ls (my own implementation)

ls (my own implementation)

   9:32 PM       Sayef Azad Sakin

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Little talk about 'ls' (since I have very small knowledge about it):

ls - list directory contents.

The 'ls' program lists information about files (of any type, including directories). Options and file arguments can be intermixed arbitrarily, as usual.

Know details about 'ls' in linux man page: http://unixhelp.ed.ac.uk/CGI/man-cgi?ls

Little talk about coding:

Probably I wouldn't write this code in my entire life unless I got it as my lab assignment :D. It was my 2nd year System Programming lab assignment. However, at first, it seemed very disgusting and painful task to me. But after started coding, it was fun to write the code.

I tried to make my 'ls' as like as linux's 'ls' implementation. Since I was not very familiar with linux, before doing this assignment, firstly I checked out all the options provided by the 'ls' process. Actually, I had to learn about all the functionalities it has :D.

Implementation:

I used c++ as the programming language. I have the name of a directory or file in dirent->d_name & and by using lstat() function, I retrieved all the information about a file or directory.

• I saved each file or directory name and statistics in a vector.
• Applying printing format given by the OPTIONS.
• Print the corresponding information.

A closer look at lstat() in linux man page: http://linux.die.net/man/2/lstat

Here is my coding.........

/*
 * Course: CSE-326 System Programming Lab
 * Assignment No: 02
 * Assignment Name: ls — list directory contents
 * SYNOPSIS: ls [-AacdFfhiklnoqRrSstuw1] [file . . .]
 * Author: Sayef Azad Sakin
 * Roll: 1563
 * Language: c++
 */
 
#ifndef BLOCKSIZE
#define BLOCKSIZE 512
#endif
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <string>
#include <vector>
#include <dirent.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <pwd.h>
#include <grp.h>
#include <time.h>
#include <climits>
#include <algorithm>
using namespace std;

#define eps 1e-11
#define mx 1000

struct files{
 string name, full_path;
 struct stat st;
 files(string ps, string s, struct stat &ss){
  full_path = ps;
  name = s;
  st = ss;
 }
};

vector < files > name, dir_name[10], dir_path, rfile, rdir;
vector < files >:: iterator it;
bool flag[30];
int tot_dir;
char chk[] = {'A','a','c','d','F','f','h','i','k','l','n','o','q','R','r','S','s','t','u','w','1'};

bool comp(const files &a, const files &b){
 if(flag[15]){//-S
  if(a.st.st_size == b.st.st_size){
   if(flag[17]){//-t
    if(a.st.st_mtime == b.st.st_mtime)return (a.name<b.name);
    return (a.st.st_mtime < b.st.st_mtime);
   }
   return (a.name<b.name);
  }
  return (a.st.st_size > b.st.st_size);
 }
 if(flag[17]){//-t
  if(a.st.st_mtime == b.st.st_mtime)return (a.name<b.name);
  return (a.st.st_mtime < b.st.st_mtime);
 }
 if(flag[2]){//-c
  if(a.st.st_ctime == b.st.st_ctime)return (a.name<b.name);
  return (a.st.st_ctime < b.st.st_ctime);
 }
 if(flag[18]){//-u
  if(a.st.st_atime == b.st.st_atime)return (a.name<b.name);
  return (a.st.st_atime < b.st.st_atime);
 }
 return (a.name<b.name);
}

int getfile(files fdes);
int chkflag(char *str);
void print(const files fdes);

int main(int argc, char **argv){
 int argpos, i, sz;
 bool ok;
 char path[mx], cwd[mx];
 dirent *dirp;
 DIR *dp;
 struct stat f_stat;
 //initialize();
 //parsing starts here
 ok = 0;
 for(argpos = 1; argpos < argc; argpos++){
  if(argv[argpos][0]=='-'){
   if(chkflag(argv[argpos])==-1){puts("argument error");return 2;}
  }
  else{
   if (lstat(argv[argpos], &f_stat) == -1){puts("statistics error");return -1;}
   if(S_ISREG(f_stat.st_mode) || !strcmp(argv[argpos],".") || !strcmp(argv[argpos],".."))rfile.push_back(files(argv[argpos],argv[argpos],f_stat));
   else if(S_ISDIR(f_stat.st_mode))rdir.push_back(files(argv[argpos],argv[argpos],f_stat));
   ok = 1;
  }
 }
 if(!ok){
  if( !getcwd(cwd,mx) ) return 1;
  
