Source Code 1992 March/Source_Code_CD-ROM_Walnut_Creek_March_1992.iso/usenet/altsrcs/1/1359

Internet Message Format | 1990-12-28 | 7.6 KB

From: [e-mail] (Steve Friedl)
Newsgroups: alt.sources
Subject: [comp.unix.questions] Re: Tip about lost+found
Message-ID: <[e-mail]>
Date: 21 May 90 19:53:57 GMT

Archive-name: mklostandfound/21-May-90
Original-posting-by: [e-mail] (Steve Friedl)
Original-subject: Re: Tip about lost+found
Reposted-by: [e-mail] (Edward Vielmetti)

[This is an experimental alt.sources re-posting from the newsgroup(s)
comp.unix.questions. Comments on this service to [e-mail]
(Edward Vielmetti).]


> Otherwise you'll need
> to increase the number of slots in your lost+found directory (easily
> done by writing a script that creates a whole bunch of empty files in
> that directory and then deletes them again).

I make filesystems so often that I got tired of writing the
traditional shell script to make the lost+found directory, and in
the process I ended up writing a C program to do it faster.

It turns out that rather than creating a bunch of files, which
involves making lots of inodes, it is much faster to make one
file and then make lots of links to it.  When done this way, the
dominant operation is where it should be: writing directory
entries to extend lost+found.

I put this program (included shortly) in /etc/mkl+f and it has
proved to be really handy.  What I'd like to know is why in the
world doesn't mkfs build a populated lost+found when it makes
the filesystem?  It seems to me to be the ideal place for it
(at least by request with some command-line option).

Another tip: make your lost+found directory drwx------.
Otherwise, secret files that previously relied on protected
parent directories suddenly can find themselves out in the open.
A few packages (CrystalWriter, for instance), stick their trash
files in lost+found, so do this only if you know you can.

The program follows:

#---------------------------------- cut here -------------------------

/*
 * mkl+f.c
 *
 * written by :    Stephen J. Friedl
 *        Software Consultant
 *        Tustin, CA  92680
 *        uunet!mtndew!friedl
 *
 * Description:
 *
 *    This makes a lot of directory entries in the current directory.
 *    It starts by creat()ing the file ..000 and linking all the rest
 *    to it.  This method is over twice as fast as creat()ing the files
 *    one at a time.  This is because a creat() has to make an entire
 *    inode, while a link just updates the directory and one inode's
 *    link count.  All the files are removed when done.  The program
 *    exits on errors.
 *
 *    This program probably won't work on a BSD or SVR4.0 system.
 *
 *     ===NOTE=== This program is in the public domain and can be
 *    used by any person for any reason with no restrictions
 *    whatsoever.  Have fun, folks.
 *
 * HISTORY
 *     Tue Jan 28 23:22:53 PST 1986 by SJF
 *    > created
 */
#include    <stdio.h>
#include    <string.h>
#include    <fcntl.h>
#include    <errno.h>
#include    <sys/types.h>
#include    <sys/stat.h>

/*----------------------------------------------------------------------
 * this is the desired size of the lost+found directory
 */
#define        L_F_SIZE    (4*1024)    /* size of directory    */

#ifdef    __STDC__
#  include    <stdlib.h>
#  include    <stdarg.h>
#  define    Void        void
#  define    PROTO(name,args) name ( args )
#else
#  include    <varargs.h>
#  define    Void        char
#  define    const        /*nothing*/
#  define    PROTO(name,args) name ( )

extern char *malloc();
extern void exit();
#endif

#ifndef    EXIT_SUCCESS
#  define    EXIT_SUCCESS    0
#  define    EXIT_FAILURE    1
#endif

#define        fpr        (void)fprintf
#define        spr        (void)sprintf

/*----------------------------------------------------------------------
 * We keep a list of all files created here so we can remove them later.
 * We don't do any bounds checking when adding a new name to the list
 * because we statically allocate enough up front.
 */
#define        savefile(fname)        (FileTbl[Nfiles++] = strsave(fname))

static char const    *FileTbl[L_F_SIZE];    /* list of files    */
static int        Nfiles = 0;        /* # of elements in above */



static char const     *ProgName,        /* program name        */
            *LinkFile;        /* file to link to    */
static int        dot_fd;            /* fildes of current dir */

static PROTO(long dot_size, ( void ) );
static PROTO(char *strsave, ( char const * ) );
static PROTO(void die,        ( char const *, ... ) );

