ch03: 檔案管理

 

第三講 檔案管理檔案模式       常規檔案管道（IPC）：Linux系統的處理序間通訊的一種機制，FIFO的檔案，有兩種管道：無名管道和具名管道目錄檔案：以檔案的方式進行操作裝置檔案：大多數物理裝置都用檔案來表示，有兩種裝置檔案：塊裝置和字元裝置符號串連：包含到定義檔案的特殊路徑，類似於windows下的捷徑通訊端：處理序間通訊的機制基本的檔案操作       inode（資訊節點）              核心資訊節點（in-core inode）：不同類型的檔案的核心資訊節點都是相同的              磁碟資訊節點（on-disk inode）：不同檔案系統類型具有不同的磁碟資訊節點       當一個進程開啟磁碟中的檔案，磁碟資訊節點就轉換成核心資訊節點，如果核心資訊節點被修改，則該節點的資訊將被傳回磁碟資訊節點1.       檔案模式檔案模式定義低12位：表示存取權限，用於管理對檔案的訪問和檔案許可權的修飾符寫成6個8進位數例：        041777        100755檔案存取權限        3個存取控制位        chmod        例-rwx------    1 root     root          218 5月 22 20:49 forkd.c [root@localhost ch02]# chmod 777 forkd.c -rwxrwxrwx    1 root     root          218 5月 22 20:49 forkd.c                     檔案許可權修飾符與類型                     是一個位元遮罩，表示setuid、setgid、stiky                     檔案類型                     sys/stat.h              進程的umask              #include<sys/stat.h>              int umask(int newmask);              例 [root@localhost tmp]# touch ex1[root@localhost tmp]# ls –l-rw-rw-r--    1 root     root            0 5月 22 21:56 ex1 [root@localhost tmp]#umask 077[root@localhost tmp]# touch ex2-rw-rw-r--    1 root     root            0 5月 22 21:56 ex1-rw-------    1 root     root            0 5月 22 21:58 ex2       2.基本的檔案操作              檔案描述符              stdin、stdout、stderr              #include <unistd.h>              STDIN_FILENO, STDOUT_FILENO,STDERR_FILENO              操作檔案的參數              關閉檔案              int close(int fd);              開啟檔案：              #include <fcntl.h>              int open(char *pathname, int flags, mode_t mode);              int create(char *pathname, mode_t mode);              flags: O_RDONLY, O_RDWR, O_WRONLY, O_CREATE, O_EXCL ,O_NOCTTY, O_TRUNC, O_APPEND, O_NONBLOCK, O_SYNC              open(pathname, O_CREAT|O_WRONLY|O_TRUNC, mode)              檔案的讀寫與位置指標的移動              #include <unistd.h>              size_t read(int fd, void *buf, size_t length);              size_t write(int fd, const void *buf, size_t length);              例// 寫檔案#include <errno.h>#include <fcntl.h>#include <stdio.h>#include <stdlib.h>#include <unistd.h>int main(void){       int fd;       if ((fd=open("rwexm",O_TRUNC|O_CREAT|O_WRONLY,0644))<0)       {              perror("open");              _exit(1);       }       if (write(fd,"hello world/n",13) != 13)       {              perror("write");              _exit(1);       }       close(fd);       return 0;} // 讀檔案#include <errno.h>#include <fcntl.h>#include <stdio.h>#include <stdlib.h>#include <unistd.h> int main(void){       int size = 13;       char buffer[size];       int fd;       if ((fd = open("rwexm",O_RDONLY,0644)) < 0)       {              perror("open");              _exit(1);       }       if (read(fd,buffer,sizeof(buffer)) < 0){              perror("read");              _exit(1);       }       printf(buffer);       close(fd);       return 0;}               int lseek(int fd, off_t offset, int whence);              SEEK_SET, SEEK_CUR, SEEK_END              局部讀寫              例              類比實現cat系統命令              #include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <errno.h>#include <fcntl.h> int main(int argc, char **argv){       int fd, len;       char buf[1024];              if ( argc < 2)       {              printf("at least 1 para/n");              return 0;       }              if ((fd = open(argv[1],O_RDONLY,0666)) < 0)       {              perror("open");              _exit(1);       }              while ((len = read(fd,buf,sizeof(buf))) > 0)       {              if (write(1,buf,len) != len)              {                     perror("write");                     close(fd);                     _exit(1);              }       }              if (len < 0)        {              perror("read");              close(fd);              _exit(1);       }              close(fd);                     return 0;}                            // 縮短檔案              int truncate(const char *pathname, size_t length);              int ftruncate(int fd, size_t length);                            // 同步：執行該函數後立刻將資料寫回到硬體              int fsync(int fd)              int fdatasync(int fd)查詢和修改inode資訊       查詢inode資訊       #include <sys/stat.h>       int stat(const char *pathname, struct stat *statbuf);       int lstat(const char *pathname, struct stat *statbuf);       int fstat(int fd, struct stat *statbuf);       struct stat成員       dev_t                 st_dev            unsigned long              st_block       ino_t            st_ino             time_t                    st_atime       mode_t          st_mode           time_t                    st_mtime       nlink_t          st_nlink            time_t                    st_ctime       uid_t            st_uid             unsigned long              st_blksize       gid_t            st_gid       dev_t            