Linux C变成小例子——实现ls命令

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div id=”content” contentScore=”2444″>Linux C变成小例子——实现ls命令

/
  ls2.c
 
   Created on: Dec 30, 2013
       Author: Fedora
 /
#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(” %sn”, 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 n”, 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: n”,++av);
   do_ls(av);
  }
 }
}

输出的结果如下图所示：