  if( !(dp = opendir(cwd)) ){puts("error on opening current directory");return 3;}
  while( (dirp = readdir(dp)) ){
   strcpy(path,".");
   strcat(path,"/");
   strcat(path,dirp->d_name);
   if (lstat(path, &f_stat) == -1){puts("statistics error");return -1;}
   if(S_ISREG(f_stat.st_mode) || !strcmp(dirp->d_name,".") || !strcmp(dirp->d_name,".."))rfile.push_back(files(path,dirp->d_name,f_stat));
   else if(S_ISDIR(f_stat.st_mode))rdir.push_back(files(path,dirp->d_name,f_stat));
  }
  if( closedir(dp) < 0 ){puts("can't close directory");return -1;}
 }
 //parsing ends here

 //sorting starts here
 sort(rfile.begin(),rfile.end(),comp);
 sort(rdir.begin(),rdir.end(),comp);
 if(flag[14]){//-r
  reverse(rfile.begin(),rfile.end());
  reverse(rdir.begin(),rdir.end());
 }
 //sorting ends here
 
 sz = rfile.size();
 for(i=0;i<sz;i++)
  print(rfile[i]);
 if(!ok || flag[3]){//-d
  sz = rdir.size();
  for(i=0;i<sz;i++)
   print(rdir[i]);
  return 0;
 }
 puts("");
 sz = rdir.size();
 
 if(ok || flag[13]){//-R
  for(i=0;i<sz;i++){
   cout << rdir[i].name << ":(under this direcotry) " << endl;
   if(getfile(rdir[i])==-1)return 5;
  }
 }
 return 0;
}

int getfile(files fdes){
 dirent *dirp;
 DIR *dp;
 vector < files > tfile, tdir;
 struct stat file_stat;
 char path[mx], tpath[mx];
 int sz, i;
 strcpy(path,fdes.full_path.c_str());
 if( !(dp = opendir(path)) ){puts("error on opening directory");return -1;}
 while( (dirp = readdir(dp)) ){
  strcpy(tpath,path);
  sz = strlen(tpath);
  if(tpath[sz-1]!='/'){
   tpath[sz] = '/'; tpath[sz+1] = 0;
  }
  strcat(tpath,dirp->d_name);
  //printf("%s\n",tpath);
  if (lstat(tpath, &file_stat) == -1){puts("statistics error");return -1;}
  if(S_ISREG(file_stat.st_mode) || !strcmp(dirp->d_name,".") || !strcmp(dirp->d_name,".."))tfile.push_back(files(tpath,dirp->d_name,file_stat));
  else if(S_ISDIR(file_stat.st_mode))tdir.push_back(files(tpath,dirp->d_name,file_stat));
 }
 if( closedir(dp) < 0 ){puts("can't close directory");return -1;}
 
 //sorting starts here
 sort(tfile.begin(),tfile.end(),comp);
 sort(tdir.begin(),tdir.end(),comp);
 if(flag[14]){//-r
  reverse(tfile.begin(),tfile.end());
  reverse(tdir.begin(),tdir.end());
 }
 //sorting ends here
 
 sz = tfile.size();
 for(i=0;i<sz;i++)
  print(tfile[i]);
 sz = tdir.size();
 for(i=0;i<sz;i++)
  print(tdir[i]);
 puts("");
 if(flag[3])return 0;//-d
 if(flag[13]){
  sz = tdir.size();
  for(i=0;i<sz;i++){
   cout << tdir[i].name << ":(under this direcotry) " << endl;
   if(getfile(tdir[i])==-1)return -1;
  }
 }
 return 0;
}

