Process termination methods

Overview & #160; & #160; & #160; exit normally & #160; & #160; & #160; & #160; & #160; & #160; & #160; & #160; & #160; & #160; & #160; return [return] & #160; & #160; & #160; & #; from the main function; & #160; & #160; & #160; & #160; & #160; & #1 overview

Exit normally

Returns [return] from the main function.

CALL exit

Call _ exit

Exit unexpectedly

Call abort to generate a SIGABOUT signal

End by signal Ctrl + c [SIGINT]

Test [exit/_ exit]

// Try to view the print output of the program # include
 
  
# Include
  
   
# Include
   
    
Using namespace std; int main () {cout <"In main, pid =" <getpid (); // remove endl; // principle: associate with the terminal, stdout is a row buffer. in a file, it is a full buffer. // For details, refer to the relevant section of Advanced Programming in UNIX environment // exit (0); it is a C library function, explanation: _ exit (0 );}
   
  
 

As shown in the figure, the system call _ exit directly falls into the kernel, while the C language library function is through a series of system cleanup work, and then calls the Linux kernel

Int main () {cout <"In main, pid =" <getpid (); fflush (stdout); // added the buffer refresh work_exit (0 );}

 

Summary differences between exit and _ exit

1) _ exit is a system call, and exit is a c-library function.

2) exit will clear the I/O cache

3) exit will execute a call to terminate the processing program // terminate the processing program as follows

 

Terminate the processing program: atexit

       #include 
 
         int atexit(void (*function)(void));
 

Test procedure:

Void exitHandler1 (void) {cout <"If exit with exit, the function exitHandler will be called1" <endl;} void exitHandler2 (void) {cout <"If exit with exit, the function exitHandler will be called2" <endl;} int main () {cout <"In main, pid = "<getpid () <endl; atexit (exitHandler1); // note that after registration, execute atexit (exitHandler2); exit (0 );}

Exceptional termination

void exitHandler1(void){    cout << "If exit with exit, the function exitHandler will be called1" << endl;}void exitHandler2(void){    cout << "If exit with exit, the function exitHandler will be called2" << endl;} int main(){    cout << "In main, pid = " << getpid() << endl;    atexit(exitHandler1);    atexit(exitHandler2);    abort();    //exit(0);}