Directory reading!

how do i execute this file in linux!

Code:

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#include <sys/types.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>        /* for major and minor */
#include <unistd.h>                /* for readlink */
#include <time.h>                  /* for ctime */
#include <dirent.h>
#include <stdio.h>

char typeOfFile(mode_t);
char *permOfFile(mode_t);
void outputStatInfo(char *, char *, struct stat *);

int 
main(int argc, char **argv)
{
  DIR *dp;
  char *dirname;
  struct stat st;
  struct dirent *d;
  char filename[BUFSIZ+1];

  /*
  * For each directory on the command line ...
  */
  while (--argc) {
    dirname = *++argv;


    /*
    * Open the directory.
    */
    if ((dp = opendir(dirname)) == NULL) {
      perror(dirname);
      continue;
    }

    printf("%s:\n", dirname);

    /*
    * For each file in the directory...
    */
    while ((d = readdir(dp)) != NULL) {
      /*
      * Create the full file name.
      */
      sprintf(filename, "%s/%s", dirname, d->d_name);

      /*
      * Find out about it.
      */
      if(lstat(filename, &st) < 0) {
        perror(filename);
        putchar('\n');
        continue;
      }

      /*
      * Print out the information.
      */
      outputStatInfo(filename, d->d_name, &st);
      putchar('\n');
    }
    putchar('\n');
    closedir(dp);
  }
  exit(0);
}

/*
 * outputStatInfo - print out the contents of the stat structure.
 */
void outputStatInfo(char *pathname, char *filename, struct stat *st)
{
  int n;
  char slink[BUFSIZ+1];

  /*
  * Print the number of file system blocks, permission bits,
  * number of links, user-id, and group-id.
  */
  printf("%5d ", st->st_blocks);
  printf("%c%s ", typeOfFile(st->st_mode), permOfFile(st->st_mode));
  printf("%3d ", st->st_nlink);
  printf("%5d/%-5d ", st->st_uid, st->st_gid);

  /*
  * If the file is not a device, print its size; otherwise
  * print its major and minor device numbers.
  */
  if (((st->st_mode & S_IFMT) != S_IFCHR) &&
      ((st->st_mode & S_IFMT) != S_IFBLK))
    printf("%9d ", st->st_size);
  else
    printf("%4d,%4d ", major(st->st_rdev), minor(st->st_rdev));

  /*
  * Print the access time.  The ctime() function is
  * described in Chapter 7, "Time of Day Operations."
  */
  printf("%.12s ", ctime(&st->st_mtime) + 4);

  /*
  * Print the file name.  If it's a symbolic link, also print
  * what it points to.
  */
  printf("%s", filename);

  if ((st->st_mode & S_IFMT) == S_IFLNK) {
    if ((n = readlink(pathname, slink, sizeof(slink))) < 0)
      printf(" -> ???");
    else
      printf(" -> %.*s", n, slink);
  }
}

/*
 * typeOfFile - return the letter indicating the file type.
 */
char
typeOfFile(mode_t mode)
{void outputStatInfo(char *pathname, char *filename, struct stat *st)
{
  int n;
  char slink[BUFSIZ+1];

  switch (mode & S_IFMT) {
  case S_IFREG:
    return('-');
  case S_IFDIR:
    return('d');
  case S_IFCHR:
    return('c');
  case S_IFBLK:
    return('b');
  case S_IFLNK:
    return('l');
  case S_IFIFO:
    return('p');
  case S_IFSOCK:
    return('s');
  }

  return('?');
}

/*
 * permOfFile - return the file permissions in an "ls"- like string.
 */
char *
permOfFile(mode_t mode)
{
  int i;
  char *p;
  static char perms[10];

  p = perms;
  strcpy(perms, "---------");

  /*
  * The permission bits are three sets of three bits: user
  * read/write/exec, group read/write/exec, other read=write/exec.  We
  * deal with each set of three bits in one pass through the loop.
  */
  for (i=0; i < 3; i++) {
    if (mode & (S_IREAD >> i*3))
      *p ='r';
    p++;

    if (mode & (S_IWRITE >> i*3))
      *p='w';
    p++;
    if (mode & (S_IEXEC >> i*3))
      *p = 'x';
    p++;
  }

  /*
  * Put special codes in for set-user-id, set-group-id,
  * and the sticky bit. ( This part is incomplete; "ls"
  * uses some other letters as well for cases such as
  * set-user-id bit without execute bit, and so forth.)
  */
  if ((mode & S_ISUID) !=0)
    perms[2] = 's';

  if ((mode & S_ISGID) !=0)
    perms[5] = 's';

  if ((mode & S_ISVTX) !=0)
    perms[8] = 't';

  return(perms);
}
}

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