quiz1.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <unistd.h>
#include <dirent.h>
#include <string.h>
#include <time.h>
#include <ftw.h>
#include <stdlib.h>

#define BUFSIZE 512

void cat_m(char **s){
    char buffer[BUFSIZE];
    int fd, nread;
    
    fd = open(s[1], O_RDONLY);
    
    nread = read(fd, buffer, BUFSIZE);
    while(nread > 0){
        write(1, buffer, nread);
        nread = read(fd, buffer, BUFSIZE);
    }
    
    close(fd);
}

void cd_m(char **s){
    chdir(s[1]);
}

void cp_m(char **s){
    char buffer[BUFSIZE];
    int fd1, fd2, nread;
    
    fd1 = open(s[1], O_RDONLY);
    
    if (fd1 == -1) {
        return;
    } else {
        fd2 = open(s[2], O_WRONLY | O_CREAT | O_EXCL, 0777);
        
        if(fd2 == -1){
            fd2 = open(s[2], O_WRONLY | O_CREAT | O_TRUNC, 0777);
        }
        
        nread = read(fd1, buffer, BUFSIZE);
        while(nread > 0){
            write(fd2, buffer, nread);
            nread = read(fd1, buffer, BUFSIZE);
        }
    }
    
    close(fd1);
    close(fd2);
}

void mkdir_m(char **s){
    mkdir(s[1], 0777);
}

void ls_m(char **s){
    DIR *dp;
    struct dirent *d;
    dp = opendir(".");
    while((d = readdir(dp)) != NULL){
        if(d->d_name[0] != '.'){
            printf("%s\n", d->d_name);
        }
    }
}

void vi_m(char **s){
    char buffer[BUFSIZE];
    int fd1, nread;
    
    fd1 = open(s[1], O_RDONLY);
    
    if (fd1 == -1) {
        fd1 = open(s[1], O_WRONLY | O_CREAT, 0777);
        while(1) {
            int n = read(0, buffer, BUFSIZE);
            if (strncmp(buffer, "quit", 4) == 0) {
                return;
            }
            write(fd1, buffer, n);
        }
    } else {
        fd1 = open(s[1], O_RDWR);
        
        nread = read(fd1, buffer, BUFSIZE);
        while(nread > 0){
            write(1, buffer, nread);
            nread = read(fd1, buffer, BUFSIZE);
        }
        
        while(1) {
            int n = read(0, buffer, BUFSIZE);
            if (strncmp(buffer, "quit", 4) == 0) {
                return;
            }
            write(fd1, buffer, n);
        }
    }
}

int backup(const char *name, const struct stat *status, int type){
    
    char buffer[BUFSIZE], file1[BUFSIZE], file2[BUFSIZE] = "./TEMP/";
    int fd1, fd2, i, nread;
    
    if(type == FTW_F){
        
        if(strncmp((char*)name, "./TEMP", 6) == 0)
            return 0;
        
        fd1 = open(name, O_RDONLY);
        
        strcpy(file1, name + 2);
        
        for(i=0;i<strlen(file1);i++){
            if(file1[i] == '/')
                file1[i] = '_';
        }
        
        strcat(file2, file1);
        
        fd2 = open(file2, O_WRONLY | O_CREAT, status->st_mode&0777);
        
        nread = read(fd1, buffer, BUFSIZE);
        while(nread > 0){
            write(fd2, buffer, nread);
            nread = read(fd1, buffer, BUFSIZE);
        }
    }
    return 0;
}

void backup_m(char **s){
    mkdir("TEMP", 0777);
    ftw(".", backup, 1);
}

void exec_m(char **s){
    execv(s[0], s);
}

int main(int argc, char **argv) {
    char in[50], *res[20] = {0};
    char *inst[7] = {"cat", "cd", "cp", "mkdir", "ls", "vi", "backup"};
    void (*f[8])(char **) = {cat_m, cd_m, cp_m, mkdir_m, ls_m, vi_m, backup_m, exec_m};
    int i;
    pid_t pid;
    
    while (1) {
        printf("> ");
        gets(in);
        i = 0;
        res[i] = strtok(in, " ");
        if (strcmp(res[0], "exit") == 0)
            exit(0);
        
        while (res[i]) {
            i++;
            res[i] = strtok(NULL, " ");
        }
        
        for (i = 0; i < 7; i++) {
            if (!strcmp(res[0], inst[i]))
                break;
        }
        
        if (i == 1) {
            cd_m(res);
        } else {
            pid = fork();
            if (pid == 0) {
                f[i](res);
                exit(0);
            } else {
                wait(0);
            }
        }
    }
}