/* umount - unmount a file system		Author: Andy Tanenbaum */
/*
   06/13/1994 - Claudio Tantignone.
   Modification to take block device or moount point via convertion with
   mtab table.

   09/14/2000 - Claudio Tantignone.
   Solve pointer compilation with strstr() function under Minix 2.0.2
*/

/* 
   Compile as:

   # cc -wa -o umount umount.c
   # chmem =32768 umount
*/

#define _POSIX_SOURCE
#define _MINIX
/* #define DEBUG */

#include <sys/types.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/stat.h>

#define BUFSIZE 1024
#define NOCONVERT 0
#define CONVERT   1
#define BAD       2

extern int errno;
extern char *strchr();

char *mounttable = "/etc/mtab";
char buffer[BUFSIZE], *p = &buffer[0], *q;
char dev[BUFSIZE];           /* device to be unmounted */

main(argc, argv)
int argc;
char *argv[];
{
  int flag = NOCONVERT;            /* flag to print convertion */

  if (argc != 2) usage();

  flag = parse(argv[1],dev);      /* parse device name or mount point */
  if (flag == BAD) {
     std_err(argv[1]);
     std_err(" : invalid umount point\n");
     exit(EINVAL);
     }

#ifdef DEBUG
  printf("parse device is %s\n", dev);
#endif

  if (umount(dev) < 0) {
	if (errno == EINVAL)
		std_err("Device not mounted\n");
	else
		perror("umount");
	exit(errno);
  }

  std_err(argv[1]);

  if (flag) {         /* check if is necesary to print more info */
     std_err(" (");
     std_err(dev);
     std_err(")");
     }

  std_err(" unmounted\n");
  do_mtab(dev);
  exit(0);
}

do_mtab(devname)
char *devname;
{
/* Remove an entry from mtab. */
  int n, fd;
  char line[256];

  p = &buffer[0];

  /* Read in the mount table and then overwrite the file. */
  fd = open(mounttable, O_RDWR);
  n = read(fd, buffer, BUFSIZE);
  close(fd);
  q = &buffer[n];
  fd = creat(mounttable, 0554);

  n = strlen(devname);
  while (getline(line) != 0) {
	if (strncmp(line, devname, n) == 0) continue;
	write(fd, line, strlen(line));
  }
}

int getline(ptr)
char *ptr;
{
  char c;

  while (p < q) {
	c = *p++;
	*ptr++ = c;
	if (c == '\n') {
		*ptr++ = 0;
		return(1);
	}
  }
  return(0);
}


usage()
{
  std_err("Usage: umount special [mount-point]\n");
  exit(1);
}

parse(in,out) /* parse mount point or device to device */
char *in;     /* device or mount point to be umounted */
char *out;    /* physical device to be umounted */
{
  struct stat st;       /* device struct */
  int n, fd, s, l;
  char line[256];

#ifdef DEBUG
   printf("stat for file %s\n", in);
#endif
   if (stat(in,&st) == -1) {
      perror("stat");
      exit(errno);
      }

#ifdef DEBUG
   printf("check mode for %s, mode %o \n", in,st.st_mode);
#endif
   if ((st.st_mode&S_IFBLK) == S_IFBLK) { /* if directly give device */
#ifdef DEBUG
      printf("%s is block device \n", in);
#endif
      strcpy(out,in);           /* copy device name and return */
      return(NOCONVERT);
      }

   /* here must check into mtab to convert mount point to device */
   /* Read in the mount table  */
#ifdef DEBUG
   printf("reading mtab ...\n");
#endif
   fd = open(mounttable, O_RDONLY);
   n = read(fd, buffer, BUFSIZE);
   close(fd);
   q = &buffer[n];
   n = strlen(in);
   s = BAD;
#ifdef DEBUG
   printf("searching for %s ...\n",in);
#endif
   while (getline(line) != 0) {
#ifdef DEBUG
        printf("line : %s",line);
#endif
      l = strlen(line);
/*      if (strstr(line, in) != ((char *) 0)) { */
      if (strstr(line, in) != 0) {
#ifdef DEBUG
          printf("%s founded in mtab.\n",in);
#endif
          s = CONVERT;  
          /* take from origin of line the device name and copy it */
          q = strchr(line,(int)' ');  /* get end position */
          *q = '\0';
          strcpy(out,line);
          break;
          }
      }
  return(s);
}