unix期末复习3.doc

函数1：path_alloc函数为路径名动态地分配空间/*这个跟版本关系很大*/#include apue.h #include #include #ifdef PATH_MAX /*如果定义了路径名的最大长度*/static int pathmax = PATH_MAX; /*将它赋予我们自己定义的变量pathmax*/#else static int pathmax = 0; /*否则该位置0*/#endif /*上面那个if结束*/#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)/*PATH_MAX相对路径名的最大字节数，包括null_PC_PATH_MAX*/ if (errno = 0) pathmax = PATH_MAX_GUESS; /* 确认是未决的就使用我们猜测的值 */ else /*errno不为0说明pathconf执行错误*/ err_sys(pathconf error for _PC_PATH_MAX); else pathmax+; /* 没有/说明是根目录，它也有一个路径 */ if (posix_version SUSV3) /*size和版本有关*/ size = pathmax + 1; else size = pathmax; if (ptr = malloc(size) = NULL) /*分配空间失败则返回空指针*/ err_sys(malloc error for pathname); if (sizep != NULL) *sizep = size; /*如果传入的参数不是null，说明它需要分配空间，把size分给它*/return(ptr); /*返回这段空间的首地址指针*/ 递归降序遍历目录层次结构，并按文件类型计数#include#include#include#include#includeourhdr.htypedefintMyfunc(const char *, const struct stat *, int);/* function type thats called for each filename */static Myfuncmyfunc;static intmyftw(char *, Myfunc *);static intdopath(Myfunc *);static longnreg, ndir, nblk, nchr, nfifo, nslink, nsock, ntot;intmain(int argc, char *argv)intret;if (argc != 2) /*输入的参数个数不为2，提醒输入的格式*/err_quit(usage: ftw );ret = myftw(argv1, myfunc);/* 解析整个完整的路径 */if ( (ntot = nreg + ndir + nblk + nchr + nfifo + nslink + nsock) = 0) /*一个文件也没有，这个类每个都是0*/ntot = 1; /*特殊技巧，分母为0，置1也无妨，只要非0即可 0/1=0*/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);exit(ret);/* * Descend through the hierarchy, starting at pathname. * The callers func() is called for every file. */#defineFTW_F1/* 不是目录的文件 */#defineFTW_D2/* 目录*/#defineFTW_DNR3/* 不可以读的文件 */#defineFTW_NS4/* 不能被stat的文件 */static char*fullpath; /* 包含每个文件的完整路径名 */static int /* 我们返回任何func()函数返回的*/myftw(char *pathname, Myfunc *func)fullpath = path_alloc(NULL);/这里采用默认的path_alloc大小*/*这里调用path_alloc函数，所以要gcc 2.c error.c path_alloc.c -o 2*/strcpy(fullpath, pathname); /不用像课本那样，strcpy自动在结束的位置补上/n /* 为fullpath变量初始化 */ return(dopath(func);/* * 通过层次进行下降操作，我们从全路径开始 * 如果是一个绝对的路径而非一个目录，我们调用lstat函数 * call func(), and return. For a directory, we call ourself * recursively for each name in the directory. */static int dopath(Myfunc* func)struct statstatbuf; /*statbuf是stat结构体的实例*/struct dirent*dirp; /*为获取文件夹目录所用的结构体*/DIR*dp; /*与目录有关的指针*/intret;char*ptr; /*保存要显示的字符串*/if (lstat(fullpath, &statbuf) d_name, .) = 0 | strcmp(dirp-d_name, .) = 0)continue; /*忽略.和.*/strcpy(ptr, dirp-d_name);/* append name after slash */if ( (ret = dopath(func) != 0)/* recursive */break;/* time to leave */ptr-1 = 0;/* erase everything from slash onwards */if (closedir(dp) 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(cant 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);3. lstat函数int lstat(const char *pathname, struct stat *buf); 文件类型用中说明的文件类型宏测试S_ISREG(mode) = 1正规文件(S_IFREG)S_ISDIR(mode) = 1目录文件(S_IFDIR)S_ISCHR(mode) = 1字符特殊文件(S_IFCHR)S_ISBLK(mode) = 1块特殊文件(S_IFBLK)S_ISFIFO(mode) = 1管道或FIFO文件(S_IFFIFO)S_ISLNK(mode) = 1符号链接(S_IFLNK)S_ISSOCK(mode) = 1套接口(S_IFSOCK)针对每个命令参数打印其文件类型#include#include#includeourhdr.hint main(int argc, char *argv)inti;struct statbuf;char*ptr;for (i = 1; i argc; i+) printf(%s: , argvi);if (lstat(argvi, &buf) 0) err_ret(lstat error);continue;if (S_ISREG(buf.st_mode)ptr = regular;else if (S_ISDIR(buf.st_mode)ptr = directory;else if (S_ISCHR(buf.st_mode)ptr = character special);else if (S_ISBLK(buf.st_mode)ptr