I have a homework question:
Q7: After executing the following code, a new file named myFile.txt is generated. Is the content in myFile.txt will be consistent? Why? And here is the code:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/wait.h>
int main(int argc, char *argv[]){
printf("hello world (pid:%d)\n", (int)getpid());
int fd = open("myFile.txt", O_CREAT|O_RDWR);
if(fd == -1 ) {
printf("Unable to open the file\n exiting....\n");
return 0;
}
int rc = fork();
if (rc < 0) {
fprintf(stderr, "fork failed\n");
exit(1);
}
else if (rc == 0) {
printf("hello, I am child (pid:%d)\n", (int)getpid());
char myChar='a';
write(fd, &myChar,1);
printf("writing a character to the file from child\n");
}
else {
printf("hello, I am parent of %d (pid:%d)\n",
rc, (int)getpid());
char myChar='b';
write(fd, &myChar,1);
printf("writing a character to the file from parent\n");
}
return 0;
}
The parent will write "a" into myFile.txt while the child writes "b" into that file. I executed this program several times, finding the txt file consistent being "ba", meaning that the parent always comes after the child. However, I noticed that there's no wait() function called by the parent process. Can someone explain why the parent comes after the child?
