Use C ++ to implement the ls function of shell in Linux.

Use C ++ to implement the ls function of shell in Linux.

Output the file name in the current directory

Ls function:

Method 1:

#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;}

 

Method 2:

# 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) // if the l parameter is not included, the file/directory name {printf ("% s \ t", filename) is displayed directly ); return 0;} if (l Stat (dir, & buf) <0) {fprintf (stderr, "stat error: % s \ n", strerror (errno); return-1;} switch (buf. st_mode & S_IFMT) // obtain the attributes of a string: common file-, Directory d, character Device c, block Device B, MPs, connection file l, socket File 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_ifififo: printf ("p"); break; case S_IFLNK: printf ("l"); break; case S_IFSOCK: printf ("s"); br Eak ;}for (n = 8; n> = 0; n --) // print the read/write attributes of the file: read r, write w, execute x, no permission-{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); // number of hard links. This link is not a link of the other. It refers to the number of (including) directories. The file is 1 and the Directory starts from 2, add the number of directories in the directory (no recursion, only one layer) pw = getpwuid (buf. st_uid); // username printf ("% s", pw-> pw_name); gr = getgrgid (buf. st_gid ); // Group name printf ("% s", gr-> gr_name); printf ("% ld", buf. st_size); // The total size of the byte t = localtime (& buf. st_atime); // The last access time printf ("% 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) // determines whether it is a link. returns true {printf ("->"); if (readlink (filename, out, 100) =-1) {// printf ("readlink error \ n");} printf ("% s", out);} printf ("\ n"); return 0;} Int ls_prepare (char * w, int aflag, int lflag) // The preparation of ls {struct stat buf; // man lstat can see the structure of char name [100]; DIR * dir; // similar to the fd descriptor struct dirent * pdr for opening the file; // man readdir can see this structure if (lstat (w, & buf) <0) // obtain the file/directory attribute and assign it to buf. This function is the same as lstat, but when w is a link, it refers to itself, and there is no file {fprintf (stderr, "stat error: % s \ n", strerror (errno); return-1;} if (S_ISDIR (buf. st_mode) // determines whether it is a directory, returns true {dir = opendir (w); // opens the directory while (pdr = readdi R (dir ))! = NULL) // read/traverse the directory {if (aflag = 0) // if the parameter is not included. all files/directories starting with {if (pdr-> d_name [0] = '. ') continue; memset (name, 0,100); strcpy (name, w); // copy strcat (name, "/"); // append strcat (name, pdr-> d_name); do_ls (name, pdr-> d_name, lflag);} else // All {memset (name, 0,100); strcpy (name, w); strcat (name, "/"); strcat (name, pdr-> d_name); do_ls (name, pdr-> d_name, lflag );}} closedir (dir);} else // indicates the file. {do_ls (w, w, lflag) is displayed directly );} 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) // parse the command line parameter, that is, the string following-/-- matches the given string. If there are unresolved letters, the return letter or question mark (depending on the 3rd parameters) is returned ), otherwise, return-1 {switch (c) // here only match a (all) and l (list), that is, only parameters a and l {case 'a' are supported ': aflag = 1; break; case 'l': lflag = 1; break; default: break;} if (argc = optind) {ls_prepare (". /", aflag, lflag);} else {for (I = optind; I <argc; I ++) // all directories are uploaded to ls_prepare (argv [I], aflag, lflag);} printf ("\ n"); return 0 ;}

 

Ls-l function:

#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\n", 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);  } }}