Running commands with pipes

For dup2 you can have a look here: dup2(2) - Linux man page[^]

For the code, start with an outer loop where you split the input string at the pipe character. Then create a function that takes care of the execution of the each command.

#include "stdafx.h"
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <malloc.h>

size_t TrimWhiteSpace(char *out, size_t len, const char *str);
void ExecuteCommand(const char* command);

int main()
{	
    char input[80] = "ls / tmp | wc - l";
    const char sep[2] = "|";
    char *token = NULL;
    char* command = NULL;
    
    token = strtok(input, sep);
    
    while (token != NULL)
    {
        command = (char*)calloc(strlen(token) + 1, sizeof(char));
        TrimWhiteSpace(command, strlen(token) + 1, token);
        
        printf("%s\n", command);
        
        ExecuteCommand(command);
        
        token = strtok(NULL, sep);
    }
    return 0;
}

size_t TrimWhiteSpace(char *out, size_t len, const char *str)
{
    if (len == 0)
    	return 0;
    
    const char *end;
    size_t out_size;
    
    // Trim leading space
    while (isspace(*str)) 
    	str++;
    
    if (*str == 0)  // All spaces?
    {
    	*out = 0;
    	return 1;
    }
    
    // Trim trailing space
    end = str + strlen(str) - 1;
    while (end > str && isspace(*end)) 
    	end--;
    end++;
    
    // Set output size to minimum of trimmed string length and buffer size minus 1
    out_size = (end - str) < len - 1 ? (end - str) : len - 1;
    
    // Copy trimmed string and add null terminator
    memcpy(out, str, out_size);
    out[out_size] = 0;
    
    return out_size;
}

void ExecuteCommand(const char* command)
{
    // Fork and execute your processes here
}

(The method TrimWhiteSpace, I found at StackOverflow: How do I trim leading/trailing whitespace in a standard way?[^])

This link might be interesting as well: Execute a Program: the execvp() System Call[^]