Processes - Evan Carlstrom #374
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… to help with answering questions
…referencing example code)
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You have some good looking stuff here. I would only recommend the following if statement,
if (rc < 0) {
fprintf(stderr, "fork failed\n");
exit(1);
}
/*stderr is the standard error stream the default destination for error messages and other diagnostic warnings. Like stdout
it is usually also directed by default to the text console(generally, on the screen).
*/
exit so its prototype looks like this
void exit(int status);
Returns nothing but indicates whehter the program terminated normally.
exit_success successful termination
0 successful termination
exit_failure unsuccessful termination
exit will terminate the program and everything that comes after it will not show up.
This is for ex1.c however, you will want a check for if you were to ever receive a error or interruption after calling fork()
…x changes to learn more about process ordering and the different versions of exec() from ex4.
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Thanks, will try and add some error handling into the forked processes from now on. I looked up a bit about "rc"; its function is to represent whatever is returned, correct? So this would basically mean that (rc < 0) indicates an unsuccessful return that will lead to an unsuccessful termination. |
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Sorry |
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Okay, got it then. This would just be another 'if' case to add to the existing checks. |
…tially, child process now always prints first and waitpid() is in the proper location
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For ex4 we want to set up the main to accept argc and argv[] this would be entered in on the command line and read into the program and then worked with accordingly. Your code may infact generate the correct output but you may see functions where main will be prepared to accept arguments so I wanted to show you this.
int main(int argc, char* argv[])
{
printf("Parent process here\n");
int rc = fork();
if (rc < 0) {
fprintf(stderr, "fork failed\n");
exit(1);
} else if (rc == 0) {
printf("Child process here\n");
// execl("/bin/ls", "ls", "-l" (char *) NULL);
// char *args[] = {"ls", "-l", NULL};
// execv("/bin/ls", args);
//execlp("ls", "ls", "-l", (char *) NULL);
char *args[] = {"ls", "-l", NULL};
execvp("ls", args);
} else {
int wc = waitpid(rc, NULL, 0);
}
return 0;
}
This way we would then pass "/bin/ls"
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Thanks, I'll take a look at that code when I'm done with the repo today and see how well I understand it. |
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The biggest difference is we could replace |
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