linux文件和目录的操作函数

//获取文件的属性

extern int stat (__const char *__restrict __file, struct stat *__restrict __buf) __THROW __nonnull ((1, 2));

extern int fstat (int __fd, struct stat *__buf) __THROW __nonnull ((2));

extern int lstat (__const char *__restrict __file, struct stat *__restrict __buf) __THROW __nonnull ((1, 2));

具体属性如下：

struct stat
  {
    __dev_t st_dev;            /* Device.  */    //设备号
    unsigned short int __pad1;
#ifndef __USE_FILE_OFFSET64
    __ino_t st_ino;            /* File serial number.    */   //文件的i-node节点号
#else
    __ino_t __st_ino;            /* 32bit file serial number.    */
#endif
    __mode_t st_mode;            /* File mode.  */     //文件的访问权限和文件类型等属性信息
    __nlink_t st_nlink;            /* Link count.  */       //文件的链接数
    __uid_t st_uid;            /* User ID of the file's owner.    */   //文件的用户id
    __gid_t st_gid;            /* Group ID of the file's group.*/    //文件的组id
    __dev_t st_rdev;            /* Device number, if device.  */
    unsigned short int __pad2;
#ifndef __USE_FILE_OFFSET64
    __off_t st_size;            /* Size of file, in bytes.  */   //文件大小
#else
    __off64_t st_size;            /* Size of file, in bytes.  */
#endif
    __blksize_t st_blksize;        /* Optimal block size for I/O.  */   //文件块大小

#ifndef __USE_FILE_OFFSET64
    __blkcnt_t st_blocks;        /* Number 512-byte blocks allocated. */  //文件所占块个数
#else
    __blkcnt64_t st_blocks;        /* Number 512-byte blocks allocated. */
#endif
#if defined __USE_MISC || defined __USE_XOPEN2K8
    /* Nanosecond resolution timestamps are stored in a format
       equivalent to 'struct timespec'.  This is the type used
       whenever possible but the Unix namespace rules do not allow the
       identifier 'timespec' to appear in the <sys/stat.h> header.
       Therefore we have to handle the use of this header in strictly
       standard-compliant sources special.  */
    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.  */
# define st_atime st_atim.tv_sec    /* Backward compatibility.  */
# define st_mtime st_mtim.tv_sec
# define st_ctime st_ctim.tv_sec
#else
    __time_t st_atime;            /* Time of last access.  */     
    unsigned long int st_atimensec;    /* Nscecs of last access.  */
    __time_t st_mtime;            /* Time of last modification.  */
    unsigned long int st_mtimensec;    /* Nsecs of last modification.  */
    __time_t st_ctime;            /* Time of last status change.  */
    unsigned long int st_ctimensec;    /* Nsecs of last status change.  */
#endif
#ifndef __USE_FILE_OFFSET64
    unsigned long int __unused4;
    unsigned long int __unused5;
#else
    __ino64_t st_ino;            /* File serial number.    */
#endif
  };

st_mode的文件类型宏：

#define    __S_ISTYPE(mode, mask)    (((mode) & __S_IFMT) == (mask))

#define    S_ISDIR(mode)     __S_ISTYPE((mode), __S_IFDIR)
#define    S_ISCHR(mode)     __S_ISTYPE((mode), __S_IFCHR)
#define    S_ISBLK(mode)     __S_ISTYPE((mode), __S_IFBLK)
#define    S_ISREG(mode)     __S_ISTYPE((mode), __S_IFREG)
#ifdef __S_IFIFO
# define S_ISFIFO(mode)     __S_ISTYPE((mode), __S_IFIFO)
#endif
#ifdef __S_IFLNK
# define S_ISLNK(mode)     __S_ISTYPE((mode), __S_IFLNK)
#endif

#if defined __USE_BSD && !defined __S_IFLNK
# define S_ISLNK(mode)  0
#endif

#if (defined __USE_BSD || defined __USE_UNIX98 || defined __USE_XOPEN2K) \
    && defined __S_IFSOCK
# define S_ISSOCK(mode) __S_ISTYPE((mode), __S_IFSOCK)
#elif defined __USE_XOPEN2K
# define S_ISSOCK(mode) 0
#endif

st_mode访问权限宏：

#define    S_ISUID __S_ISUID    /* Set user ID on execution.  */
#define    S_ISGID    __S_ISGID    /* Set group ID on execution.  */

#if defined __USE_BSD || defined __USE_MISC || defined __USE_XOPEN
/* Save swapped text after use (sticky bit).  This is pretty well obsolete.  */
# define S_ISVTX    __S_ISVTX
#endif

#define    S_IRUSR    __S_IREAD    /* Read by owner.  */
#define    S_IWUSR    __S_IWRITE    /* Write by owner.  */
#define    S_IXUSR    __S_IEXEC    /* Execute by owner.  */
/* Read, write, and execute by owner.  */
#define    S_IRWXU    (__S_IREAD|__S_IWRITE|__S_IEXEC)