int chkflag(char *str){
 bool ok;
 int i,j;
 for(i = 1;str[i]; i++){
  if(str[i]=='R' && flag[3])continue;
  ok = 0;
  for(j=0;j<21;j++){
   if(chk[j]=='h' && str[i]=='k')flag[j] = 0;
   else if(chk[j]=='k' && str[i]=='h')flag[j] = 0;
   else if(chk[j]=='1' && str[i]=='l')flag[j] = 0;
   else if(chk[j]=='l' && str[i]=='1')flag[j] = 0;
   else if(chk[j]=='c' && str[i]=='u')flag[j] = 0;
   else if(chk[j]=='u' && str[i]=='c')flag[j] = 0;
   else if(chk[j]=='q' && str[i]=='w')flag[j] = 0;
   else if(chk[j]=='w' && str[i]=='q')flag[j] = 0;
   else if(chk[j]=='R' && str[i]=='d')flag[j] = 0;
   
   if(chk[j]==str[i]){ok=1;break;}
  }
  if(ok)flag[j] = 1;
  else return -1;
 }
 return 0;
}

void print(const files fdes){
 double sz;
 struct tm *ts;
 char ptime[20];
 struct passwd *ps;
 struct group *gr;
 sz = fdes.st.st_size;
 if(!flag[1] && (fdes.name == "." || fdes.name == ".."))return;
 if(flag[7])printf("%u ",fdes.st.st_ino);//-i
 if(flag[16]){//-s
  sz = fdes.st.st_blocks*512;
  if(!flag[6] && !flag[8]){
   sz /=1024;
   printf("%5.0lf ",ceil(sz));
  }
 }
 if(flag[6] && flag[16]){//-h
  if(sz>1073741824 || fabs(sz-1073741824)<eps){
   sz /= 1073741824;
   printf("%.1lfG ",sz+eps);
  }
  else if(sz>1048576 || fabs(sz-1048576)<eps){
   sz /= 1048576;
   printf("%.1lfM ",sz+eps);
  }
  else if(sz>1024 || fabs(sz-1024)<eps){
   sz /= 1024;
   printf("%.1lfK ",sz+eps);
  }
  else printf("%.0lf ",sz);
 }
 if(flag[8] && flag[16]){//-k
  sz /= 1024;
  printf("%5.0lf ",ceil(sz));
 }
 if(flag[9] || flag[10] || flag[13]){//-l & -n
  //file mode
  //entry type
  if(S_ISBLK(fdes.st.st_mode))printf("b");
  else if(S_ISCHR(fdes.st.st_mode))printf("c");
  else if(S_ISDIR(fdes.st.st_mode))printf("d");
  else if(S_ISLNK(fdes.st.st_mode))printf("l");
  else if(S_ISSOCK(fdes.st.st_mode))printf("s");
  else if(S_ISFIFO(fdes.st.st_mode))printf("p");
  else if(S_ISREG(fdes.st.st_mode))printf("-");
  //owner permission
  printf((fdes.st.st_mode & S_IRUSR)?"r":"-");
  printf((fdes.st.st_mode & S_IWUSR)?"w":"-");
  if((S_ISREG(fdes.st.st_mode) || S_ISDIR(fdes.st.st_mode)) && fdes.st.st_mode & 0111)
   printf((fdes.st.st_mode & S_ISUID)?"s":"x");
  else
   printf((fdes.st.st_mode & S_ISUID)?"S":"-");
  //group permission
  printf((fdes.st.st_mode & S_IRGRP)?"r":"-");
  printf((fdes.st.st_mode & S_IWGRP)?"w":"-");
  if((S_ISREG(fdes.st.st_mode) || S_ISDIR(fdes.st.st_mode)) && fdes.st.st_mode & 0111)
   printf((fdes.st.st_mode & S_ISGID)?"s":"x");
  else
   printf((fdes.st.st_mode & S_ISGID)?"S":"-");
  //other permission
  printf((fdes.st.st_mode & S_IROTH)?"r":"-");
  printf((fdes.st.st_mode & S_IWOTH)?"w":"-");
  if((S_ISREG(fdes.st.st_mode) || S_ISDIR(fdes.st.st_mode)) && fdes.st.st_mode & 0111)
   printf((fdes.st.st_mode & S_ISVTX)?"t":"-");
  else
   printf((fdes.st.st_mode & S_ISVTX)?"T":"-");
  
