tari

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>

char *trimSpaces(char *str);

int main(int argc, char *argv[]) {
    if(argc < 1 || argc > 2) {
        char error_message[30] = "An error has occurred\n";
        write(STDERR_FILENO, error_message, strlen(error_message));
        exit(1);
    }
    int PATH_LEN = 512;
    int endAfterThisBatch = 0;
    char* home = getenv("HOME");
    if(argc == 1) {
    for(;;) { /* Goes until "exit" or error. */
        /* Interactive mode */
        char s[513] = {'\0'};
        printf("mysh> ");
        fgets(s, 513, stdin);
        /* remove newline character from input */
        *(strchr(s,'\n')) = '\0';

        /*Handle a batch of concurrent processes (+) per iteration of loop */
        char *concurrent = NULL;
        char *sBAK1 = NULL;
        concurrent = strtok_r(s, ";", &sBAK1);
        while(concurrent != NULL) {
            concurrent = trimSpaces(concurrent);
            /* Sets flag to exit after command group, if "exit" is present */
            if(strcmp(concurrent, "exit") == 0) {
                endAfterThisBatch = 1;
            }
            /* pwd command */
            else if(strcmp(concurrent, "pwd") == 0) {
                char *path = malloc(PATH_LEN);
                path = getcwd(path, PATH_LEN);
                printf(path);
                free(path);
                printf("\n");
            }
            /* blank cd command, back to home dir */
            else if(strcmp(concurrent, "cd") == 0) { /* borked on Vista */
                chdir(home);
            }
            /* cd command with dir to change to */
            else if(strncmp(concurrent, "cd ", 3) == 0) {
                concurrent = concurrent + 2; /* moves past the "cd" */
                concurrent = trimSpaces(concurrent);
                chdir(concurrent);
            }
            else {
                // Handle output redirection
                concurrent = strtok(concurrent, ">");
                concurrent = trimSpaces(concurrent); //Might have spaces between this and >
                char *outf = strtok(NULL, ">");
                int fd = -1;
                if (outf != NULL) {
                    *(outf-1) = '\0';   //Keep redirection from being processed into argv
                    outf = trimSpaces(outf);
                    fd = open(outf, O_WRONLY | O_CREAT | O_TRUNC); //handles errors transparently
                }
                // Parse string into argv for execvp
                int argc = 0;
                char *args = strtok(concurrent, " ");
                char **argv = malloc(sizeof(char*));
                while (args != NULL) {
                    argv = realloc(argv, (argc+1)*sizeof(char*));
                    argv[argc++] = args;
                    args = strtok(NULL, " ");
                }
                argv[argc] = '\0';
                int pid = fork();
                if (pid == 0) {
                    if (fd != -1) {
                        dup2(fd, STDOUT_FILENO);
                    }
                    execvp(argv[0], argv);
                } else {
                    wait(&pid);
                }
                free(argv);
            }
            concurrent = strtok_r(NULL, ";", &sBAK1);
        }

        if(endAfterThisBatch == 1) {
             exit(0);
        }
    } /* End infinite for loop */
    } /* End if statement for interactive mode */


    if(argc == 2) {
        /* Batch mode */
        printf("Batch mode isn't implemented!\n");
    }
    return 0;
}

char *trimSpaces(char *str) {
    char *end;
    // Trim leading space
    while(isspace(*str)) str++;

    // Trim trailing space
    end = str + strlen(str) - 1;
    while(end > str && isspace(*end)) {
        end--;
    }
  // Write new null terminator
  *(end+1) = 0;
  return str;
}