- //捕获fopen调用中的错误
- #include <stdio.h>
- #include <errno.h>
- #include <string.h>
- #define MYFILE "missing.txt"
- int main( )
- {
- FILE* fin;
- fin=fopen( MYFILE,"r" );
- if( fin==(FILE*)NULL )
- {
- printf( "%s: %s\n",MYFILE,strerror( errno ) );
- exit( -1 );
- }
- fclose( fin );
- return 0;
- }
- /*数据的读写
- 标准的I/O库提供了缓冲接口。有两个非常重要的属性:
- 1、系统是分块进行读写的(一个块通常8KB)。字符I/O都写到FILE缓冲区中,
- 这个缓冲区满的时候会自动写入介质;
- 2、如果数据需要送到像控制台终端这样的交互设备,必须设置fflush或者非缓冲
- I/O
- */
- /********字符接口**********/
- //fputc字符接口实例
- #include <stdio.h>
- #include <errno.h>
- int main( )
- {
- int i=0;
- FILE* fout;
- const char string[ ]={
- "This\r\nis a test\r\nfile.\r\n\0"
- };
- fout=fopen("inpfile.txt","w");
- if( fout==( FILE* )NULL )
- {
- printf( "%s: %s\n","inpfile.txt",strerror( errno ) );
- exit( -1 );
- }
- while( string[ i ]!=NULL )
- {
- fputc( ( int )string[ i ],fout );
- ++i;
- }
- fclose( fout );
- return 0;
- }
- //fgetc字符接口实例
- #include <stdio.h>
- #include <errno.h>
- int main( )
- {
- FILE* fin;
- fin=fopen( "inpfile.txt","r" );
- if( fin==( FILE* )NULL )
- {
- printf( "%s: %s\n","inpfile.txt",strerror( errno ) );
- exit( -1 );
- }
- int i;
- while( (i=fgetc( fin ))&&i!=EOF )
- {
- printf( "%c",(char)i );
- }
- return 0;
- }
- /*
- fputc( )是向文件中写入数据;fgetc是从文件中读取数据
- 总结:字符接口使用简单,但是效率不高,最好是在基于字符串的方法不可使用时才使用字符接口
- */
- /************字符串接口************/
- /*提供字符串读写函数4个。fputs和fgets是简单的字符串接口;
- fprintf和fscanf更复杂的接口,但提供了更多的功能。
- */
- //相文件中写入变长字符串
- #include <stdio.h>
- #include <errno.h>
- #include <stdlib.h>
- #define LEN 80
- int main( )
- {
- char line[ LEN+1 ];
- FILE* fout;
- FILE* fin;
- //写入数据
- fout=fopen( "testfile.txt","w" );
- if( fout==( FILE* )NULL )
- {
- printf( "%s: %s\n","testfile.txt",strerror( errno ) );
- exit( -1 );
- }
- fin=fdopen( 0,"r" ); //将fin与标准输入流绑定
- printf( "Please input some characters,end with CTRL+D:\n" );
- //CTRL+D结束输入
- while( ( fgets(line,LEN,fin) )!=NULL )
- {
- fputs( line,fout );
- }
- fclose( fout );
- fclose( fin );
- //读取数据
- printf( "\nthe characters read from file is:\n" );
- char getLine[ LEN+1 ];
- fin=fopen( "testfile.txt","r" );
- if( fin==(FILE*)NULL )
- {
- printf( "%s: %s\n","testfile.txt",strerror( errno ) );
- exit( -1 );
- }
- fgets( getLine,LEN,fin );
- printf( "%s\n",getLine );
- fclose( fin );
- return 0;
- }
- /*fputs向文件中写入,fgets从文件中读取
- 总结:要注意不可以同时读写同一个文件。
- */
- //以ASCII格式输出结构体数据
- #include <stdio.h>
- #include <errno.h>
- #define MAX_LINE 40
- #define FILENAME "myfile.txt"
- typedef struct
- {
- int id;
- float x_coord;
- float y_coord;
- char name[ MAX_LINE+1 ];
- }MY_TYPE_T;
- #define MAX_OBJECTS 3
- /*Initialize an array of three objects*/
- MY_TYPE_T objects[ MAX_OBJECTS ]={
- {0,1.5,8.3,"Frist-object"},
- {1,4.5,6.3,"Second-object"},
