minix/lib/nbsd_libcompat_minix/mtab.c

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/* This package consists of 4 routines for handling the /etc/mtab file.
* The /etc/mtab file contains information about the root and mounted file
* systems as a series of lines, each one with exactly four fields separated
* by one space as follows:
*
* special mounted_on version rw_flag
*
* where
* special is the name of the block special file
* mounted_on is the directory on which it is mounted
* version is either 1 or 2 for MINIX V1 and V2 file systems
* rw_flag is rw or ro for read/write or read only
*
* An example /etc/mtab:
*
* /dev/ram / 2 rw
* /dev/hd1 /usr 2 rw
* /dev/fd0 /user 1 ro
*
*
* The four routines for handling /etc/mtab are as follows. They use two
* (hidden) internal buffers, mtab_in for input and mtab_out for output.
*
* load_mtab(&prog_name) - read /etc/mtab into mtab_in
* get_mtab_entry(&s1, &s2, &s3, &s4) - arrays that are filled in
* put_mtab_entry(&s1, &s2, &s3, &s4) - append a line to mtab_out
* rewrite_mtab(&prog_name) - write mtab_out to /etc/mtab
*
* If load_mtab and rewrite_mtab work, they return 0. If they fail, they
* print their own error messages on stderr and return -1. When get_mtab_entry
* runs out of entries to return, it sets the first pointer to NULL and returns
* -1 instead of 0. Also, rewrite_mtab returns -1 if it fails.
*/
#include <sys/types.h>
#include <minix/minlib.h>
#include <ctype.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#define BUF_SIZE 512 /* size of the /etc/mtab buffer */
char *etc_mtab = "/etc/mtab"; /* name of the /etc/mtab file */
static char mtab_in[BUF_SIZE+1]; /* holds /etc/mtab when it is read in */
static char mtab_out[BUF_SIZE+1]; /* buf to build /etc/mtab for output later */
static char *iptr = mtab_in; /* pointer to next line to feed out. */
static char *optr = mtab_out; /* pointer to place where next line goes */
_PROTOTYPE(int load_mtab, (char *prog_name ));
_PROTOTYPE(int rewrite_mtab, (char *prog_name ));
_PROTOTYPE(int get_mtab_entry, (char *special, char *mounted_on,
char *version, char *rw_flag));
_PROTOTYPE(int put_mtab_entry, (char *special, char *mounted_on,
char *version, char *rw_flag));
_PROTOTYPE(void err, (char *prog_name, char *str ));
int load_mtab(prog_name)
char *prog_name;
{
/* Read in /etc/mtab and store it in /etc/mtab. */
int fd, n;
char *ptr;
/* Open the file. */
fd = open(etc_mtab, O_RDONLY);
if (fd < 0) {
err(prog_name, ": cannot open ");
return(-1);
}
/* File opened. Read it in. */
n = read(fd, mtab_in, BUF_SIZE);
if (n <= 0) {
/* Read failed. */
err(prog_name, ": cannot read ");
return(-1);
}
if (n == BUF_SIZE) {
/* Some nut has mounted 50 file systems or something like that. */
std_err(prog_name);
std_err(": file too large: ");
std_err(etc_mtab);
return(-1);
}
close(fd);
/* Replace all the whitespace by '\0'. */
ptr = mtab_in;
while (*ptr != '\0') {
if (isspace(*ptr)) *ptr = '\0';
ptr++;
}
return(0);
}
int rewrite_mtab(prog_name)
char *prog_name;
{
/* Write mtab_out to /etc/mtab. */
int fd, n;
/* Do a creat to truncate the file. */
fd = creat(etc_mtab, 0777);
if (fd < 0) {
err(prog_name, ": cannot overwrite ");
return(-1);
}
/* File created. Write it. */
n = write(fd, mtab_out, (unsigned int)(optr - mtab_out));
if (n <= 0) {
/* Write failed. */
err(prog_name, " could not write ");
return(-1);
}
close(fd);
return(0);
}
int get_mtab_entry(special, mounted_on, version, rw_flag)
char *special;
char *mounted_on;
char *version;
char *rw_flag;
{
/* Return the next entry from mtab_in. */
if (iptr >= &mtab_in[BUF_SIZE]) {
special[0] = '\0';
return(-1);
}
strcpy(special, iptr);
while (isprint(*iptr)) iptr++;
while (*iptr == '\0'&& iptr < &mtab_in[BUF_SIZE]) iptr++;
strcpy(mounted_on, iptr);
while (isprint(*iptr)) iptr++;
while (*iptr == '\0'&& iptr < &mtab_in[BUF_SIZE]) iptr++;
strcpy(version, iptr);
while (isprint(*iptr)) iptr++;
while (*iptr == '\0'&& iptr < &mtab_in[BUF_SIZE]) iptr++;
strcpy(rw_flag, iptr);
while (isprint(*iptr)) iptr++;
while (*iptr == '\0'&& iptr < &mtab_in[BUF_SIZE]) iptr++;
return(0);
}
int put_mtab_entry(special, mounted_on, version, rw_flag)
char *special;
char *mounted_on;
char *version;
char *rw_flag;
{
/* Append an entry to the mtab_out buffer. */
int n1, n2, n3, n4;
n1 = strlen(special);
n2 = strlen(mounted_on);
n3 = strlen(version);
n4 = strlen(rw_flag);
if (optr + n1 + n2 + n3 + n4 + 5 >= &mtab_out[BUF_SIZE]) return(-1);
strcpy(optr, special);
optr += n1;
*optr++ = ' ';
strcpy(optr, mounted_on);
optr += n2;
*optr++ = ' ';
strcpy(optr, version);
optr += n3;
*optr++ = ' ';
strcpy(optr, rw_flag);
optr += n4;
*optr++ = '\n';
return(0);
}
void
err(prog_name, str)
char *prog_name, *str;
{
std_err(prog_name);
std_err(str);
std_err(etc_mtab);
perror(" ");
}