用C++实现Linux中shell的ls功能

 实现输出当前目录下的文件名

ls功能：

方法一：

#include <iostream>
#include <algorithm>
#include <stdio.h>
#include <stdlib.h>
#include <dirent.h>
#include <sys/types.h>
#include <string.h>
#include <string>
using namespace std;

bool cmp( string s1,string s2){
  return s1<s2;
}

int main()
{
  DIR *dir;
  char s[100];
  string data[100];
  int tot=0;
  struct dirent *rent;
  dir =opendir(".");
  while(rent=readdir(dir))
  {
      strcpy(s,rent->d_name);
      if(s[0]!='.'){
       data[tot]=s;
      tot++;
      }
  }
  sort(data,data+tot,cmp);
  for(int i=0;i<tot;i++)
   cout<<data[i]<<"  ";
  puts("");
  closedir(dir);
  return 0;
}

方法二：

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <pwd.h>
#include <grp.h>
#include <time.h>
#include <dirent.h>
int do_ls(char *dir,char *filename,int lflag)
{
    int n;
    struct stat buf;
    char out[100];
    struct passwd *pw;
    struct group *gr;
    struct tm *t;
    if(lflag == 0) //如果不带l参数，直接显示文件/目录名
    {
        printf("%s	",filename);
        return 0;
    }
    if(lstat(dir,&buf)<0)
    {
        fprintf(stderr,"stat error:%s
",strerror(errno));
        return -1;
    }
    switch(buf.st_mode & S_IFMT) //获取字符串的属性：普通文件-、目录d、字符设备c、块设备b、管道文件p、连接文件l、套接字文件s
    {
    case S_IFREG:
        printf("-");
        break;
    case S_IFDIR:
        printf("d");
        break;
    case S_IFCHR:
        printf("c");
        break;
    case S_IFBLK:
        printf("b");
        break;
    case S_IFIFO:
        printf("p");
        break;
    case S_IFLNK:
        printf("l");
        break;
    case S_IFSOCK:
        printf("s");
        break;
    }
    for(n=8; n>=0; n--) //打印文件的读写属性：读r、写w、执行x、无权限-
    {
        if(buf.st_mode&(1<<n))
        {
            switch(n%3)
            {
            case 2:
                printf("r");
                break;
            case 1:
                printf("w");
                break;
            case 0:
                printf("x");
                break;
            default:
                break;
            }
        }
        else
        {
            printf("-");
        }
    }
    printf(" %d",buf.st_nlink); //硬链接数，此链接非彼链接，指（包含）目录的个数，文件为1，目录起始为2，再加上目录里包含的目录个数（不递归，只一层）
    pw = getpwuid(buf.st_uid); //所属用户名
    printf(" %s",pw->pw_name);
    gr = getgrgid(buf.st_gid); //所属组名
    printf(" %s",gr->gr_name);
    printf(" %ld",buf.st_size); //字节计总大小
    t = localtime(&buf.st_atime); //最后一次访问时间
    printf(" %d-%d-%d %d:%d"
           ,t->tm_year+1900
           ,t->tm_mon+1
           ,t->tm_mday
           ,t->tm_hour
           ,t->tm_min);
    printf(" %s ",filename);
    if(S_ISLNK(buf.st_mode)) //判断是否为链接，是返回真
    {
        printf(" -> ");
        if(readlink(filename,out,100)==-1)
        {
             //printf("readlink error
");
        }
        printf("%s",out);
    }
    printf("
");
    return 0;
}
int ls_prepare(char *w,int aflag,int lflag) //ls的准备工作
{
    struct stat buf; //man lstat可以看到此结构
    char name[100];
    DIR *dir; //类似打开文件的fd描述符
    struct dirent *pdr; //man readdir可以看到此结构
    if(lstat(w,&buf)<0) //获取文件/目录属性并赋值给buf，该函数和lstat一样，只是当w为链接时，指代他本身，并不存在文件
    {
        fprintf(stderr,"stat error:%s
",strerror(errno));
        return -1;
    }
    if(S_ISDIR(buf.st_mode)) //判断是否为目录，是返回真
    {
        dir = opendir(w); //打开目录
        while ((pdr = readdir(dir))!=NULL) //读/遍历目录
        {
            if(aflag==0) //如果不带a参数，越过以.开头的所有文件/目录
            {
                if(pdr->d_name[0]=='.')
                    continue;
                memset(name,0,100);
                strcpy(name,w); //拷贝
                strcat(name,"/"); //追加
                strcat(name,pdr->d_name);
                do_ls(name,pdr->d_name,lflag);
            }
            else  //有a参数显示所有
            {
                memset(name,0,100);
                strcpy(name,w);
                strcat(name,"/");
                strcat(name,pdr->d_name);
                do_ls(name,pdr->d_name,lflag);
            }
        }
        closedir(dir);
    }
    else  //为文件则直接显示
    {
        do_ls(w,w,lflag);
    }
    return 0;
}
int main(int argc,char **argv)
{
    int aflag =0;
    int lflag =0;
    char c;
    int i;
    while((c = getopt(argc,argv,"al"))!=-1) //解析命令行参数，即-/--后面的字符串和给定的字符串匹配，有未解析字母返回字母或问号（取决于第3个参数），否则返回-1
    {
        switch(c) //此处仅匹配a（所有）和l（列表），即只支持参数a、l
        {
        case 'a':
            aflag =1;
            break;
        case 'l':
            lflag =1;
            break;
        default:
            break;
        }
    }
    if(argc == optind ) 
    {
        ls_prepare("./",aflag,lflag);
    }
    else
    {
        for(i=optind; i<argc; i++) //所有目录都传进去
        ls_prepare(argv[i],aflag,lflag);
    }
    printf("
");
    return 0;
}

