Parsing command will only work for one word commands - c

Question

#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>
#include <readline/readline.h>
#include <readline/history.h>
HIST_ENTRY;
void printPrompt()
{
printf("SB> ");
}
char *readCommandLine()
{
char* myComm = (char*)malloc(1024);
scanf("%s", myComm);
return myComm;
}
char *parseCmd(char *myComm, char **tokens, size_t *index)
{
char *tok;
const char *delim = " ";
*index = 0;
if (tok != NULL)
{
tokens[*index] = tok;
(*index)++;
}
else
{
tokens[*index] = "\0";
printf("%s\n", tok);
return;
}
while(tok != NULL)
{
tok = strtok(NULL, delim);
tokens[*index] = tok;
(*index)++;
}
tokens[*index] = NULL;
return myComm;
}
int isInternalCommand(char *c)
{
int value = 0;
if (strcmp(c, "exit") == 0)
{
value = 1;
printf("%s\n", "yes");
}
return value;
}
void execInternalCommand(char *c)
{
int val = 0;
char a[4];
if (strcmp(c,"exit") == 0)
{
val = val + 1;
}
switch(val)
{
case 1:
_exit(0);
break;
default:
break;
}
}
void executeCommand (char * c, char * const arguments)
{
execvp(c, arguments);
}
int main()
{
char *myComm;
char *parsed;
size_t num_args = 100;
char **tokens = malloc(sizeof(char *) * (num_args+1));
size_t *idx = (size_t *) malloc(sizeof(size_t));
pid_t pid, cpid;
int *status;
while(1)
{
printPrompt();
myComm = readCommandLine();
parsed = parseCmd(myComm, tokens, idx);
char *const *args = tokens;
if (isInternalCommand(parsed))
{
execInternalCommand(parsed);
}
else
{
pid = fork();
if (pid == 0)
{
executeCommand(parsed, args);
printf("%s\n", "executing...");
}
else if (pid > 0)
{
waitpid(cpid, &status, 0);
printf("%s\n", "waiting...");
}
else
{
}
}
free(idx);
}
return 0;
}
So, whenever I try and parse a command, it only works for one word commands.
For example, whenever I try mkdir ./something, it displays mkdir with a "missing operand", which means that it will not make the directory. Additionally, whenever I type man something, like man exec, it will tell something like "which man page do you want to look at?" How do I get around this? Looks like this is a parsing issue.

Answer 1

scanf("%s", myComm);
reads a single whitespace delimited word from stdin. As a result, your commands can only be single words. If you want to read a line, you should use fgets, or, better yet, getline, which will call malloc for you:
char *readCommandLine()
{
char* myComm = 0;
size_t buffer_length = 0;
size_t length = getline(&myComm, &buffer_length, stdin);
if (myComm[length] == '\n')
myComm[length--] = 0; /* strip off trailing newline, if any */
return myComm;
}