Develop a shell in C language. Create a main() function that prints a prompt, ac

Question

Develop a shell in C language.

Create a main() function that prints a prompt, accepts input, and tokenizes the input and passes the argument vector to an excuteCmd() function by using the execution int executeCMD(char**args); it will return -1 if n error is found, but a zero if not. You can exit the shell by entering an x at the prompt.

Create an executeCmd() function that can execute any program in the foreground or background as well as redirect the output of any program to a file. It will be able to execute arguments such as list files in the current directory, display directory, display number of lines or make a new directory (ls, ls -a, mkdir, wc). The program should run in the background and does not need to wait for completion before the prompt is displayed again. Output can be redirected to a file.

Explanation / Answer

//below program is used to initialize prompt, tokenize arguments , run and print array arguments

char **argv;
char argu[64];   //Global Variables  

int main(int argc, char** argv)
{
    mainloop();                      //to call loop main for functions
    return (EXIT_SUCCESS);
}

void promptsh()
{                       //prompt execution
    printf ("hai");
}

void mainloop()
{                    //Loop to call the functions
    while(1){
        promptsh();
        argv = (char**)malloc(sizeof(char*)*50); //allocation of memory for argv
        excuteCmd(argu, argv);

        if((strcmp(argv[0],"exit" )) == 0)
{
//check for exit
            return 0;
        }
        run();
        print();
      
    }
}

void excuteCmd(char* argu, char** argv)
{
    int i=0,j=0;
    char c;
    char* token;
    while((c = getchar()) != ' ' )

{ //gets character and checks for end of line
        argu[i] = c;
        i++;
    }
    argu[i] = '';
    token = strtok(argu, " ,.");     //tokenize the command
    while (token != NULL)
{
        argv[j] = token;         //passing command for argus array
        token = strtok(NULL, " ,.");
        j++;
    }
    argv[j] = NULL;
}

void run()
{                      //Function to call fork and execute with errors
    pid_t childpid = fork();
    int retstat;
    if(childpid == -1){                           //if fail to fork
        printf("failed to fork");
        exit(1);
    }
    else if(childpid == 0){                      //Child process
        if (execvp(*argv, argv) < 0){
            printf("execution error ");
            exit(1);
        }
        else{                                   //sucessfully executed
            printf("executed");
        }
    }
    int c=(int)waitpid(childpid, &retstat, 0);
    if (retstat == 0)                 // to check if child process terminated without error.
        {
            printf("The normal termination of child process . ");
        }

    if (returnStatus == 1)             //to terminate with error
        {
            printf("The error in child process !. ");  
        }
  
}

void print()                   //to print the arguments
{
    int i = 0;
    while(argv[i] != NULL)
   {
        printf("Argv%d: %s ",i, argv[i] );
        i++;
    }
}

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