) SIGXCPU 25) SIGXFSZ26) SIGVTALRM 27) SIGPROF 28) SIGWINCH 29) SIGIO30) SIGPWR 31) SIGSYS

program must run on a non-POSIX System) Set a new signal processing function act for the signal SIGNUM, and retain the original signal processing function oldact of the signal.Int sigaction (INT signo, const struct sigaction * restrict act, Struct sigaction * restrict oact ); The sigaction function is used to change the SIGINT interrupt signal and Use Act. sa_handler to switch to the new operation. The structure sigaction is defined as follows:Struct

default behaviorSignal Processing Experiment Program:1#include 2#include 3#include 4 5 voidOuchintSig//define the Ouch function and process the signal when the signal is intercepted6 {7printf"ouch!-I got signal%d\n", SIG);//print a word first8(void) signal (SIGINT, SIG_DFL);//then, the general SIGINT signal generated by the CTRL + C to return to the default form of processing9 }Ten One intMain () A { -(vo

process 1th, and process 1th becomes the stepfather of those processes. Process 1th will handle the resources of these processes well, and when they end, process 1th will automatically reclaim resources. So, another temporary way to deal with zombie processes is to close their parent processes.4. SignalThe general multi-process thing is that the above is over, but the signal is really a very important thing in the system. The signal is the semaphore, light a signal, the program will react. You

signal.In addition, the application can set a default handler for a signal through functions such as signal (). For example, when the user presses CTRL + C, the shell emits a SIGINT signal, and the default handler for SIGINT is the exit code that executes the process, but the following example sets the SIGINT response function to Int_handler.[Plain]View PlainCop

Signal ListSIGABRT process stops running 6sigalrm warning Clock SIGFPE computation exception sighup system hangs Sigill illegal instruction SIGINT Terminal Interrupt 2 SIGKILL Stop process (this signal cannot be ignored or captured) Sigpipe writes data to a pipe that is not read SIGSEGV invalid memory segment access Sigqout terminal exits 3 SIGTERM terminating SI

I. SignalWe run a program under the shell, can be in the process is running when the keyboard input CTRL + C, you will see that the process has been terminated, in fact, when we type CTRL + C is to send a SIGINT signal to the process, When a hardware interrupt occurs, the system will switch from executing the code to the kernel to handle the signal, while the default processing action of this signal is to terminate the process, so the running process

; sigaction (SIGTERM, act,0) ||0> sigaction (SIGINT, act,0) ||0> sigaction (SIGUSR1, act,0) ||0> sigaction (SIGUSR2, act,0) ||0> sigaction (SIGCHLD, act,0) ||0> sigaction (sigquit, act,0) {zlog (Zlog_syserror,"failed to init signals:sigaction ()"); return-1; } return 0;}The master process registered Sigterm,sigint,sigusr1,sigusr2,sigchld,sigquit and created Socketpair sp[]. When these signals are re

automatically reclaim resources. So, another temporary way to deal with zombie processes is to close their parent processes.4. SignalThe general multi-process thing is that the above is over, but the signal is really a very important thing in the system. The signal is the semaphore, light a signal, the program will react. You must have used this, for example, to run a program under the terminal, waiting for a half-day of no response, you may press CTRL + C to close the program. In fact, this is

time also no response, you may press CTRL + C to close the program. In fact, this is where the keyboard sends an interrupt signal to the program: SIGINT. Sometimes the process loses its response and executes the kill [PID] command, and the program receives a SIGTERM signal without any additional parameters. Is it possible to change the default behavior when the program receives the two signals above and ends the execution by default? Must be able to

); Sigaction (SIGINT, sa_ignore, sa_intr); 2. Ignore SIGINT signal sigaction (Sigquit, sa_ignore, sa_quit); 3. Ignore sigquit signal switch (PID = fork ()) {case-1: return-1; Case 0:sigaction (SIGINT, sa_intr, NULL); Sigaction (Sigquit, sa_quit, NULL); Sigprocmask (Sig_setmask, orig_mask,

1. Signals are soft interrupts that provide a mechanism for handling asynchronous eventsAn asynchronous event can originate from outside the system (for example, user input ctrl-c) or from within the system (for example, except 0) the kernel uses one of the following three methods to process the signal: (1)Ignore this signal。Sigkill and Sigstop cannot be ignored。 (2)capture and process the signal。 The kernel would suspend execution of the process ' s current code path and jump to a previously re

signal does not terminate the program, Sigsuspend () returns 1, and the errno is set to Eintr. Special Reminder : If a signal is blocked by the process, it will not be passed to the process, but will stay in the pending state, when the process is de-processing signal blocking, the pending signal will be processed immediately. Here is an example to illustrate the use of the above function, the source file is sigset.c, the code is as follows:#include The results of the operation are

NULL; } }; TestServer G_server; void StopService () { G_server. Stop (); } void StartService () { G_server. Start (); G_server. Wait (); } void Signalhandler (int sig) { Switch (SIG) { Case SIGINT: StopService (); Default Break } } int main (int argc, char* argv[]) { Signal (SIGINT, Signalhandler); StartService (); return 0; } This code describes a simple service p

What's the difference between Nohup and ? Many students have responded, but not all of the students understand all right, today to dig their own pits to fill out.The test code is as follows:is a dead loop program that outputs hello and the number of loops, and sleeps for 1 seconds per output line.What is the effect of using the./a.out foreground running program?The program outputs a string at the terminal every second.At this point, if you type CTRL + C, the program receives a

Clean up temporary files You can use trap commands to capture signals, and trap capture signals in the shell are equivalent to signal or sigaction in C or most other languages.One of the most common scenarios for a trap is to clean up temporary files when expected exits and unexpected exits.Unfortunately there are not many shell scripts to do so. #!/bin/sh# Make a cleanup functionCleanup () {RM--force--"${tmp}"}# Trap The Special "EXIT" group, which is always run when the shell exits.Trap Clea

A signal (signal) is a software interrupt that provides a way to handle asynchronous events and is the only asynchronous communication between processes. In a Linux system, the subsequent signaling mechanism is extended according to the POSIX standard, which can be used to inform not only what happened to a program, but also the process of passing data to it.First, the source of the signalThe source of the signal can have many kinds of test, according to the different conditions can be divided i

it is interrupted. #include 2.3 signals that have been sent but not yet received are called pending signals . The system uses a vector to represent the set of signals to be processed, so there is at most one pending signal for each type of signal. A pending signal can be received at most once. 3. Signal Processingsome problems caused by 3.1 signal processing:A) The pending signal is blocked : If the program is processing SIGINT, then a