#if defined __USE_MISC && defined __USE_BSD
# define S_IREAD    S_IRUSR
# define S_IWRITE    S_IWUSR
# define S_IEXEC    S_IXUSR
#endif

#define    S_IRGRP    (S_IRUSR >> 3)    /* Read by group.  */
#define    S_IWGRP    (S_IWUSR >> 3)    /* Write by group.  */
#define    S_IXGRP    (S_IXUSR >> 3)    /* Execute by group.  */
/* Read, write, and execute by group.  */
#define    S_IRWXG    (S_IRWXU >> 3)

#define    S_IROTH    (S_IRGRP >> 3)    /* Read by others.  */
#define    S_IWOTH    (S_IWGRP >> 3)    /* Write by others.  */
#define    S_IXOTH    (S_IXGRP >> 3)    /* Execute by others.  */
/* Read, write, and execute by others.  */
#define    S_IRWXO    (S_IRWXG >> 3)

//测试进程实际用户ID对文件的访问权限

/* Test for access to NAME using the real UID and real GID.  */
extern int access (__const char *__name, int __type) __THROW __nonnull ((1));

__type可取值：

/* Values for the second argument to access.
   These may be OR'd together.  */
#define    R_OK    4        /* Test for read permission.  */
#define    W_OK    2        /* Test for write permission.  */
#define    X_OK    1        /* Test for execute permission.  */
#define    F_OK    0        /* Test for existence.  */

//设置文件访问权限屏蔽位，哪个权限为（如S_IRUID)置位了，就无法设置这个权限

extern __mode_t umask (__mode_t __mask) __THROW;

//修改文件的st_mode,也就是修改文件的访问权限

extern int chmod (__const char *__file, __mode_t __mode) THROW __nonnull ((1));

extern int fchmod (int __fd, __mode_t __mode) __THROW;

extern int lchmod (__const char *__file, __mode_t __mode) THROW __nonnull ((1));

//修改文件的用户ID和组ID,不修改则赋值为-1

extern int chown (__const char *__file, __uid_t __owner, __gid_t __group) THROW __nonnull ((1)) __wur;

extern int fchown (int __fd, __uid_t __owner, __gid_t __group) __THROW __wur;

extern int lchown (__const char *__file, __uid_t __owner, __gid_t __group) THROW __nonnull ((1)) __wur;

//文件截断为参数length所示的长度

extern int truncate (__const char *__file, __off_t __length) __THROW __nonnull ((1)) __wur;

extern int ftruncate (int __fd, __off_t __length) __THROW __wur;

extern int remove (__const char *__filename) __THROW;

extern int rename (__const char *__old, __const char *__new) __THROW;

extern int mkdir (__const char *__path, __mode_t __mode) __THROW __nonnull ((1));

extern int rmdir (__const char *__path) __THROW __nonnull ((1));

#include    "unp.h"
#include "apue.h"
#include <stdio.h>
#include <sys/msg.h>
#include <sys/shm.h>
#include <sys/ipc.h>
#include <ctype.h>
//#include <linux/init.h>
//#include <linux/module.h>

int main(int argc, char *argv[])
{
    int rv;
    struct tm f_tm;
    struct stat f_stat;

    char curr_dir[100];

    if((rv = stat("/home/yang/exam_file/exam_file_op.dat", &f_stat)) < 0) {
        puts("get file stat info error");
    }

    if(S_ISREG(f_stat.st_mode)) {
        puts("this file is a regular file");
    }

    if(S_ISDIR(f_stat.st_mode)) {
        puts("this file is a directory file");
    }

    if(__S_ISTYPE(f_stat.st_mode, S_ISUID)) {
        puts("this file is set uid");
    }
    else {
        puts("this file is not set uid");
    }

    if(__S_ISTYPE(f_stat.st_mode, S_ISGID)) {
        puts("this file is set gid");
    }
    else {
        puts("this file is not set gid");
    }

    if( chmod("/home/yang/exam_file/exam_file_op.dat", f_stat.st_mode | S_ISUID) < 0) {
        puts("change mode error");
    }
    else {
        puts("change mode ok");
    }


    if(localtime_r(&f_stat.st_atim, &f_tm) == NULL) {
        puts("time format translationg failed");
    }
    printf("time: %d\n", f_tm.tm_year);

    printf("file size: %d\n", (int)f_stat.st_size);
    printf("file blk size: %d\n", (int)f_stat.st_blksize);
    printf("file blk cnt: %d\n", (int)f_stat.st_blocks);

    if(getcwd(curr_dir, sizeof(curr_dir)) == NULL ) {
        puts("get cwd error");
    }
    else {
        puts(curr_dir);
    }

    strcat(curr_dir, "/newdir");
    puts(curr_dir);

    if(rmdir("curr_dir") < 0) {
        err_sys("mkdir error");
    }


    if(mkdir("/home/yang/exam_file/newdir",S_IRWXU | S_IRWXG) < 0) {
        err_sys("mkdir error");
    }

    if(rename("/home/yang/exam_file/exam_file_op.dat", "/home/yang/exam_file/exam_file_op2.dat") < 0) {
        err_sys("rename error");
    }

    exit(0);
}