lib/libcompat_minix/mtab.c

   1 /* This package consists of 4 routines for handling the /etc/mtab file.
   2  * The /etc/mtab file contains information about the root and mounted file
   3  * systems as a series of lines, each one with exactly four fields separated
   4  * by one space as follows:
   5  *
   6  *      special mounted_on version rw_flag
   7  *
   8  * where
   9  *      special is the name of the block special file
  10  *      mounted_on is the directory on which it is mounted
  11  *      version is either 1 or 2 for MINIX V1 and V2 file systems
  12  *      rw_flag is rw or ro for read/write or read only
  13  *
  14  * An example /etc/mtab:
  15  *
  16  *      /dev/ram / 2 rw
  17  *      /dev/hd1 /usr 2 rw
  18  *      /dev/fd0 /user 1 ro
  19  *
  20  *
  21  * The four routines for handling /etc/mtab are as follows.  They use two
  22  * (hidden) internal buffers, mtab_in for input and mtab_out for output.
  23  *
  24  *      load_mtab(&prog_name)              - read /etc/mtab into mtab_in
  25  *      get_mtab_entry(&s1, &s2, &s3, &s4) - arrays that are filled in
  26  *
  27  * If load_mtab works, it returns 0.  If it fails, it prints its own error
  28  * message on stderr and returns -1.  When get_mtab_entry
  29  * runs out of entries to return, it sets the first pointer to NULL and returns
  30  * -1 instead of 0.
  31  */
  32
  33 #include <sys/types.h>
  34 #include <lib.h>
  35 #include <minix/minlib.h>
  36 #include <ctype.h>
  37 #include <fcntl.h>
  38 #include <stdlib.h>
  39 #include <string.h>
  40 #include <unistd.h>
  41 #include <stdio.h>
  42
  43 #define BUF_SIZE   512            /* size of the /etc/mtab buffer */
  44
  45 char *etc_mtab = "/etc/mtab";     /* name of the /etc/mtab file */
  46 static char mtab_in[BUF_SIZE+1];  /* holds /etc/mtab when it is read in */
  47 static char *iptr = mtab_in;      /* pointer to next line to feed out. */
  48
  49 int load_mtab(char *prog_name);
  50 int get_mtab_entry(char dev[PATH_MAX], char mount_point[PATH_MAX],
  51         char type[MNTNAMELEN], char flags[MNTFLAGLEN]);
  52 static void err(char *prog_name, const char *str);
  53
  54
  55 int load_mtab(char *prog_name)
  56 {
  57 /* Read in /etc/mtab and store it in /etc/mtab. */
  58
  59   int fd, n;
  60   char *ptr;
  61
  62   /* Open the file. */
  63   fd = open(etc_mtab, O_RDONLY);
  64   if (fd < 0) {
  65         err(prog_name, ": cannot open ");
  66         return(-1);
  67   }
  68
  69   /* File opened.  Read it in. */
  70   n = read(fd, mtab_in, BUF_SIZE);
  71   if (n <= 0) {
  72         /* Read failed. */
  73         err(prog_name, ": cannot read ");
  74         return(-1);
  75   }
  76   if (n == BUF_SIZE) {
  77         /* Some nut has mounted 50 file systems or something like that. */
  78         std_err(prog_name);
  79         std_err(": file too large: ");
  80         std_err(etc_mtab);
  81         return(-1);
  82   }
  83
  84   close(fd);
  85
  86   ptr = mtab_in;
  87
  88   return(0);
  89 }
  90
  91 int get_mtab_entry(char dev[PATH_MAX], char mount_point[PATH_MAX],
  92                         char type[MNTNAMELEN], char flags[MNTFLAGLEN])
  93 {
  94 /* Return the next entry from mtab_in. */
  95
  96   int r;
  97
  98   if (iptr >= &mtab_in[BUF_SIZE]) {
  99         dev[0] = '\0';
 100         return(-1);
 101   }
 102
 103   r = sscanf(iptr, "%s on %s type %s (%[^)]s\n",
 104                 dev, mount_point, type, flags);
 105   if (r != 4) {
 106         dev[0] = '\0';
 107         return(-1);
 108   }
 109
 110   iptr = strchr(iptr, '\n');    /* Find end of line */
 111   if (iptr != NULL) iptr++;     /* Move to next line */
 112   return(0);
 113
 114 }
 115
 116 static void err(char *prog_name, const char *str)
 117 {
 118   std_err(prog_name);
 119   std_err(str);
 120   std_err(etc_mtab);
 121   perror(" ");
 122 }