list files

#include <apue.h>#include <dirent.h>int main( int argc, char *argv[] ){DIR* dp,*dp2;char* argv2[2];char buff[512];struct dirent *dirp;if(argc!=2){   printf( "usage:ls directory_name\n" );   return 0;}if((dp=opendir(argv[1]))==NULL){   printf("can't open %s",argv[1]);   return 0;}while((dirp=readdir(dp))!=NULL){if(strcmp(".",dirp->d_name)==0 || strcmp("..",dirp->d_name)==0)   continue;sprintf(buff,"%s/%s",argv[1],dirp->d_name);if((dp2=opendir(buff))!=NULL){closedir(dp2);argv2[0]=NULL;argv2[1]=buff;main(2,argv2);}else  printf("%s\n",buff);}closedir(dp);return 0;}