王通seo/山东seo优化
//标准IO 操作中 ---系统调用的函数
fdopen() //将fd 转换 成 FILE *
fileno() //将FILE *转换 为 fd
FILE *fdopen(int fd,const char *mode);
功能:
将fd 转换 成 FILE *
参数:
@fd 要操作fd
@mode 打开的模式
返回值:
成功 FILE *
失败 NULL
int fileno(FILE *stream);
功能:
将FILE *转换 为 fd
参数:
@stream 要转换流指针
返回值:
成功 fd
失败 - && errno
fd = open(,O_RDONLY);
FILE *fp = fdopen(fd,"a");
#include<stdio.h>
#include<fcntl.h>int main(int argc, const char *argv[])
{int fd = open("1.txt",O_RDONLY);if(fd<0){perror("open fail");return -1;}printf("fd = %d\n",fd);FILE *fp = fdopen(fd,"r");if(fp == NULL){perror("fdopen fail");return -1;}printf("success\n");int fd1 = fileno(fp);printf("fileno = %d\n",fd1);return 0;
}
int feof(FILE *stream);
int ferror(FILE *stream);
使用的选择:
标准IO --- 可移植性 如果操作只是文本数据
文件IO --- 安全性 操作的是硬件 ---文件IO
操作目录:
目录也是一种文件
类似 标准IO
//1.打开
opendir
//2.读写
readdir
//3.关闭
closedir
DIR *opendir(const char *name);
功能:
打开目录，关联一个目录流
参数:
@name 要打开的目录名
返回值:
成功 返回DIR *
失败 NULL & errno
struct dirent *readdir(DIR *dirp);
功能:
读取目录项
参数:
@dirp 目录流指针
返回值:
成功 struct dirent *
失败 NULL && errno
struct dirent
{
ino_t d_ino; /* Inode number */
off_t d_off; /* Not an offset; see below */
unsigned short d_reclen;/* Length of this record */
unsigned char d_type;/* Type of file; not supported by all filesystem types */
char d_name[256]; /* Null-terminated filename */
}
注意:
读到文件末尾 NULL
int closedir(DIR *dirp);
功能:
关闭目录流
参数:
@dirp --- 目录流指针
返回值:
成功 0
失败 -1 &&errno
实现ls
#include<stdio.h>
#include<dirent.h>int main(int argc, const char *argv[])
{if(argc !=2){printf("Usage: %s<failname>",argv[0]);return -1;}DIR * dir = opendir(argv[1]);if(dir == NULL){perror("opendir fail");return -1;}printf("success\n");struct dirent *pdir = NULL;while(1){pdir = readdir(dir);if(pdir == NULL){break;}if(pdir->d_name[0]!='.'){printf("%s ",pdir->d_name);}}putchar('\n');closedir(dir);return 0;
}
实现shell
#include<stdio.h>
#include<dirent.h>int main(int argc, const char *argv[])
{if(argc !=2){printf("Usage: %s<failname>",argv[0]);return -1;}DIR * dir = opendir(argv[1]);if(dir == NULL){perror("opendir fail");return -1;}printf("success\n");struct dirent *pdir = NULL;int i = 0;int j = 0;while(1){pdir = readdir(dir);if(pdir == NULL){break;}if(pdir->d_type == DT_REG){i++;}else if(pdir->d_type == DT_DIR){j++;}}printf("regular=%d directory=%d",i,j);putchar('\n');closedir(dir);return 0;
}
chdir
chdir ("/home/linux"); "../../"
fopen("1.mp4")
int chdir(const char *path);// /home/linux
功能:
改变当前程序的工作路径
参数:
path:改变到的路径
返回值:
成功 返回0
失败 返回-1
/home/linux/Desktop/Music
"file.txt"
chdir("/root");
"file.txt"
getcwd //pwd
char *getcwd(char *buf, size_t size);
功能:
获得当前的工作路径
参数:
buf:保存工作路径空间的首地址
size:保存路径空间的长度
返回值:
成功返回包含路径空间的字符串首地址
失败返回NULL
#include<stdio.h>
#include<unistd.h>int main(int argc, const char *argv[])
{char buf[1024];getcwd(buf,sizeof(buf));printf("cwd = %s\n",buf);chdir("/home");getcwd(buf,sizeof(buf));printf("cwd = %s\n",buf);return 0;
}
mkdir
int a =200;
int mkdir(const char *pathname, mode_t mode);//777 666 --x--x--x
功能:
创建一个目录
666-
参数:
pathname:路径
mode:
mode & ~umask 0002
返回值:
成功 返回0
失败 返回-1
rmdir rm -fr rmdir
int rmdir(const char *pathname);
功能:
删除一个空目录文件
参数:
pathname:目录文件的名字
返回值:
成功 返回0
失败 返回-1
#include<stdio.h>
#include<sys/stat.h>
#include<sys/types.h>int main(int argc, const char *argv[])
{mkdir(argv[1],0777);// rmdir("ml");return 0;
}
stat
int stat(const char *pathname, struct stat *statbuf);
功能:
获得文件的状态信息
参数:
@pathname //需要一个文件名字
@statbuf //用来保存文件的属性信息
返回值:
成功 0
失败 -1
#include<stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>int main(int argc, const char *argv[])
{struct stat st;if(stat(argv[1],&st)<0){perror("stat fail");return -1;}printf("name = %s\n",argv[1]);printf("link = %ld\n",st.st_nlink);printf("size = %ld\n",st.st_size);printf("type = %o\n",st.st_mode & S_IFMT);printf("%d\n",(st.st_mode & S_IRUSR) == S_IRUSR);printf("%d\n",(st.st_mode & S_IWUSR) == S_IWUSR);printf("%d\n",(st.st_mode & S_IXUSR) == S_IXUSR);(st.st_mode & S_IRUSR) ? putchar('r'):putchar('-');(st.st_mode & S_IWUSR) ? putchar('w'):putchar('-');(st.st_mode & S_IXUSR) ? putchar('x'):putchar('-');putchar('\n');return 0;
