Ndtyjky

I have a project that I am currently stuck on. Here is what I got so far.

#include <stdlib.h>

#include <string.h>

#include <stdio.h>

#include <sys/wait.h>



#define newsh_buffSize 1024

#define newsh_tok_buff 64

#define newsh_tok_delim " trna"



// Reading from standard input and return //

void *newsh_read_line(void){

char *line = NULL;

ssize_t bufsize = 0;

getline(&line, &bufsize, stdin);

return line;

}

char** newsh_split_line(char *line){

int bufsize = newsh_tok_buff;

int place = 0;

char **tokens = malloc(bufsize * sizeof(char*));

char *token;



if(!tokens) {

    fprintf(stderr, "Allocation Errorn");

    exit(EXIT_FAILURE);

}



token = strtok(line, newsh_tok_delim);

while(token != NULL) {

    tokens[place] = token;

    place++;



    if(place <= bufsize){

        bufsize += newsh_tok_buff;

        tokens = realloc(tokens, bufsize * sizeof(char*));

        if(!tokens) {

            fprintf(stderr, "Allocation Errorn");

            exit(EXIT_FAILURE);

        }

    }

    token = strtok(NULL, newsh_tok_delim);

}

tokens[place] = NULL;

return tokens;

}

void newsh_loop(void){

char *line;

char **args;

int status;



do{

printf(">>");

line = newsh_read_line();

args = newsh_split_line(line);

status = newsh_execute(args);



free(line);

free(args);

}while(status);

}



int newsh_launch(char **args) {

pid_t pid, wpid;

int status;



pid = fork();

if (pid == 0) {

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

       perror("newsh");

    }

    exit(EXIT_FAILURE);

 }

 else if (pid < 0) {

     perror("newsh");

 }

 else {

     do{

         wpid = waitpid(pid, &status, WUNTRACED);

     }while(!WIFEXITED(status) && !WIFSIGNALED(status));

 }

 return 1;

 }



// Declaring Built in Commands //

int newsh_cd(char **args);

int newsh_bp(char **args);

int newsh_var(char **args);

int newsh_quit(char **args);



char *builtin_str = {

"cd",

"quit"

 };



int(*builtin_func)(char **) = {

&newsh_cd,

&newsh_quit,

&newsh_var,

&newsh_bp

};



int newsh_num_builtin(){

return sizeof(builtin_str)/sizeof(char*);

}



// Command Implementation //

int newsh_cd(char **args) {



}



int newsh_quit(char **args){

return 0;

}



int newsh_execute(char **args) {

int j;



if(args[0] == NULL) {

    return 1;

}

for(j = 0; j < newsh_num_builtin(); j++) {

    if(strcmp(args[0], builtin_str[j]) == 0) {

        return(*builtin_func[j])(args);

    }

}

return newsh_launch(args);

}



// MAin function Implementation //

int main(int args, char **argv) {

newsh_loop();

EXIT_SUCCESS;

}

I have to write a shell in C/C++ without using Unix system() library routine to execute the command line. The shell is called newsh and must be able to handle the following built-in commands:
1) set variable value : variable being any reasonable variable name and value being a number / a token. Keep in mind variables are case sensitive.
2) cd directoryName: change the directory to the "directoryName" which can be either absolute (starting with /) or relative (no /). cd must also have a single parameter.
3)bp, list all processes running in the background, in any format but shouldn't rely on external programs like ps to create its output
4) quit, exits with exit status 0, should also accept on the input stream and treat it as if the user has typed quit.

In my code there's some program control commands, but for right now I would like to be able to just get these 4 builtin commands going. Basically I need to readline from standard input, break the lines into tokens, and check for correctness. In the end I would like to be to test my program by using a testfile by envoking newsh < testfile . Any help or input on these 4 is greatly appreciated, thanks!