示例代码

#include "apue.h"
#include <dirent.h>
#include <limits.h>
#include <time.h>

/* function type that is called for each filename */
typedef    int    Myfunc(const char *, const struct stat *, int);

static Myfunc    myfunc;
static int        myftw(char *, Myfunc *);
static int        dopath(Myfunc *);

static long    nreg, ndir, nblk, nchr, nfifo, nslink, nsock, ntot;

int
main(int argc, char *argv[])
{
    int        ret;
    clock_t c_start,c_end;
    
    c_start = clock();

    if (argc != 2)
        err_quit("usage:  ftw  <starting-pathname>");

    ret = myftw(argv[1], myfunc);        /* does it all */

    ntot = nreg + ndir + nblk + nchr + nfifo + nslink + nsock;
    if (ntot == 0)
        ntot = 1;        /* avoid divide by 0; print 0 for all counts */
    printf("regular files  = %7ld, %5.2f %%/n", nreg,
      nreg*100.0/ntot);
    printf("directories    = %7ld, %5.2f %%/n", ndir,
      ndir*100.0/ntot);
    printf("block special  = %7ld, %5.2f %%/n", nblk,
      nblk*100.0/ntot);
    printf("char special   = %7ld, %5.2f %%/n", nchr,
      nchr*100.0/ntot);
    printf("FIFOs          = %7ld, %5.2f %%/n", nfifo,
      nfifo*100.0/ntot);
    printf("symbolic links = %7ld, %5.2f %%/n", nslink,
      nslink*100.0/ntot);
    printf("sockets        = %7ld, %5.2f %%/n", nsock,
      nsock*100.0/ntot);

    c_end = clock();
    printf("elapsed: %f seconds/n", (c_end-c_start)/(double)CLOCKS_PER_SEC); 
    exit(ret);
}

/*
 * Descend through the hierarchy, starting at "pathname".
 * The caller's func() is called for every file.
 */
#define    FTW_F    1        /* file other than directory */
#define    FTW_D    2        /* directory */
#define    FTW_DNR    3        /* directory that can't be read */
#define    FTW_NS    4        /* file that we can't stat */

static char    *fullpath;        /* contains full pathname for every file */

static char *filename; 

static int                    /* we return whatever func() returns */
myftw(char *pathname, Myfunc *func)
{
    int len;
    filename = path_alloc(&len); 
    fullpath = path_alloc(&len);    /* malloc's for PATH_MAX+1 bytes */
                                    /* ({Prog pathalloc}) */
    strncpy(fullpath, pathname, len);    /* protect against */
    fullpath[len-1] = 0;                /* buffer overrun */
    strcpy(filename,fullpath); 

    return(dopath(func));
}

/*
 * Descend through the hierarchy, starting at "fullpath".
 * If "fullpath" is anything other than a directory, we lstat() it,
 * call func(), and return.  For a directory, we call ourself
 * recursively for each name in the directory.
 */
static int                    /* we return whatever func() returns */
dopath(Myfunc* func)
{
    struct stat        statbuf;
    struct dirent    *dirp;
    DIR                *dp;
    int                ret;
    char            *ptr;

    if (lstat(filename , &statbuf) < 0)    /* stat error */
        return(func(fullpath, &statbuf, FTW_NS));
    if (S_ISDIR(statbuf.st_mode) == 0)    /* not a directory */
        return(func(fullpath, &statbuf, FTW_F));

    /*
     * It's a directory.  First call func() for the directory,
     * then process each filename in the directory.
     */
    if ((ret = func(fullpath, &statbuf, FTW_D)) != 0)
        return(ret);

    ptr = fullpath + strlen(fullpath);    /* point to end of fullpath */
    *ptr++ = '/';
    *ptr = 0;
    
    chdir(fullpath) ; /* set local work directory  */

    if ((dp = opendir(fullpath)) == NULL)    /* can't read directory */
        return(func(fullpath, &statbuf, FTW_DNR));

    while ((dirp = readdir(dp)) != NULL) {
        if (strcmp(dirp->d_name, ".") == 0  ||
            strcmp(dirp->d_name, "..") == 0)
                continue;        /* ignore dot and dot-dot */

        strcpy(ptr, dirp->d_name);    /* append name after slash */
        strcpy(filename,dirp->d_name); 
        if ((ret = dopath(func)) != 0)        /* recursive */
            break;    /* time to leave */
    }
    ptr[-1] = 0;    /* erase everything from slash onwards */
    chdir("..");  /* return to parent directory */

    if (closedir(dp) < 0)
        err_ret("can't close directory %s", fullpath);

    return(ret);
}

static int
myfunc(const char *pathname, const struct stat *statptr, int type)
{
    switch (type) {
    case FTW_F:
        switch (statptr->st_mode & S_IFMT) {
        case S_IFREG:    nreg++;        break;
        case S_IFBLK:    nblk++;        break;
        case S_IFCHR:    nchr++;        break;
        case S_IFIFO:    nfifo++;    break;
        case S_IFLNK:    nslink++;    break;
        case S_IFSOCK:    nsock++;    break;
        case S_IFDIR:
            err_dump("for S_IFDIR for %s", pathname);
                    /* directories should have type = FTW_D */
        }
        break;

    case FTW_D:
        ndir++;
        break;

    case FTW_DNR:
        err_ret("can't read directory %s", pathname);
        break;

    case FTW_NS:
        err_ret("stat error for %s", pathname);
        break;

    default:
        err_dump("unknown type %d for pathname %s", type, pathname);
    }

    return(0);
}