#include <dirent.h>
#include <string.h>
#include <unistd.h>
#include <malloc.h>
/*
    cut a string by sep character, 
    return a pointer of array string
*/
char **str2arword(const char *str,char sep){
  if(str==NULL) return NULL;
  char *path=str;
  size_t len=strlen(path);
  size_t frag=0,r=0,count=0,msize;
  char **vpath;
  /*first count how many*/
  while(*path)	if(*path++==sep) frag++;
  vpath=(char **)malloc( (frag+2)*sizeof(char*)+len+1 );
  path=str;
  vpath[r]=vpath+frag+2;
  while(*path){
	*(vpath[r]+count++)=*path++;
	if(*path==sep) {
	  *(vpath[r]+count)=NULL;
	  vpath[r+1]=vpath[r]+count+1;
	  count=0,path++,r++;
	}
  }
  vpath[r+1]=NULL;
  return vpath;
}

/*23:00
    get a list of file exec in PATH environment variable
*/
char **get_list_exec(const char *epath){
  #define MAX_NUMBER_POINTER    512
  char *path = epath;
  char **vcpt = 0;
  size_t r=0,len=0,item=0,count=1;
  char **vret=(char **)malloc(sizeof(char *)*MAX_NUMBER_POINTER);
  struct dirent *dent;
  DIR *dirp;
  if(vret==NULL) return -1;
  if(epath==NULL) path = getenv("PATH");
  vcpt = str2arword(path,':');
  /*in this loop I got the total len of all string and number of item*/
  while(vcpt[r]){
    dirp= opendir(vcpt[r]);
    if(dirp==NULL) goto end_loop;
    while( dent=readdir(dirp) ) {
      if( (strcmp(dent->d_name,".")) &&  strcmp(dent->d_name,"..") )
        if((dent->d_type==DT_REG)||(dent->d_type==DT_LNK)){
          char buf[512]; /*form a canonical name*/
          strcpy(buf,vcpt[r]);strcat(buf,dent->d_name);
          if(! access(buf,X_OK))
          {
              size_t len1 = strlen(dent->d_name);
              char *get = malloc(len1+1);
              if(get==NULL) return -1;
              strcpy(get,dent->d_name);
              vret[item]=get;
              len +=len1;
              item++;
          }
        }
      if(item>=MAX_NUMBER_POINTER){
        count++;
        void *tmp=malloc(sizeof(char *)*MAX_NUMBER_POINTER*count);
        if(tmp==NULL) return -1;
        memcpy(tmp,vret,sizeof(char *)*MAX_NUMBER_POINTER*(count-1));
        free(vret);
        vret=(char **)tmp;
      }
    }
    closedir(dirp);
    end_loop:;
    r++;
  }
  /*when i go here len and item are reserve for make string*/
  vret[item]=0;
  return vret;
}

/*phần include ở trên và code ở trên*/

/*
  this is main 
*/
int main(){
  char **vpt=get_list_exec(0);
  int r=0;
  while(vpt[r]){
     printf("%s ",vpt[r]);
  }

}

/*find cmd in path and return malloc string */
char *which(const char *word){
  char **vpath=str2arword(getenv("PATH"),':');
  char buf[266],*rpt=0;
  size_t r=0;
  while(vpath[r]){
        strcpy(buf,vpath[r]);strcat(buf,"/");
        strcat(buf,word);
        if(access(buf,F_OK)==0) {
          rpt=(char *)malloc(strlen(buf));
          if(rpt)  strcpy(rpt,buf);
          return rpt;
        }
        r++;
  }
  free((void *)vpath);
  return NULL;
}