Created
December 14, 2012 19:48
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| #include <unistd.h> /* Symbolic Constants */ | |
| #include <sys/types.h> /* Primitive System Data Types */ | |
| #include <errno.h> /* Errors */ | |
| #include <stdio.h> /* Input/Output */ | |
| #include <sys/wait.h> /* Wait for Process Termination */ | |
| #include <stdlib.h> /* General Utilities */ | |
| int main() | |
| { | |
| pid_t childpid; /* variable to store the child's pid */ | |
| int retval; /* child process: user-provided return code */ | |
| int status; /* parent process: child's exit status */ | |
| /* only 1 int variable is needed because each process would have its | |
| own instance of the variable | |
| here, 2 int variables are used for clarity */ | |
| /* now create new process */ | |
| childpid = fork(); | |
| if (childpid >= 0) /* fork succeeded */ | |
| { | |
| if (childpid == 0) /* fork() returns 0 to the child process */ | |
| { | |
| printf("CHILD: I am the child process!\n"); | |
| printf("CHILD: Here's my PID: %d\n", getpid()); | |
| printf("CHILD: My parent's PID is: %d\n", getppid()); | |
| printf("CHILD: The value of my copy of childpid is: %d\n", childpid); | |
| printf("CHILD: Sleeping for 1 second...\n"); | |
| sleep(1); /* sleep for 1 second */ | |
| printf("CHILD: Enter an exit value (0 to 255): "); | |
| scanf(" %d", &retval); | |
| printf("CHILD: Goodbye!\n"); | |
| exit(retval); /* child exits with user-provided return code */ | |
| } | |
| else /* fork() returns new pid to the parent process */ | |
| { | |
| printf("PARENT: I am the parent process!\n"); | |
| printf("PARENT: Here's my PID: %d\n", getpid()); | |
| printf("PARENT: The value of my copy of childpid is %d\n", childpid); | |
| printf("PARENT: I will now wait for my child to exit.\n"); | |
| wait(&status); /* wait for child to exit, and store its status */ | |
| printf("PARENT: Child's exit code is: %d\n", WEXITSTATUS(status)); | |
| printf("PARENT: Goodbye!\n"); | |
| exit(0); /* parent exits */ | |
| } | |
| } | |
| else /* fork returns -1 on failure */ | |
| { | |
| perror("fork"); /* display error message */ | |
| exit(0); | |
| } | |
| } |
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