st_rdev       off_t             st_size       例#include <errno.h>#include <stdio.h>#include <string.h>#include <sys/stat.h>#include <sys/sysmacros.h>#include <time.h>#include <unistd.h> #define TIME_STRING_BUF 50 char *timeString(time_t t, char*buf){       struct tm *local;       local = localtime(&t);       strftime(buf, TIME_STRING_BUF,"%c",local);       return buf;      } int statFile(const char *file){       struct stat statbuf;       char timeBuf[TIME_STRING_BUF];              if (lstat(file,&statbuf))       {              fprintf(stderr,"could not lstat %s:%s/n",file,strerror(errno));              return 1;       }                   printf("filename: %s/n",file);       printf("on device: major %d/minor %d inod number: %ld/n",major(statbuf.st_dev),minor(statbuf.st_dev),statbuf.st_ino);       printf("size      :%x-10ld type:%07o      permissions       %05o/n",statbuf.st_size,statbuf.st_mode&S_IFMT,statbuf.st_mode&~(S_IFMT));       printf("owner:%d group:%d number of links:%d/n",statbuf.st_uid,statbuf.st_gid,statbuf.st_nlink);       printf("chnge time:%s/n",timeString(statbuf.st_ctime,timeBuf));       printf("modified time:%s/n",timeString(statbuf.st_mtime,timeBuf));       printf("access time:%s/n",timeString(statbuf.st_atime,timeBuf));        return 0;} int main(int argc, const char **argv){       int i;       int rc = 0;       for (i = 1; i < argc; i++)       {              rc |= statFile(argv[i]);              if ((argc -i) > 1)              {                     printf("/n");              }       }                          return rc;}#include <unistd.h>int access(const char *pathname, int mode);正確返回0，出錯返回EACCESS #include <sys/stat.h>int chmod(const char *pathname, mode_t mode);int fchmod(int fd, mode _t mode);返回EPERM #include <unistd.h>int chown(const char *pathname, uid_t owner, gid_t group);int fchown(int fd, uid_t owner, gid_t group); #include <utime.h>int utime(const char *pathname, strcut utimbuf *buf);#include<sys/time.h>int utimes(const char *pathname, struct timeval *tvp);struct utimbuf{       time_t actime;       time_t modtime;}struct timeval{       long tv_sec;       long tv_usec;} ext3擴充屬性EXT3_APPEND_FLEXT3_IMMUTABLE_FLEXT3_NODUMP_FLEXT3_SYNC_FL#include <sys/ioctl.h>#include <linux/ext3_fs.h>int ioctl(int fd, int request, void *arg);EXT3_IOC_GETFLAGS, EXT3_IOC_SETFLAGS例： 操作目錄項#include <fcntl.h>#include <unistd.h>int mknod(const char *pathname, mode_t mode, dev_t dev);S_IFIFO, S_IFBLK, S_IFCHR<sys/sysmacros.h> makedev(major, minor), major(), minor()/*建立永久連結*/#include <unistd.h>int link(const char  *origpath, const char *newpath); /*建立符號串連*/#include <unistd.h>int sysmlink(const char *origpath, const char *newpath);int readlink(const char *pathname, char *buf, size_t bufsize);chown(), lstat(), readlink(), rename(), unlink() /*刪除檔案*/#include <unistd.h>int unlink(char *pathname);int rename(const char *oldpath, const char *newpath);操作檔案描述符和建立無名管道#include <fcntl.h>Int fcntl(int fd, int command, long arg);fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_RDONLY);fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_APPEND);fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) & ~O_APPEND); /*複製檔案描述符*/int dup(int oldfd);int dup2(int oldfd, int newfd);int pipe(int fds[2]); 例#include <errno.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/stat.h>#include <sys/sysmacros.h>#include <unistd.h>#include <fcntl.h> void usage(void){       fprintf(stderr, "usage:mkmmodexa <path> [b|c|n|p] <major> <minor> /n");       _exit(1);} int main(int argc, char **argv){       int major = 0, minor = 0;       const char *path;       int mode = 0666;       char *end;       int args;              if (argc < 3 )       {              usage();       }              path = argv[1];        if (!strcmp(argv[2],"b"))       {              mode |= S_IFBLK;              args = 5;       }       else if (!strcmp(argv[2],"c") || !strcmp(argv[2],"m"))       {              mode |= S_IFCHR;              args = 5;       }       else if (!strcmp(argv[2],"p"))       {              mode |= S_IFIFO;              args = 3;       }       else       {              sprintf(stderr, "unknown node type %s/n",argv[2]);              return 1;       }        if (args == 5)       {              major = strtol(argv[3],&end,0);              if (*end)              {                     fprintf(stderr,"bad major number %s/n",argv[3]);                     return 1;              }              minor = strtol(argv[4],&end,0);              if (*end)              {                     fprintf(stderr, "bad major number %s/n",argv[4]);                     return 1;              }       }              if (mknod(path, mode, makedev(major, minor)))       {              fprintf(stderr, "mkmod failed:%s/n",strerror(errno));              return 1;       }       return 0;}