/*ARGSUSED*/
main(argc, argv)
int    argc;
char    *argv[];
{
int    i, fd;

    ProgName = argv[0];

    /*--------------------------------------------------------------
     * open the current directory so we can get the size quickly
     * without having to know the size of a directory entry (feature).
     */
    if (dot_fd = open(".", O_RDONLY), dot_fd < 0)
        die("can't open current directory (errno = %d)", errno);

    /*--------------------------------------------------------------
     * are we already done?
     */
    if (dot_size() >= L_F_SIZE)
        die("current directory is already large enough");

    /*--------------------------------------------------------------
     * first touch the first file and die on error.
     */
    LinkFile = "..000";

    if (fd = creat(LinkFile, 0), fd < 0)
        die("can't create initial file %s (errno = %d)", LinkFile);
    (void)close(fd);
    savefile(LinkFile);

    /*--------------------------------------------------------------
     * now loop while the size is not enough.  Before we make a
     * new link, make sure we're not trashing some current file.
     */
    while (dot_size() < L_F_SIZE)
    {
    char        buf[100];
    static int    counter = 0;

        spr(buf, "..%03d", counter++);
        if (file_exists(buf))
            continue;
        if (link(LinkFile, buf) != 0)
            die("can't link(\"%s\", \"%s\") (errno=%d)", LinkFile,
              buf, errno);
        savefile(buf);
    }
    (void)close(dot_fd);

    /*--------------------------------------------------------------
     * now clean up all the files we previously created.
     */
    for (i = 0; i < Nfiles; i++)
    {
    char const *fname = FileTbl[i];

        if (unlink(fname) != 0)
            die("can't unlink(\"%s\") - errno=%d", fname, errno);
    }

    exit(EXIT_SUCCESS);
    /* NOTREACHED */
}

/*
 * exists()
 *
 *    Given a filename, return TRUE if the file exists and
 *    FALSE if not.  If we're able to stat the file, we assume
 *    that the file exists...
 */
static int
file_exists(fname)
char const *fname;
{
struct stat    stbuf;

    return(stat(fname, &stbuf) == 0);
}

/*
 * strsave()
 *
 *    Given a string, save it into managed memory
 */
static char *
strsave(str)
char const *str;
{
char *p;

    if (p = malloc(strlen(str)+1), p == NULL)
        die("out of memory in strsave()");
    return(strcpy(p, str));
}

/*
 * dot_size()
 *
 *    Return the size of the current directory.  Die
 *    if we can't find it (this should never happen).
 */
static long
dot_size()
{
struct stat    stbuf;

    if (fstat(dot_fd, &stbuf) < 0)
        die("cannot stat current dir (errno = %d)", errno);
    return(stbuf.st_size);
}

/*
 * die()
 *
 *    Given a printf-style argument list, format a message to the
 *    standard error stream including the program name, then exit
 *    with a failure status
 */

#ifdef    __STDC__

static void
die(char const *format, ...)
{
va_list    args;

    (void)fprintf(stderr, "%s: ", ProgName);

    va_start(args, format);
    (void)vfprintf(stderr, format, args);
    va_end(args);

    (void)fputc('\n', stderr);
    exit(EXIT_FAILURE);
}

#else /*__STDC__*/

/*VARARGS*/
static void
die(va_alist)
va_dcl
{
va_list    args;
char    *format;

    (void)fprintf(stderr, "%s: ", ProgName);

    va_start(args);
    format = va_arg(args, char *);
    (void)vfprintf(stderr, format, args);
    va_end(args);

    (void)fputc('\n', stderr);
    exit(EXIT_FAILURE);
}

#endif     /* __STDC__ */

#---------------------------------- cut here -------------------------


--
Stephen J. Friedl, KA8CMY / Software Consultant / Tustin, CA / 3B2-kind-of-guy
[phone] voice   /   [e-mail]   /   {uunet,attmail}!mtndew!friedl

What's Spaf gonna do if Purdue hires RTM?