/* -*- Mode:C; Coding:us-ascii-unix; fill-column:132 -*- */
   @file      fileData.c
   @author    Mitch Richling <https://www.mitchr.me/>
   @Copyright Copyright 1995 by Mitch Richling.  All rights reserved.
   @brief     How to get file, and file system, information in UNIX.@EOL
   @Keywords  UNIX shell environment variable
   @Std       ISOC POSIX
              - Solaris 2.8
              - MacOS X.2
              - Linux (RH 7.3)

   This C program is intended to illustrate how query and manipulate file meta data like access/modify times, ownership, and

#include <stdio.h>              /* I/O lib         C89   */
#include <string.h>             /* Strings         C89   */
#include <sys/types.h>          /* UNIX types      POSIX */
#include <dirent.h>             /* UNIX dirs       POSIX */
#include <errno.h>              /* error stf       POSIX */
#include <utime.h>              /* utime           POSIX */
#include <sys/stat.h>           /* UNIX stat       POSIX */
#include <time.h>               /* time            C89   */
#include <unistd.h>             /* UNIX std stf    POSIX */
#include <stdlib.h>             /* Standard Lib    C89   */

int main(int argc, char *argv[]) {
  struct stat s;
  char readlinkBuf[1024];
  int readlinkChCnt;

  /* Make sure we have precisely one argument. */
  if(argc != 2) {
    printf("ERROR: One argument required.\n");
  } /* end if */

  printf("File name: %s\n", argv[1]);

  /* Stat the file given on the command line. */
  if(lstat(argv[1], &s) < 0) {
    printf("ERROR: fileData");
  } /* end if */

  printf("File inode number: %lu\n",                (unsigned long)s.st_ino);
  printf("Device number: %lu\n",                    (unsigned long)s.st_dev);
  printf("Device type: %lu\n",                      (unsigned long)s.st_rdev);
  printf("File mode: %lu\n",                        (unsigned long)s.st_mode);
  printf("File owner(UID): %lu\n",                  (unsigned long)s.st_uid);
  printf("File group owner(GID): %lu\n",            (unsigned long)s.st_gid);
  printf("File size: %lu bytes\n",                  (unsigned long)s.st_size);
  printf("File size: %lu blocks\n",                 (unsigned long)s.st_blocks);         /* WARNING: Wonky on some systems. */
  printf("Block size: %lu bytes\n",                 (unsigned long)s.st_blksize);        /* WARNING: Wonky on some systems. */
  printf("Block storage requirements: %lu bytes\n", (unsigned long)(512 * s.st_blocks)); /* WARNING: Wonky on some systems. */
  printf("File atime: %lu\n",                       (unsigned long)s.st_atime);
  printf("File ctime: %lu\n",                       (unsigned long)s.st_ctime);
  printf("File mtime: %lu\n",                       (unsigned long)s.st_mtime);
#ifdef BSD
  printf("File generation number: %lu\n",           (unsigned long)s.st_gen);

  /* WARNING: These constants didn't appear in POSIX till POSIX.1-2001, but the subset here was widely used even in the 1990s. */
  printf("File Type: ");
  if(s.st_mode & S_IFLNK)   printf(" symbolic link\n");
  else if(s.st_mode & S_IFSOCK)  printf(" socket\n");
#ifdef BSD
  else if(s.st_mode & S_IFWHT)   printf(" whiteout\n");
  else if(s.st_mode & S_IFIFO)   printf(" named pipe (fifo)\n");
  else if(s.st_mode & S_IFCHR)   printf(" character special\n");
  else if(s.st_mode & S_IFDIR)   printf(" directory\n");
  else if(s.st_mode & S_IFBLK)   printf(" block special\n");
  else if(s.st_mode & S_IFREG)   printf(" regular\n");
  else                           printf(" UNKNOWN\n");

  /* This section IS POSIX.*/
  if(S_ISDIR(s.st_mode))  printf("Macro check: directory\n");
  if(S_ISCHR(s.st_mode))  printf("Macro check: char special\n");
  if(S_ISBLK(s.st_mode))  printf("Macro check: block special\n");
  if(S_ISREG(s.st_mode))  printf("Macro check: regular file\n");
  if(S_ISFIFO(s.st_mode)) printf("Macro check: fifo or socket\n");

  /* WARNING: S_ISLNK started life in System V, and didn't make it into POSIX till POSIX.1-2001 */
  /* WARNING: S_ISSOCK appeared in POSIX.1-2001 */
  if(S_ISLNK(s.st_mode))  printf("Macro check: symbolic link\n");
  if(S_ISSOCK(s.st_mode)) printf("Macro check: socket\n");

  /* WARNING: Older systems may only return info for st_size and the file-type part of st_mode for symbolic links.  POSIX-2008
     fixed this problem, and requires lstat() to return information for everything except the the permission bits in st_mode */

  printf("File Permissions: \n");
  if(s.st_mode & S_ISUID)   printf(" set user id on execution\n");
  if(s.st_mode & S_ISGID)   printf(" set group id on execution\n");
  if(s.st_mode & S_ISVTX)   printf(" sticky bit\n");

  printf("owner permissions: ");
  if(s.st_mode & S_IRUSR)   printf(" read ");
  if(s.st_mode & S_IWUSR)   printf(" write");
  if(s.st_mode & S_IXUSR)   printf(" execute/search");

  printf("group permissions: ");
  if(s.st_mode & S_IRGRP)   printf(" read ");
  if(s.st_mode & S_IWGRP)   printf(" write");
  if(s.st_mode & S_IXGRP)   printf(" execute/search");

  printf("world permissions: ");
  if(s.st_mode & S_IROTH)   printf(" read ");
  if(s.st_mode & S_IWOTH)   printf(" write");
  if(s.st_mode & S_IXOTH)   printf(" execute/search");
  /* WARNING: The function readlink appeared in BSD sometime around 4.2, but didn't show in POSIX until POSIX.1-2001.  When it
     became part of POSIX, the return type changed to ssize_t.  Also see the warning about S_ISLNK above. */
  if(S_ISLNK(s.st_mode)) {
    if( (readlinkChCnt = readlink(argv[1], readlinkBuf, 1000)) < 0) {
      printf("ERROR: readlink failure.\n");
    } else {
      printf("File len: %d\n", readlinkChCnt);
      if(readlinkChCnt >= 0) {
        readlinkBuf[readlinkChCnt] = '\0';
        printf("Link target: %s\n", readlinkBuf);
      } /* end if */
    } /* end if/else */
  } /* end if */

  return 0;
} /* end func main */