FCS351 Prac02 Question 1

#include <stdio.h>
#include <sys/types.h>

int main()
{
    pid_t   pid;
    pid_t   ppid;
    uid_t   uid;

    int i = 0;
    int numChilds = 3;

    pid = getpid();
    ppid = pid;

    while( i < 3 )
    {
        pid = getpid();
        if (pid == ppid)
        {
            printf("parent\n");
            pid = fork();
            i++;
            if ( pid == 0 )
            {
                printf("child\n");
                printf("child ID  : %d\n",getpid());
                printf("parent ID : %d\n",getppid());
                printf("user ID   : %d\n",getuid());
                break;
            }
        }
        else
        {
            printf("error\n");
        }
    }
    return 0;
}

FCS351 Prac02 Question 2

#include<stdio.h>
#include<pthread.h>

// function
void *sleeping()
{
    // execute printf()
    printf("%d says : Hello World!\n",pthread_self());
    // sleep for awhile
    sleep(1);
    // nothing else for thread to execute
    pthread_exit(0);
}

int main()
{
    pthread_t tid[3];

    int i;
    int numThreadsCreated = 0;
    int numThreadsJoined = 0;

    // create 3 threads
    for( i = 0 ; i < 3 ; i++ )
    {
        // create thread and put it in tid array and execute function sleeping
        // with no parameters passed
        if(pthread_create(&tid[i], NULL, sleeping, NULL))
        {
            // if created succesfully, record number of threads running
            numThreadsCreated++;
        }
        // fail to create
        else
        {
            printf("thread cannot be created.\n");
        }
    }
    printf ("%d threads created.\n",numThreadsCreated);

    // Join all created threads
    for ( i = 0 ; i < numThreadsCreated ; i++ )
    {
        // joint all threads in the array of index i
        if(pthread_join(tid[i], NULL))
        {
            // record number of threads joined
            numThreadsJoined++;
        }
        // fail to join
        else
        {
            printf("thread cannot be joined.\n");
        }
    }
    printf ("%d threads joined.\n",numThreadsJoined);
    
    return (0);
}

FCS351 Prac02 Question 3

#include<stdio.h>
#include<fcntl.h>
#include<errno.h>

// take in an arguement from the commandline
int main(int argc, char *argv[])
{
    int fd;
    
    // only accept one arguement from the commandline
    if (argc == 2)
    {
        // try to open the file specified
        fd = open(argv[1], O_RDWR|O_CREAT);
    
        // if fail to open the file, fd is -1
        if(fd == -1)
        {
            // error msgs
            perror("Failed to open file.");
            printf("strerror : %s\n",strerror(errno));
        }
        // file open success
        else
        {
            // print the file descriptor
            printf("File descriptor is : %d\n",fd);
            // write to file
            write(fd, "hahaha" , 6);
        }
        // close the file
        close(fd);
    }
    // not enought or too many arguements
    else
    {
        printf("too many or too few arguements passed.\n");
    }
    
    return(0);
}