C execlp() not correctly parsing parameters string

I'm building a shell for an Operating Systems class that must use exec() or one of its variants to execute external commands. Currently, I'm using execlp(command,command_parameters, (char *) NULL). This runs the command just fine (e.g. ls returns a standard directory listing), but doesn't seem to parse any of the parameters (e.g. running mkdir hello throws an error "hello: missing operand... Try 'hello --help' for more information). What am I missing?

            else // Try to handle an external command
        {
            char *command_parameters = malloc(sizeof(raw_command)-sizeof(comman开发者_Go百科d));
            strcpy(command_parameters, raw_command+strlen(command)+1);
            pmesg(1, "Command is %s.\n", command);
            pmesg(1, "The command parameters are %s.\n", command_parameters);
            pid_t pid = fork();
            pmesg(1, "Process forked. ID = %i. \n", pid);
            int status;
            if (fork < 0)
            {
                printf("Could not fork a process to complete the external command.\n");
                exit(EXIT_FAILURE);
            }
            if (pid == 0) // This is the child process
            {
                pmesg(1, "This is the child process, running execlp.\n");
                if (execlp(command, command_parameters, (char *) NULL) < 0)
                {
                    printf("Could not execute the external command.\n");
                    exit(EXIT_FAILURE);
                }
                else    { pmesg(1, "Executed the child process.\n"); }
            }
            else {while(wait(&status) != pid); } // Wait for the child to finish executing
            pmesg(1, "The child has finished executing.\n");
        }

(pmesg is a debug tag that prints the statement given a certain debug level).

Thanks!

A couple of issues here:

1. execlp( const char *file, const char *arg, ...) expects the arguments to be split up and passed separately, not as one big string.
2. The first arg (after const char *file) is by convention, the name of the executable you're running, which gets put into argv[0] in the called program. The first parameter, thus, will need to go after that.

e.g.:

execlp( command, command, arg1, arg2, ..., (char *)NULL );

With what you have, doing it like:

execlp( command, command, command_parameters, (char *)NULL );

will probably, as-is, take care of your issue with "mkdir", "hello", but you're still not splitting the command_parameters string up, so it won't work without modification for commands with more than one argument.

EDIT: P.S. Your line

if (fork < 0)

should be

if (pid < 0)