Which function is used in C++ stdlib to exit from program execution with status code?
In Java, there's:
System.exit(0)
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3 Answers
Assuming you only have one thread:
#include <iostream>
int main()
{
std::cout << "Hello, World!\n";
return(0);
// PROGRAM ENDS HERE.
std::cout << "You should not see this.\n";
return(0);
}
Output:
Hello, World!
The return(0); can be placed anywhere you like - it'll end int main(), and hence your program.
Alternatively, you can call exit(EXIT_SUCCESS); or exit(EXIT_FAILURE); from anywhere you like:
/* exit example */
#include <stdio.h>
#include <stdlib.h>
int main ()
{
FILE * pFile;
pFile = fopen("myfile.txt", "r");
if(pFile == NULL)
{
printf("Error opening file");
exit (1);
}
else
{
/* file operations here */
}
return 0;
}
2 Comments
Seth Carnegie
Note that
return doesn't exit the program unless the function happens to be main, whereas exit will terminate the program from any function in which it's called.
asveikau
I have seen that on some systems (mostly Unix-like platforms) returning from
main will also terminate other threads. I'm not sure what C++0x has to say about this, but seeing as until very recently threads were not part of any C or C++ language standard you might see all kinds of behaviors. At any rate the questioner is very clearly asking for exit.In addition to the other responses you can also invoke abort, terminate, quick_exit (exits without calling destructors, deallocating etc; hence the name)
terminate calls abort by default but can call any terminate handler you set.
Example usage of abort and set_terminate (to se the handler used by terminate), quick_exit can be called (see example #2)
// set_terminate example
#include <iostream> // std::cerr
#include <exception> // std::set_terminate
#include <cstdlib> // std::abort
void myterminate () {
std::cerr << "terminate handler called\n";
abort(); // forces abnormal termination
}
int main (void) {
std::set_terminate (myterminate);
throw 0; // unhandled exception: calls terminate handler
return 0;
}
quick_exit/at_quick_exit example:
/* at_quick_exit example */
#include <stdio.h> /* puts */
#include <stdlib.h> /* at_quick_exit, quick_exit, EXIT_SUCCESS */
void fnQExit (void)
{
puts ("Quick exit function.");
}
int main ()
{
at_quick_exit (fnQExit);
puts ("Main function: Beginning");
quick_exit (EXIT_SUCCESS);
puts ("Main function: End"); // never executed
return 0;
}
I'm not entirely certain why one would call quick_exit but it exists and thus I should provide documentation for it (courtesy of http://www.cplusplus.com/reference )
Additionally one can call at_exit as the equivalent of at_quick_exit.
Admittedly I am not all that familiar with set_terminate and terminate as I don't call them myself, but I would guess you could use quick_exit as a terminate handler if you wanted; or a custom one (but please don't quote me on that).
Comments
In C++, you can use exit(0) for example:
switch(option){
case 1:
//statement
break;
case 2:
//statement
exit(0);