ls -l功能：

#include <stdio.h>
#include <sys/types.h>
#include <dirent.h>
#include <sys/stat.h>
#include <pwd.h>
#include <grp.h>

void show_file_info(char* filename, struct stat* info_p) {
 char* uid_to_name(), *ctime(), *gid_to_name(), *filemode();
 void mode_to_letters();
 char modestr[11];

 mode_to_letters(info_p->st_mode, modestr);

 printf("%s", modestr);
 printf(" %4d", (int) info_p->st_nlink);
 printf(" %-8s", uid_to_name(info_p->st_uid));
 printf(" %-8s", gid_to_name(info_p->st_gid));
 printf(" %8ld", (long) info_p->st_size);
 printf(" %.12s", 4 + ctime(&info_p->st_mtime));
 printf(" %s
", filename);

}

void mode_to_letters(int mode, char str[]) {
 strcpy(str, "----------");

 if (S_ISDIR(mode)) {
  str[0] = 'd';
 }

 if (S_ISCHR(mode)) {
  str[0] = 'c';
 }

 if (S_ISBLK(mode)) {
  str[0] = 'b';
 }

 if ((mode & S_IRUSR)) {
  str[1] = 'r';
 }

 if ((mode & S_IWUSR)) {
  str[2] = 'w';
 }

 if ((mode & S_IXUSR)) {
  str[3] = 'x';
 }

 if ((mode & S_IRGRP)) {
  str[4] = 'r';
 }

 if ((mode & S_IWGRP)) {
  str[5] = 'w';
 }

 if ((mode & S_IXGRP)) {
  str[6] = 'x';
 }

 if ((mode & S_IROTH)) {
  str[7] = 'r';
 }

 if ((mode & S_IWOTH)) {
  str[8] = 'w';
 }

 if ((mode & S_IXOTH)) {
  str[9] = 'x';
 }
}

char* uid_to_name(uid_t uid){
 struct passwd* getpwuid(),* pw_ptr;
 static char numstr[10];

 if((pw_ptr = getpwuid(uid)) == NULL){
  sprintf(numstr,"%d",uid);

  return numstr;
 }else{
  return pw_ptr->pw_name;
 }
}

char* gid_to_name(gid_t gid){
 struct group* getgrgid(),* grp_ptr;
 static char numstr[10];

 if(( grp_ptr = getgrgid(gid)) == NULL){
  sprintf(numstr,"%d",gid);
  return numstr;
 }else{
  return grp_ptr->gr_name;
 }
}
void do_ls(char dirname[]) {
 DIR* dir_ptr;
 struct dirent* direntp;

 if ((dir_ptr = opendir(dirname)) == NULL) {
  fprintf(stderr, "ls2: cannot open %s 
", dirname);
 } else {
  while ((direntp = readdir(dir_ptr)) != NULL) {
   dostat(direntp->d_name);
  }

  close(dir_ptr);
 }
}

void dostat(char* filename) {
 struct stat info;

 if (stat(filename, &info) == -1) {
  perror(filename);
 } else {
  show_file_info(filename, &info);
 }
}

int main(int ac,char* av[]){
 if(ac == 1){
  do_ls(".");
 }else{
  while(--ac){
   printf("%s: 
",*++av);
   do_ls(*av);
  }
 }
}