linux编程fcntl获取和设置文件状态

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#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <fcntl.h>   #define ERR_EXIT( m ) \         do \         { \                 perror( m ); \                 exit( EXIT_FAILURE ); \         }while( 0 )   //设置某个文件状态 void set_flag( int fd, int flags ); //清除某个文件状态 void clear_flag( int fd, int flags );   int main( int argc, char* argv[] ) {           char buf[64] = { 0 };         int nread;           //设置非阻塞状态         set_flag( 0, O_NONBLOCK );         //清除非阻塞状态, 读取标准输入又变成阻塞         clear_flag( 0, O_NONBLOCK );         nread = read( 0, buf, 64 );         if( -1 == nread ) {                 ERR_EXIT( "获取输入失败" );         }         printf( "buf=%s\n", buf );           return 0; }   void set_flag( int fd, int flags ) {         int oldflag;         oldflag = fcntl( fd, F_GETFL, 0 );         if( -1 == oldflag ) {                 ERR_EXIT( "获取原来的状态失败" );         }           oldflag = oldflag | flags;         int ret = fcntl( fd, F_SETFL, oldflag );         if( -1 == ret ) {                 ERR_EXIT( "设置新的文件状态失败" );         } }   void clear_flag( int fd, int flags ) {         int oldflag;         oldflag = fcntl( fd, F_GETFL, 0 );         if( -1 == oldflag ) {                 ERR_EXIT( "获取原来的状态失败" );         }         oldflag = oldflag & ~flags;         int ret = fcntl( fd, F_SETFL, oldflag );         if( -1 == ret ) {                 ERR_EXIT( "设置新的文件状态失败" );         } }