exer4.11.c(done)

//第一次把apue的課後習題做出來了，以作紀念。 PS：這個程式的已耗用時間比figure4.22的已耗用時間多，大概是由於切換當前工作目錄引起的吧

#include "apue.h"#include <dirent.h>#include <limits.h>   //line9-54 is copied from figure2.15#ifdef        PATH_MAXstatic int  pathmax = PATH_MAX;#elsestatic int  pathmax = 0;#endif #define SUSV3 200112L static long        posix_version = 0; /* If PATH_MAX is indeterminate, no guarantee this is adequate */#define     PATH_MAX_GUESS  1024 char *path_alloc(int *sizep) /* also return allocated size, if nonnull */{  char      *ptr;  int         size;   if (posix_version == 0)    posix_version = sysconf(_SC_VERSION);   if (pathmax == 0) {                 /* first time through */    errno = 0;    if ((pathmax = pathconf("/", _PC_PATH_MAX)) < 0) {      if (errno == 0)         pathmax = PATH_MAX_GUESS;       /* it's indeterminate */      else         err_sys("pathconf error for _PC_PATH_MAX");    } else {      pathmax++;          /* add one since it's relative to root */    }  }  if (posix_version < SUSV3)    size = pathmax + 1;  else    size = pathmax;   if ((ptr = malloc(size)) == NULL)    err_sys("malloc error for pathname");   if (sizep != NULL)    *sizep = size;  return(ptr);}  typedef int Myfunc(const char *, const struct stat *, int); static Myfunc myfunc;static int myftw(char *, Myfunc *); static long nreg, ndir, nblk, nchr, nfifo, nslink, nsock, ntot; intmain(int argc, char *argv[]){  int ret;   if(argc != 2)    err_quit("usage: %s <starting-pathname>", argv[0]);   ret = myftw(argv[1], myfunc);   ntot = nreg+ ndir+ nblk+ nchr+ nfifo+ nslink+ nsock;   if(ntot == 0)    ntot == 1;   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("symbolic links= %7ld, %5.2f %%\n", nslink, nslink*100.0/ntot);  printf("FIFOs         = %7ld, %5.2f %%\n", nfifo, nfifo*100.0/ntot);  printf("sockets       = %7ld, %5.2f %%\n", nsock, nsock*100.0/ntot);   exit(ret);} #define FTW_F 1#define FTW_D 2#define FTW_DNR 3#define FTW_NS 4 static int myftw(char *pathname, Myfunc *func){  struct stat statbuf;  struct dirent *dirp;  DIR *dp;  int ret;  char *ptr;   if(lstat(pathname, &statbuf) < 0)    return(func(pathname, &statbuf, FTW_NS));  if(S_ISDIR(statbuf.st_mode) == 0)    return(func(pathname, &statbuf, FTW_F));   if((ret = func(pathname, &statbuf, FTW_D)) < 0)    return(ret);   if(chdir(pathname) < 0)    err_sys("chdir to %s error", pathname);   if((dp = opendir(".")) == NULL)       //access deny    return(func(pathname, &statbuf, FTW_DNR));   while((dirp = readdir(dp)) != NULL){    if(strcmp(dirp->d_name, ".") == 0 || strcmp(dirp->d_name, "..") == 0)      continue;    if((ret = myftw(dirp->d_name, func)) != 0)      break;  }    chdir("..");   if(closedir(dp) < 0)    err_ret("can't close directory %s", pathname);  return(ret);}  static intmyfunc(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);    }    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);}