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)
{
    char *pointer = cmd_line;
    char* pipe = strchr(pointer, PIPE_CHAR);

    clist->num = 0;

    command_t new_command;

    void make_command(command_t new_command, char *pointer, command_list_t *clist, size_t sub_length){
        while (*pointer == ' '){
            pointer++;
        }
        char *space = strchr(pointer, SPACE_CHAR);

        if (space==NULL){
            memset(new_command.exe, 0, sizeof(new_command.exe));
            size_t exe_length = strlen(pointer);
            strncpy(new_command.exe, pointer, exe_length);

            memset(new_command.args, 0, sizeof(new_command.args));
            new_command.args[0] = '\0';

            clist->commands[clist->num] = new_command;
            clist->num = clist->num+1;
        } else{
            while (*space==' '){
                space++;
            }
            size_t exe_length = space - pointer;
            memset(new_command.exe, 0, sizeof(new_command.exe));
            strncpy(new_command.exe, pointer, exe_length);
            new_command.exe[exe_length] = '\0';
            
            size_t arg_length = pointer + sub_length - space;
            memset(new_command.args, 0, sizeof(new_command.args));
            strncpy(new_command.args, space, arg_length);
            new_command.args[arg_length] = '\0';
            clist->commands[clist->num] = new_command;
            clist-> num = clist->num + 1;
        }
    }

    while(pointer != NULL){

        pipe = strchr(pointer, PIPE_CHAR);

        if (pipe==NULL){
            size_t command_length = strlen(pointer);
            make_command(new_command, pointer, clist, command_length);
            pointer = pipe;
        } else{
            size_t sub_length = pipe - pointer;

            char sub_string[sub_length + 1];
            strncpy(sub_string, pointer, sub_length);
            sub_string[sub_length] = '\0';

            make_command(new_command, sub_string, clist, sub_length);
            pointer = pipe + 1;
            
        }

    }

    return OK;
}