  //number of links
  printf(" %u",fdes.st.st_nlink);
  
  //user name & group name
  if(flag[10])printf(" %5u%5u",fdes.st.st_uid,fdes.st.st_gid);
  else{
   ps = getpwuid(fdes.st.st_uid);
   printf(" %s ",ps->pw_name);
   if(!flag[13]){
    gr = getgrgid(fdes.st.st_gid);
    printf(" %s",gr->gr_name);
   }
  }
  
  //no of bytes
  sz = fdes.st.st_size;
  if(flag[6]){//-h
   if(sz>1073741824 || fabs(sz-1073741824)<eps){
    sz /= 1073741824;
    printf("%10.1lfG ",sz+eps);
   }
   else if(sz>1048576 || fabs(sz-1048576)<eps){
    sz /= 1048576;
    printf("%10.1lfM ",sz+eps);
   }
   else if(sz>1024 || fabs(sz-1024)<eps){
    sz /= 1024;
    printf("%10.1lfK ",sz+eps);
   }
   else printf("%10.0lf ",sz);
  }
  else if(flag[8]){//-k
   sz /= 1024;
   printf("%10.0lf ",ceil(sz));
  }
  else printf("%10.0lf ",sz);
  
  //year-month-day hh:mm
  ts = localtime(&fdes.st.st_mtime);
  strftime(ptime, sizeof(ptime), "%Y-%m-%d %H:%M", ts);
  printf("%s ", ptime);
 }
 
 cout << fdes.name;
 if(flag[4]){//-F
  if(S_ISDIR(fdes.st.st_mode))printf("/");
  else if(S_ISREG(fdes.st.st_mode) && fdes.st.st_mode & 0111)printf("*");
  else if(S_ISLNK(fdes.st.st_mode))printf("@");
  //else if(S_IFWHT(fdes.st.st_mode))printf("@");
  else if(S_ISSOCK(fdes.st.st_mode))printf("=");
  else if(S_ISFIFO(fdes.st.st_mode))printf("|");
 }
 puts("");
}

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MAKEFILE (at a glance)

MAKEFILE (at a glance)

   8:15 PM       Sayef Azad Sakin

---

Sample code

 
project1: data.o main.o io.o
        cc data.o main.o io.o -o project1
data.o: data.c data.h
        cc -c data.c
main.o: data.h io.h main.c
        cc -c main.c
io.o: io.h io.c
        cc -c io.c #this is a comment

Syntex
target : source file(s)
command (must be preceded by a tab)

#command to use user defined makefile name
make -f mymakefile

Macros in make
The make program allows to use macros, which are similar to variables, to store names of files. The format is as follows:
OBJECTS = data.o io.o main.o
Whenever you want to have make expand these macros out when it runs, type the following corresponding string $(OBJECTS).

Here is sample Makefile again, using a macro.

OBJECTS = data.o main.o io.o
project1: $(OBJECTS)
        cc $(OBJECTS) -o project1
data.o: data.c data.h
        cc -c data.c
main.o: data.h io.h main.c
        cc -c main.c
io.o: io.h io.c
        cc -c io.c

You can also specify a macro's value when running make, as follows:
make 'OBJECTS=data.o newio.o main.o' project1
This overrides the value of OBJECTS in the Makefile

Special Macros
CC:
Contains the current C compiler. Defaults to cc.
CFLAGS:
Special options which are added to the built-in C rule.
$@:
Full name of the current target.
$?:
A list of files for current dependency which are out-of-date.
$<:
The source file of the current (single) dependency.

External Links:
http://www.eng.hawaii.edu/Tutor/Make/1.html
http://www.opussoftware.com/tutorial/TutMakefile.htm

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