inotify/rand_dtree.c

This is inotify/rand_dtree.c, an example to accompany the book, The Linux Programming Interface.

This file is not printed in the book; it is a supplementary file for Chapter 19.

The source code file is copyright 2022, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.

 

Download inotify/rand_dtree.c

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Function list (Bold in this list means a function is not static)

/* rand_dtree.c

   A test program to use in conjunction with inotify_dtree.c.

   This program randomly creates, deletes, or renames
   subdirectories underneath the pathname specified in its
   sole command-line argument.
*/
#if ! defined(_XOPEN_SOURCE) || _XOPEN_SOURCE < 700
#undef _XOPEN_SOURCE
#define _XOPEN_SOURCE 500
#endif
#include <stdarg.h>
#include <limits.h>
#include <ftw.h>
#include "tlpi_hdr.h"

#define DLIM 60

/* Hack! We can't pass arguments to the function invoked by nftw(),
   so we use these global variables to exchange information with
   the function */

static int dcnt;
static char **dirList = NULL;
static int dlSize = 0;
static const int D_INCR = 1000;
static int
traverseTree(const char *pathname, const struct stat *sb, int tflag,
             struct FTW *ftwbuf)
{
    if (! S_ISDIR(sb->st_mode))
        return 0;

    //printf("%s\n", pathname);

    if (dcnt >= dlSize) {
        dlSize += D_INCR;
        dirList = realloc(dirList, dlSize * sizeof(char *));
        if (dirList == NULL)
            errExit("realloc");
    }

    dirList[dcnt] = strdup(pathname);

    dcnt++;

    return 0;
}
static int
getDirList(const char *pathname)
{
    dcnt = 0;

    if (nftw(pathname, traverseTree, 20, FTW_PHYS) == -1)
        errMsg("nftw: %s", pathname);

    return dcnt;
}

static FILE *logfp = NULL;
static void
logMessage(const char *format, ...)
{
    va_list argList;

    va_start(argList, format);

    if (logfp != NULL)
        vfprintf(logfp, format, argList);

    va_end(argList);
}
static void
usageError(char *pname)
{
    fprintf(stderr, "Usage: %s [options] dirpath {c|d|m}\n\n", pname);
    fprintf(stderr, "Perform random operations in the "
            "directory tree 'dirpath'\n");
    fprintf(stderr, "    c == create directories\n");
    fprintf(stderr, "    d == delete directories\n");
    fprintf(stderr, "    m == rename directories\n\n");
    fprintf(stderr, "Options:\n");
    fprintf(stderr, "    -l logfile     Record activity in log file\n");
    fprintf(stderr, "    -m maxops      Do at most 'maxops' operations "
            "(default is unlimited)\n");
    fprintf(stderr, "    -s usecs       Sleep 'usecs' microseconds "
            "between each operation\n");
    fprintf(stderr, "    -z stopfile    Immediately stop when the file "
            "'stopfile' is created\n");
    exit(EXIT_FAILURE);
}

#define MARKER_STRING "--"
int
main(int argc, char *argv[])
{
    srandom(0);

    char *stopFile = NULL;
    int maxops = 0;
    int usecs = 1;
    int opt;
    while ((opt = getopt(argc, argv, "l:m:s:z:")) != -1) {
        switch (opt) {
        case 's':
            usecs = atoi(optarg);
            break;

        case 'z':
            stopFile = optarg;
            break;

        case 'm':
            maxops = atoi(optarg);
            break;

        case 'l':
            logfp = fopen(optarg, "w+");
            if (logfp == NULL)
                errExit("fopen");
            setbuf(logfp, NULL);
            break;

        default:
            usageError(argv[0]);
        }
    }

    if (optind + 1 >= argc)
        usageError(argv[0]);

    int opcnt = 0;

    for (;;) {
        getDirList(argv[optind]);

        int nslashes;
        char *to_move;
        char path[PATH_MAX];

        switch (argv[optind + 1][0]) {
        case 'c':
            snprintf(path, sizeof(path), "%s/%ld%s%s_%d",
                    dirList[random() % dcnt],
                    (long) getpid() % 100, MARKER_STRING, "cr", opcnt);
            if (strlen(path) > DLIM)
                continue;
            nslashes = 0;
            for (char *p = path; *p; p++)
                if (*p == '/')
                    nslashes++;

            if (nslashes > 1)
                if (random() % nslashes > 0)
                    continue;

            if (mkdir(path, 0700) == 0)
                logMessage("mkdir: %s\n", path);

            int scnt = 1;
            while ((random() % 3) < 2) {
                char spath[PATH_MAX];

                int s = snprintf(spath, sizeof(path), "%s/%ld%s%s%d_%d", path,
                        (long) getpid() % 100,
                        MARKER_STRING, "scr", scnt, opcnt);
                if (s > DLIM)
                    break;

                if (mkdir(spath, 0700) == 0)
                    logMessage("mkdir: %s\n", spath);

                strncpy(path, spath, PATH_MAX);
                path[PATH_MAX - 1] = '\0';
                scnt++;
            }
            break;

        case 'd':
            if (dcnt == 0)
                continue;

            snprintf(path, sizeof(path), "%s", dirList[random() % dcnt]);
            while (strstr(path, MARKER_STRING) != NULL) {

                if (rmdir(path) == -1)
                    break;
                logMessage("rmdir: %s\n", path);

                char *p = strrchr(path, '/');
                if (p == NULL)
                    break;

                *p = '\0';
            }
            break;

        case 'm':
            if (dcnt < 3)
                continue;

            to_move = dirList[random() % dcnt];

            if (strstr(to_move, MARKER_STRING) != NULL) {
                char tfile[PATH_MAX];

                char *p = strrchr(to_move, '/');
                snprintf(tfile, sizeof(tfile), "%s", p + 1);
                p = strstr(tfile, "__ren");
                if (p != NULL)
                    *p = '\0';

                char target[PATH_MAX];
                int s = snprintf(target, sizeof(target), "%s/%s__ren%04d-%ld",
                                dirList[random() % dcnt],
                                tfile, opcnt, (long) getpid());

                if (s > DLIM)
                    break;

                if (rename(to_move, target) == 0)
                    logMessage("rename: %s ==> %s\n", to_move, target);
            }

            break;
        }

        for (int j = 0; j < dcnt; j++) {
            free(dirList[j]);
            dirList[j] = NULL;
        }

        opcnt++;

        usleep(usecs);

        if (maxops > 0 && opcnt >= maxops)
            break;

        if (access(stopFile, F_OK) == 0)
            break;
    }

    exit(EXIT_SUCCESS);
}

 

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