- {2,3.5,7.5,"Thrid-object"},
- };
- int main( )
- {
- int i;
- FILE* fout;
- fout=fopen(FILENAME,"w" );
- if( fout==( FILE* )NULL )
- {
- printf( "%s: %s\n",FILENAME,strerror( errno ) );
- exit( -1 );
- }
- printf( "Writing...\n" );
- for( i=0;i<MAX_OBJECTS;++i )
- {
- fprintf( fout,"%d %f %f %s\n",objects[ i ].id,objects[ i ].x_coord,
- objects[ i ].y_coord,objects[ i ].name);
- }
- fclose( fout );
- printf("Write over\n");
- printf("Read from file\n");
- FILE* fin=fopen( FILENAME,"r" );
- if( fin==(FILE*)NULL )
- {
- printf( "%s: %s\n",FILENAME,strerror( errno ) );
- exit( -1 );
- }
- MY_TYPE_T objects;
- while( !feof(fin) )
- {
- fscanf( fin,"%d %f %f %s\n",&objects.id,&objects.x_coord,
- &objects.y_coord,&objects.name);
- printf("%d %f %f %s\n",objects.id,objects.x_coord,
- objects.y_coord,objects.name);
- }
- fclose( fin );
- return 0;
- }
- /**************二进制文件的读写*****************/
- /*使用fwirte、fread进行二进制文件的读写
- 读写二进制文件的时候,要注意的重要问题是可移植性和字序问题。
- Intel采用小字节序,PowerPC和网络采用大字节序
- */
- #include <stdio.h>
- #include <errno.h>
- #define MAX_LINE 40
- #define FILENAME "myfile.bin"
- typedef struct
- {
- int id;
- float x_coord;
- float y_coord;
- char name[ MAX_LINE+1 ];
- }MY_TYPE_T;
- #define MAX_OBJECTS 3
- /*Initialize an array of three objects*/
- MY_TYPE_T objects[ MAX_OBJECTS ]={
- {0,1.5,8.3,"Frist-object"},
- {1,4.5,6.3,"Second-object"},
- {2,3.5,7.5,"Thrid-object"},
- };
- int main( )
- {
- int i;
- FILE* fout;
- fout=fopen(FILENAME,"w" );
- if( fout==( FILE* )NULL )
- {
- printf( "%s: %s\n",FILENAME,strerror( errno ) );
- exit( -1 );
- }
- printf( "Writing...\n" );
- fwrite( ( void* )objects,sizeof( MY_TYPE_T ),3,fout );
- fclose( fout );
- //使用fread/fseek/rewind读取二进制结构体数据
- printf( "Read from file\n" );
- MY_TYPE_T object;
- FILE* fin=fopen( FILENAME,"r" );
- if( fin==( FILE* )NULL )
- {
- printf( "%s: %s\n",FILENAME,strerror( errno ) );
- exit( -1 );
- }
- //定位到第三个结构体
- fseek( fin,( 2*sizeof( MY_TYPE_T ) ),SEEK_SET );
- fread( &object,sizeof( MY_TYPE_T ),1,fin );
- printf("%d %f %f %s\n",object.id,object.x_coord,
- object.y_coord,object.name);
- fseek( fin,( 1*sizeof( MY_TYPE_T ) ),SEEK_SET );
- fread( &object,sizeof( MY_TYPE_T ),1,fin );
- printf("%d %f %f %s\n",object.id,object.x_coord,
- object.y_coord,object.name);
- //把文件指针复位到文件开头
- rewind( fin );
- fread( &object,sizeof( MY_TYPE_T ),1,fin );
- printf("%d %f %f %s\n",object.id,object.x_coord,
- object.y_coord,object.name);
- fclose( fin );
- return 0;
- }
- /************************************************/
- /*
- 总结:上面所有的函数都是有一些基本API来实现的。比如:open/read/write/fdopen/pread/pwrite.
- 文件的输入输出API函数也可以用于管道和套接字。另外,文件和字符串操作是面向对象脚本语言的强项,如Ruby,Python.
- */
Linux文件编程实例
时间: 2024-10-17 00:40:33