dshlib.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>

#include "dshlib.h"

/*
 *  build_cmd_list
 *    cmd_line:     the command line from the user
 *    clist *:      pointer to clist structure to be populated
 *
 *  This function builds the command_list_t structure passed by the caller
 *  It does this by first splitting the cmd_line into commands by spltting
 *  the string based on any pipe characters '|'.  It then traverses each
 *  command.  For each command (a substring of cmd_line), it then parses
 *  that command by taking the first token as the executable name, and
 *  then the remaining tokens as the arguments.
 *
 *  NOTE your implementation should be able to handle properly removing
 *  leading and trailing spaces!
 *
 *  errors returned:
 *
 *    OK:                      No Error
 *    ERR_TOO_MANY_COMMANDS:   There is a limit of CMD_MAX (see dshlib.h)
 *                             commands.
 *    ERR_CMD_OR_ARGS_TOO_BIG: One of the commands provided by the user
 *                             was larger than allowed, either the
 *                             executable name, or the arg string.
 *
 *  Standard Library Functions You Might Want To Consider Using
 *      memset(), strcmp(), strcpy(), strtok(), strlen(), strchr()
 */
// int build_cmd_list(char *cmd_line, command_list_t *clist)
// {
//     printf(M_NOT_IMPL);
//     return EXIT_NOT_IMPL;
// }

int build_cmd_list(char *cmd_line, command_list_t *clist)
{       
    if ( cmd_line == NULL || strlen(cmd_line) == 0) //is null? or empty?
    {
        return WARN_NO_CMDS; //if no command is given
    }
    char *token; //holds each command that's parsed
    char *rest = cmd_line; //track string
    int num_commands = 0;     //count the # of parsed commands

    while (( token = strtok_r( rest, PIPE_STRING, &rest ) ) != NULL) //tokenize input
    {
        if (num_commands >= CMD_MAX) //make sure commands don't exceed max. allowed
        {
            return ERR_TOO_MANY_COMMANDS;
         }

        //trim all type of spaces
        while ( *token == SPACE_CHAR ) token++; 
        char *end = token + strlen(token) - 1;
        while ( end > token && *end == SPACE_CHAR ) *end-- = '\0';

        //get executable name and arguments
        char *arg_pointer = strchr(token, SPACE_CHAR);
        if (arg_pointer)
        { //separae and move
            *arg_pointer = '\0'; 
            arg_pointer++;        
        }

        //storage command
        strncpy (clist->commands[num_commands].exe, token, EXE_MAX);
        if (arg_pointer)
        {
            strncpy(clist->commands[num_commands].args, arg_pointer, ARG_MAX );
        }

        num_commands ++; //increment
     }

    clist -> num = num_commands;
    return OK; //parsing is correct
}