《unix環境高階程式設計》--- 檔案和目錄
阿新 • • 發佈：2019-01-24
對每個命令函引數列印檔案型別
#include "apue.h"
int main(int argc, char *argv[])
{
int i;
struct stat buf;
char *ptr;
for(i=1; i<argc; i++)
{
printf("%s: ", argv[i]);
/*
int lstat(const char *restrict pathname, struct stat *restrict buf);
返回改符號連結的有關資訊
struct stat
{
mode_t st_mode; file 
access函式例項
#include "apue.h"
#include <fcntl.h>
int main(int argc, char *argv[])
{
if(argc != 2)
err_quit("usage: a.out <pathname>");
/*
int access(const char *pathname, int mode);
按實際使用者ID和實際組ID進行訪問許可權測試
mode:
R_OK 測試讀許可權
W_OK 測試寫許可權
X_OK 測試執行許可權
F_OK 測試檔案是否存在
*/
if(access(argv[1], R_OK)< 0)
err_ret("access error for %s", argv[1]);
else
printf("read access OK\n");
/*
open按程序的有效使用者ID和有效組ID程序訪問許可權測試
*/
if(open(argv[1], O_RDONLY) < 0)
err_ret("open error fo %s", argv[1]);
else
printf("open for reading OK\n");
exit(0);
}
umask函式例項
#include "apue.h"
#include <fcntl.h>
#define RWRWRW (S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH)
int main(void)
{
/*
mode_t umask(mode_t cmask);
為程序設定“檔案模式建立”遮蔽字，並返回以前的值
*/
umask(0);
if(creat("foo", RWRWRW) < 0)
err_sys("create error for foo");
/* 禁止所有組和其他使用者的訪問許可權 */
umask(S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
if(creat("bar", RWRWRW) < 0)
err_sys("create error for bar");
exit(0);
}
更改程序的檔案模式建立遮蔽字不影響父程序的遮蔽字
chmod函式例項
#include "apue.h"
int main(void)
{
struct stat statbuf;
/* turn on set-group-ID and turn off group-execute */
if(stat("foo", &statbuf) < 0)
err_sys("stat error for foo");
/*
int chmod(const char *pathname, mode_t mode);
更改檔案訪問許可權
程序的有效使用者ID必須等於檔案的所有者ID，或該程序必須具有超級使用者許可權
*/
if(chmod("foo", (statbuf.st_mode & ~S_IXGRP) | S_ISGID) < 0)
err_sys("chmod error for foo");
/* set absolute mode to "rw-r--r--" */
if(chmod("bar", S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) < 0)
err_sys("chmod error for bar");
exit(0);
}
組執行位為S，表示設定組ID位已設定，同時，組執行位則未設定
開啟一個檔案，然後unlink
#include "apue.h"
#include <fcntl.h>
int main(void)
{
if(open("tempfile", O_RDWR) < 0)
err_sys("open error");
/*
int unlink(const char *pathname);
刪除一個現有的目錄項
當開啟檔案程序數為0， 連結計數等於0時，才可被刪除
*/
if(unlink("temfile") < 0)
err_sys("unlink error");
printf("file unlinked\n");
sleep(2);
printf("down\n");
exit(0);
}
utime函式例項
目的：將檔案長度截段為0，但並不更改起訪問時間及修改時間
#include "apue.h"
#include <fcntl.h>
#include <utime.h>
int main(int argc, char *argv[])
{
int i, fd;
struct stat statbuf;
struct utimbuf timebuf;
for(i=1; i<argc; i++)
{
/* fetch current times */
if(stat(argv[i], &statbuf) < 0)
{
err_ret("%s: stat error", argv[i]);
continue;
}
/* truncate */
if((fd = open(argv[i], O_RDWR | O_TRUNC)) < 0)
{
err_ret("%s: open error", argv[i]);
continue;
}
close(fd);
timebuf.actime = statbuf.st_atime; /* access time */
timebuf.modtime = statbuf.st_mtime; /* modification time */
/*
int utime(const char *pathname, const struct utimbuf *times);
修改檔案的訪問和修改時間
struct utimebuf
{
time_t actime; access time
time_t modtime; modification time
}
*/
if(utime(argv[i], &timebuf) < 0)
{
err_ret("%s: utime error", argv[i]);
continue;
}
}
exit(0);
}yjp@yjp-VirtualBox:~/apue/4filedir$ ls -l changemode 檢視長度和最後修改時間
-rwxr-x--- 1 yjp yjp 13712 5月 16 21:18 changemode
yjp@yjp-VirtualBox:~/apue/4filedir$ ls -lu changemode 檢視最後訪問時間
-rwxr-x--- 1 yjp yjp 13712 5月 16 21:19 changemode
yjp@yjp-VirtualBox:~/apue/4filedir$ date 列印當天日期
2018年 05月 17日 星期四 13:45:18 CST
yjp@yjp-VirtualBox:~/apue/4filedir$ ./utime changemode 執行程式
yjp@yjp-VirtualBox:~/apue/4filedir$ ls -l changemode 檢查最後修改時間
-rwxr-x--- 1 yjp yjp 0 5月 16 21:18 changemode
yjp@yjp-VirtualBox:~/apue/4filedir$ ls -lu changemode 檢查最後訪問時間
-rwxr-x--- 1 yjp yjp 0 5月 16 21:19 changemode
yjp@yjp-VirtualBox:~/apue/4filedir$ ls -lc changemode 檢查更改狀態時間
-rwxr-x--- 1 yjp yjp 0 5月 17 13:45 changemode