}
附stst
struct stat {
dev_t st_dev; /* ID of device containing file */
ino_t st_ino; /* Inode number */
mode_t st_mode; /* File type and mode */ ? unsigned int
nlink_t st_nlink; /* Number of hard links */
uid_t st_uid; /* User ID of owner */
gid_t st_gid; /* Group ID of owner */
dev_t st_rdev; /* Device ID (if special file) */
off_t st_size; /* Total size, in bytes */
blksize_t st_blksize; /* Block size for filesystem I/O */
blkcnt_t st_blocks; /* Number of 512B blocks allocated */
struct timespec st_atim; /* Time of last access */
struct timespec st_mtim; /* Time of last modification */
struct timespec st_ctim; /* Time of last status change */
};
st_mode //unsigned int
4字节
32位
S_IFMT 0170000 bit mask for the file type bit field
S_IFSOCK 0140000 socket
S_IFLNK 0120000 symbolic link
S_IFREG 0100000 regular file
S_IFBLK 0060000 block device
S_IFDIR 0040000 directory
S_IFCHR 0020000 character device
S_IFIFO 0010000 FIFO
S_IRWXU 00700 owner has read, write, and execute permission
S_IRUSR 00400 owner has read permission
S_IWUSR 00200 owner has write permission
S_IXUSR 00100 owner has execute permission
S_IRWXG 00070 group has read, write, and execute permission
S_IRGRP 00040 group has read permission
S_IWGRP 00020 group has write permission
S_IXGRP 00010 group has execute permission
S_IRWXO 00007 others (not in group) have read, write, and
execute permission
S_IROTH 00004 others have read permission
S_IWOTH 00002 others have write permission
S_IXOTH 00001 others have execute permission
1 4 0000
st_mode 成员变量
...|17 16 15 |14 13 12 |11 10 9 |8 7 6 |5 4 3 |2 1 0
001 100 000 000 000 000
001 000 000 000 000 000
001 111 000 000 000 000
010 000 000
man stat //
man inode //详细说明
实现stat
File: ls.c
Size: 467 Blocks: 8 IO Block: 4096 regular file
Device: 803h/2051d Inode: 1318534 Links: 1
Access: (0664/-rw-rw-r--) Uid: ( 1000/ linux) Gid: ( 1000/ linux)
Access: 2025-02-17 11:25:46.611546129 +0800
Modify: 2025-02-17 11:25:46.595546514 +0800
Change: 2025-02-17 11:25:46.595546514 +0800
Birth: -
#include<stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <pwd.h>
#include<time.h>
#include <grp.h>
int main(int argc, const char *argv[])
{struct stat st;if(lstat(argv[1],&st)<0){perror("stat fail");return -1;}printf("name: %s\n",argv[1]);printf("size: %ld\t",st.st_size);printf("blocks: %ld\t",st.st_blocks);printf("blksize: %ld\t",st.st_blksize);char type = 0;switch(st.st_mode & S_IFMT){case S_IFSOCK:type = 's';printf("socket file\n");break;case S_IFLNK:type = 'l';printf("symlink file\n");break;case S_IFREG:type = '-';printf("regular file\n");break;case S_IFBLK:type = 'b';printf("blocks file\n");break;case S_IFDIR:type = 'd';printf("directory file\n");break;case S_IFCHR:type = 'c';printf("character file\n");break;case S_IFIFO:type = 'p';printf("pipe file\n");break;}printf("Device= %ld\t",st.st_dev);printf("Links = %ld\t",st.st_nlink);printf("Inode = %ld\n",st.st_ino);printf("Access:");printf("%#o/%c",st.st_mode&0777,type);(st.st_mode & S_IRUSR) ? putchar('r'):putchar('-');(st.st_mode & S_IWUSR) ? putchar('w'):putchar('-');(st.st_mode & S_IXUSR) ? putchar('x'):putchar('-');(st.st_mode & S_IRGRP) ? putchar('r'):putchar('-');(st.st_mode & S_IWGRP) ? putchar('w'):putchar('-');(st.st_mode & S_IXGRP) ? putchar('x'):putchar('-');(st.st_mode & S_IROTH) ? putchar('r'):putchar('-');(st.st_mode & S_IWOTH) ? putchar('w'):putchar('-');(st.st_mode & S_IXOTH) ? putchar('x'):putchar('-');putchar('\t');printf("Uid:(%d / %s)\t",st.st_uid,getpwuid(st.st_uid)->pw_name);printf("Gid:(%d / %s)\n",st.st_gid,getgrgid(st.st_gid)->gr_name);struct tm *p = NULL;p = localtime(&st.st_atime);p = localtime(&st.st_mtime);p = localtime(&st.st_ctime);printf("Access: %d-%d-%d %d:%d:%d \n",p->tm_year+1900,p->tm_mon+1,p->tm_mday,p->tm_hour,p->tm_min,p->tm_sec);printf("Modify: %d-%d-%d %d:%d:%d \n",p->tm_year+1900,p->tm_mon+1,p->tm_mday,p->tm_hour,p->tm_min,p->tm_sec);printf("Change: %d-%d-%d %d:%d:%d \n",p->tm_year+1900,p->tm_mon+1,p->tm_mday,p->tm_hour,p->tm_min,p->tm_sec);return 0;
}