Write a C program that behaves like a shell which displays the command prompt ‘myshell$’. It accepts the command, tokenize the command line and execute it by creating the child process. Also implement the additional command ‘count’ as myshell$ count c filename: It will display the number of characters in given file myshell$ count w filename: It will display the number of words in given file myshell$ count l filename: It will display the number of lines in given file

 

#include<sys/types.h>

#include<sys/stat.h>

#include<fcntl.h>

#include<stdio.h>

#include<stdlib.h>

#include<string.h>

void make_toks(char *s,char *tok[])

{

    int i=0;

    char *p;

    p=strtok(s, " ");

    while (p!=NULL)

    {

        tok[i++]=p;

        p=strtok(NULL," ");

    }

    tok[i]=NULL;

}

void count(char *fn,char op)

{

    int fh,cc=0,wc=0,lc=0;

    char c;

    fh=open(fn,O_RDONLY);

    if (fh==1)

    {

        printf("File %s not found \n ",fn);

        return;

    }

   

    while (read (fh,&c,1>0))

    {

        if (c==' ')

            wc++;

        else if (c=='\n')

        {

            wc++;

            lc++;

        }

        cc++;

    }

    close(fh);

    switch(op)

    {

        case 'c' : printf("Number of characters : %d \n ",cc-1);

               break;

               

        case 'w' : printf("Number of words : %d \n ",wc);

               break;

               

        case 'l' : printf("Number of Lines : %d \n ",lc+1);

               break;

    }

}

int main()

{

    char buff[80],*args[10];

    int pid;

   

    while(1)

    {

        printf("myshell$");

        fflush(stdin);

        fgets(buff,80,stdin);

        buff[strlen(buff)-1]='\0';

        make_toks(buff,args);

        if (strcmp(args[0],"count")==0)

            count(args[2],args[1][0]);

        else

        {

            pid=fork();

            if (pid > 0)

                wait();

            else

            {

                if (execvp(args[0],args)==-1)

                    printf("Bad Command\n");

            }

        }

    }

    return 0;

}