遞迴降序遍歷目錄層次結構，並按檔案型別計數
#include "apue.h"
#include <dirent.h>
#include <limits.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;
if(argc != 2)
err_quit("usage: ftw <starting-pathname>");
ret = myftw(argv[1], myfunc);
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 = %7d, %5.2f %%\n", nreg, nreg*100.0/ntot);
printf("directories = %7d, %5.2f %%\n", ndir, ndir*100.0/ntot);
printf("block special = %7d, %5.2f %%\n", nblk, nblk*100.0/ntot);
printf("char special = %7d, %5.2f %%\n", nchr, nchr*100.0/ntot);
printf("FIFOs = %7d, %5.2f %%\n", nfifo, nfifo*100.0/ntot);
printf("symbolic links = %7d, %5.2f %%\n", nslink, nslink*100.0/ntot);
printf("socks = %7d, %5.2f %%\n", nsock, nsock*100.0/ntot);
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 int myftw(char *pathname, Myfunc *func)
{
int len = 4096;
/* malloc's for PATH_MAX+1 bytes
用來存放整個路徑，包括子資料夾
*/
fullpath = malloc(len);
strncpy(fullpath, pathname, len); /* protect against */
fullpath[len-1] = 0;
printf("len: %d\n", len);
printf("%s\n", pathname);
printf("%s\n", fullpath);
printf("%d\n", strlen(fullpath));
return(dopath(func));
}
/*
Descend through the hierarchy, starting at "fullpath".
If "fullpath" is anyting 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 dopath(Myfunc *func)
{
struct stat statbuf;
/*
struct dirent
{
ino_t d_ino; i-node number
char d_name[NAME_MAX+1] null-terminated filename
}
*/
struct dirent *dirp;
DIR *dp;
int ret;
char *ptr;
if(lstat(fullpath, &statbuf) < 0) /* stat error */
return (func(fullpath, &statbuf, FTW_NS));
if(!S_ISDIR(statbuf.st_mode)) /* 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;
/*
DIR *opendir(const char *pathname);
執行初始化操作，時第一個readdir讀目錄的第一個目錄項
*/
if((dp = opendir(fullpath)) == NULL) /* can't read directory */
return(func(fullpath, &statbuf, FTW_DNR));
/*
struct dirent *readdir(DIR *dp);
*/
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 */
printf("%s\n", fullpath);
if((ret = dopath(func)) != 0) /* recursive */
break; /* time to leave */
}
ptr[-1] = 0; /* erase everything from slash onwards */
/*
int closedir(DIR *dp);
*/
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_IFDIR: err_dump("for S_IFDIR for %s", pathname);
/* directories should have type = FTW_D */
default:
err_dump("wrong type %d for pathname %s", type, pathname);
break;
}
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("unkown type %d for pathname %s", type, pathname);
break;
}
return 0;
}
chdir函式例項
當前工作目錄是程序的一個屬性，所以隻影響呼叫chdir的程序本身，不影響其他程序，即呼叫該程式不會得到希望的結果
#include "apue.h"
int main(void)
{
/*
int chdir(const char *pathname);
更改工作目錄
*/
if(chdir("/tmp") < 0)
err_sys("chdir failed");
printf("chdir to /tmp successed\n");
exit(0);
}
getcwd函式例項
#include "apue.h"
int main(void)
{
char *ptr;
int size;
if(chdir("/tmp") < 0)
err_sys("chdir failed");
ptr = path_alloc(&size); /* our own function */
/*
char *getcwd(char *buf, size_t size);
得到當前工作目錄
從當前工作目錄.開始，用..目錄找上一級目錄，然後讀目錄項，
直到該目錄項中的i節點編號與工作目錄i節點編號相同，這就找到了對應的檔名
buf: 容納絕對路徑名+null終止字元
size: buf長度
*/
if(getcwd(ptr, size) == NULL)
err_sys("getcwd failed");
printf("cwd = %s\n", ptr);
exit(0);
}
列印st_dev和st_rdev值
#include "apue.h"
#ifdef SOLAPRIS
#include <sys/mkdev.h>
#endif
int main(int argc, char *argv[])
{
int i;
struct stat buf;
for(i=1; i<argc; i++)
{
printf("%s: ", argv[i]);
if(stat(argv[i], &buf) < 0)
{
err_ret("stat error");
continue;
}
/* 列印主裝置號和從裝置號 */
printf("dev = %d/%d", major(buf.st_dev), minor(buf.st_dev));
if(S_ISCHR(buf.st_mode) || S_ISBLK(buf.st_mode))
{
printf("(%s) rdev = %d/%d",
(S_ISCHR(buf.st_mode)) ? "character" : "block",
major(buf.st_rdev), minor(buf.st_rdev));
}
printf("\n");
}
exit(0);
}
第一個是目錄，後兩個是裝置
裝置號不同，說明位於不同的檔案系統
兩個終端裝置(st_dev）的檔名和i節點在裝置0/6上（devfs偽檔案系統），實際裝置號是4/0和4/1