UNIX Shell

//Kevin Brough
//UNIX Shell
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <dirent.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
void parse(char *line, char *argv[]){ //we'll go through and parse our command line
  argv[0] = strtok(line, " ()|&;\t\n");
  int i;
  for(i = 1; i < 19; i = i++) {
    argv[i] = strtok(NULL, " ()|&;\t\n");
    if (argv[i] == NULL){
        break;
    }
  }
  argv[19] = NULL;//making sure to set the end to null
}
int main(void){
    char buffer[100];
    int argc;
    char *argv[20];
    int status, pid;
    int redirectOut, redirectIn, appendOut;
    while(1){
        redirectOut = redirectIn = appendOut = 0;//resetting the booleans for cleanliness
        printf("> ");
        fgets(buffer, 100, stdin);
        parse(buffer, argv);
        if ((strcmp("exit", argv[0])) == 0){//first two built in functions
            exit(0);
        }
        else if(!strcmp("cd", argv[0])){
            if(chdir(argv[1]) != 0) {
                printf("Cannot change dir\n");
            }
        }
        else{
            for (argc=1; argv[argc] != 0; argc++){//checking the commandline arguments to see if there's redirection etc.
                if (!strcmp(argv[argc], ">>")){//the checking
                    appendOut = 1;//making sure we set the boolean value
                    argv[argc] = 0;//saving the args then breaking out
                    break;
                }
                else if(!strcmp(argv[argc], ">")){
                    redirectOut  = 1;
                    argv[argc] = 0;
                    break;
                }
                else if(!strcmp(argv[argc], "<")){
                    redirectIn  = 1;
                    argv[argc] = 0;
                    break;
                }
            }
            pid = fork();
            if (pid == 0){//child process
                if (appendOut){//first we check which redirect/append it is
                    if (!freopen(argv[argc+1], "ab", stdout)){//do the coresponding freopen and check if it's null
                        fprintf(stderr, "Error: Failed to append output to: ");//and do the error handling
                        perror(argv[argc+1]);
                        exit(-1);
                    }
                }//repeat for the next two
                else if (redirectOut){
                    if (!freopen(argv[argc+1], "wb", stdout)){
                        fprintf(stderr, "Error. Failed to redirect output to: ");
                        perror(argv[argc+1]);
                        exit(-1);
                    }
                }
                else if (redirectIn){
                    if (!freopen(argv[argc+1], "rb", stdin)){
                        fprintf(stderr, "Error. Failed to redirect input from: ");
                        perror(argv[argc+1]);
                        exit(-1);
                    }
                }
                execvp(argv[0], argv);//where all the work is done
                perror(argv[0]);
                exit(1);
            }
            else if (pid > 0){//parent process
                wait(&status);
            }
            else{//should the unimaginable happen
                perror("fork");
            }
        }
    }
    return 0;
}