linux编程stat检测文件元数据信息

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>

#define ERR_EXIT( m ) 
        do
        { 
                perror( m ); 
                exit( EXIT_FAILURE ); 
        }while( 0 )

#define MAJOR( a ) (int)((unsigned short)a >> 8 ) //获取高8位
#define MINOR( a ) (int)((unsigned short)a & 0xFF ) //获取低8位


//检测文件类型
int filetype( struct stat* st, char* filetype );

//检测文件权限
void fileperm( struct stat* st, char* perm );

int main( int argc, char* argv[] ) {

        int ret;
        if( argc != 2 ) {
                fprintf( stderr, "usage:%s filename
", argv[0] );
                exit( EXIT_FAILURE );
        }

        struct stat st;

        ret = stat( argv[1], &st );
        if( -1 == ret ) {
                ERR_EXIT( "stat file error" );
        }

        printf( "文件大小:st_size=%d
", st.st_size );
        printf( "用户id:uid=%d
", st.st_uid );
        printf( "组id:gid=%d
", st.st_gid );
        //printf( "主设备号:major_dev=%d
", MAJOR( st.st_dev ) );
        //printf( "次设备号:minor_dev=%d
", MINOR( st.st_dev ) );
        printf( "i节点:st_ino=%d
", st.st_ino );

        char filetypestr[64] = { 0 };
        int ftype = filetype( &st, filetypestr );
        if( ftype == 3 || ftype == 5 ) {
                printf( "文件类型:%s
", filetypestr );
                printf( "主设备号:%d, 次设备号:%d
", MAJOR( st.st_dev ), MINOR( st.st_dev ) );
        }else {
                printf( "文件类型:%s
", filetypestr );
        }

        char perm[11];
        fileperm( &st, perm );
        printf( "文件权限:%o, %s
", st.st_mode & 07777, perm );

        return 0;
}


//检测文件类型,设置文件返回1 其他文件返回0
/*
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
*/
int filetype( struct stat* st, char* filetype ) {

        mode_t mode = st->st_mode;
        int flag = 0;

        char* filetypes[] = {
                "socket",
                "symbolic link",
                "regular file",
                "block device",
                "directory",
                "character device",
                "fifo"
        };

        switch( mode & S_IFMT ){
                case S_IFSOCK:
                        strncpy( filetype, filetypes[0], strlen( filetypes[0] ) );
                        flag = 0;
                        break;
                case S_IFLNK:
                        strncpy( filetype, filetypes[1], strlen( filetypes[1] ) );
                        flag = 1;
                        break;
                case S_IFREG:
                        strncpy( filetype, filetypes[2], strlen( filetypes[2] ) );
                        flag = 2;
                        break;
                case S_IFBLK:
                        strncpy( filetype, filetypes[3], strlen( filetypes[3] ) );
                        flag = 3;
                        break;
                case S_IFDIR:
                        strncpy( filetype, filetypes[4], strlen( filetypes[4] ) );
                        flag = 4;
                        break;
                case S_IFCHR:
                        strncpy( filetype, filetypes[5], strlen( filetypes[5] ) );
                        flag = 5;
                        break;
                case S_IFIFO:
                        strncpy( filetype, filetypes[6], strlen( filetypes[6] ) );
                        flag = 6;
                        break;
        }

        return flag;
}


//检测文件权限
/*
 S_IRWXU    00700     mask for file owner permissions
 S_IRUSR    00400     owner has read permission
 S_IWUSR    00200     owner has write permission
 S_IXUSR    00100     owner has execute permission
 S_IRWXG    00070     mask for group permissions
 S_IRGRP    00040     group has read permission
 S_IWGRP    00020     group has write permission
 S_IXGRP    00010     group has execute permission
 S_IRWXO    00007     mask for permissions for others (not in group)
 S_IROTH    00004     others have read permission
 S_IWOTH    00002     others have write permission
 S_IXOTH    00001     others have execute permission
*/
void fileperm( struct stat* st, char* perm ) {

        strncpy( perm, "----------", 10 );
        perm[0] = '?';
        mode_t mode = st->st_mode;

        char typestr[64] = { 0 };
        char* abbreviation[] = {
                "s", //socket
                "l", //symbolic link
                "-", //regular file
                "b", //block file
                "d", //directory
                "c", //charactor device
                "p"  //fifo
        };

        int ret = filetype( st, typestr );
        strncpy( perm, abbreviation[ret], 1 );

        //检测文件所属的用户权限
        if( mode & S_IRUSR ){
                perm[1] = 'r';
        }
        if( mode & S_IWUSR ){
                perm[2] = 'w';
        }
        if( mode & S_IXUSR ){
                perm[3] = 'x';
        }

        //检测用户组权限
        if( mode & S_IRGRP ){
                perm[4] = 'r';
        }
        if( mode & S_IWGRP ){
                perm[5] = 'w';
        }
        if( mode & S_IXGRP ){
                perm[6] = 'x';
        }

        //检测其他组权限
        if( mode & S_IROTH ){
                perm[7] = 'r';
        }
        if( mode & S_IWOTH ){
                perm[8] = 'w';
        }
        if( mode & S_IXOTH ){
                perm[9] = 'x';
        }
        perm[10] = '';
}