ANSI C File 操作
File 操作参考网址 ： https://zh.cppreference.com/w/c/io
| API接口 | 说明 |
|---|---|
| fopen | int fopen(const char* filename,const char *mode) |
| fclose | int fclose(FILE * stream) |
| ftell | ftell(FILE* stream) 获取文件位置的指针 |
| feof | feof(FILE*stream) 如果到了文件末尾 返回 非0的值 否则返回0 |
| rewind | void rewind(FILE *stream) 将文件指针移动到文件的开头位置 |
| remove | remove(const char *filename) |
| rename | rename(const char*oldname,const char *newname) |
| fflush | int fflush(FILE*stream); 刷新文件缓冲区 |
| fgets | char* fgets(char str,int num , FILEstream) 从文件中读取一行 |
| fputs | int fputs(const char *str,FILE *stream); 输出一行字符串到文件中 |
| fread | int fread(void*buffer,int size,int count,FILE *stream) |
| fwrite | int fwrite(void *buffer,int size,int count,FILE *stream) |
| fseek | int fseek(FILE*stream,long int offset,int origin) |
| fprintf | int fprintf(FILE*stream,const char *format[,argument]) |
| fputc/fgetc | 从文件中读取/输出一个字符 |
fopen 函数原型
int fopen(const char* filename,const char *mode)
mode 可选项如下：
| mode | 说明 |
|---|---|
| r | 以只读方式打开文件，该文件必须存在 |
| w | 打开只写文件，如果文件不存在，则会创建一个新文件；程序会从文件的开头写入内容，如果文件存在，则该会被截断为零长度，重新写入 |
| a | 以追加模式写入文件，如果文件不存在，则会创建一个新文件，如果文件存在，程序会在已有的文件内容中追加内容 |
| r+ | 打开一个文本文件，允许读写文件，该文件必须存在 |
| w+ | 打开一个文本文件，允许读写文件；如果文件已存在，则文件会被截断为零长度，如果文件不存在，则会创建一个新文件 |
| a+ | 打开一个文本文件，允许读写文件；如果文件不存在，则会创建一个新文件；读取会从文件的开头开始，写入则只能是追加模式 |
如果打开的二进制文件，需要使用下面的访问模式：
rb", "wb", "ab", "rb+", "r+b", "wb+", "w+b", "ab+", "a+b"
预定义标准流：
stdin：和标准输入流关联的 File* 类型
stdout：和标准输出流关联的 File* 类型
stderr：和标准错误输出流关联的 File* 类型
int main(int argc,char * argv[])
{
MI_PRINT("This is my standard C demo! %s build date:%s %s\n",__FUNCTION__,__DATE__,__TIME__);
MI_PRINT("argv[1] is %s \n", argv[1]); // argv[0] is programme name
FILE *fp = fopen(argv[1],"w+");
CHECK_RET(fp);
MI_S32 count = 0;
while( !feof(fp))
{
count = fread(read_buffer,sizeof(MI_U8),buffer_size,fp);
// ftell(FILE* stream) 获取文件位置的指针
DBG_ERR("the read buffer length is %d content is %s \n",count,read_buffer);
MI_PRINT("The Current file location is %d \n",ftell(fp));
}
rewind(fp);
MI_PRINT("The Current file location is %d \n",ftell(fp));
strcpy(write_buffer,"this is tonychen add hahaha !!\n");
count = fwrite(write_buffer,sizeof(MI_U8),strlen(write_buffer),fp);
MI_PRINT("The write count is %d \n",count);
fflush(fp);
//MI_PRINT("The Current file location is %d \n",ftell(fp));
rewind(fp);
fgets(read_buffer,20,fp);
MI_PRINT("The readbuffer is %s \n",read_buffer);
fgets(read_buffer,100,fp);
MI_PRINT("The readbuffer is %s \n",read_buffer);
MI_S8 ret = -1;
if( (ret = remove("my.txt")) == 0) {
MI_PRINT("remove file success !! \n");
} else {
MI_PRINT("remove file fail \n");
}
ret = rename("my1.txt","my2.txt");
MI_PRINT("The ret value of my.txt is %d \n",ret);
rewind(fp);
fgets(read_buffer,100,stdin);
MI_PRINT("The readbuffer is %s \n",read_buffer);
fseek(fp,0,SEEK_SET);
fputs(read_buffer,fp);
fseek(fp,0,SEEK_SET);
MI_PRINT("The Current file location is %d \n",ftell(fp));
fseek(fp,0,SEEK_END);
MI_PRINT("The Current file location is %d \n",ftell(fp));
fseek(fp,-20,SEEK_END);
MI_PRINT("The Current file location is %d \n",ftell(fp));
rewind(fp);
fseek(fp,100,SEEK_CUR);
MI_PRINT("The Current file location is %d \n",ftell(fp));
fseek(fp,0,SEEK_END);
fprintf(fp,"This is MY demo %s %s \n",__DATE__,__TIME__);
fclose(fp);
return 0;
}
基本输入输出函数
| 元素 | 说明 |
|---|---|
| printf | 向终端输出格式化字符串 |
| puts/gets | puts(const char* buffer) |
| getc getchar | getc(char c，File* stream) |
| scanf | 从终端按照格式获取内容 |
| sscanf | 从Buffer 中按照格式获取内容 |
| sprintf | 按照格式化字符串组成buffer |
- sscanf 用法详解
sscanf int sscanf(char *buffer,const char *format[argument])
format:
%s 字符串 读取字符串截止的标志是 空格 跳格 或者 换行
%*s 忽略某个字符串
%[^/] 匹配字符 /
%[^=] 匹配字符 =
%*[^/] 忽略开始到 / 中间的字符串
%4s 截取前面四个字符串
void testsscanfOperation() {
printf(" %s start...... \n", __FUNCTION__);
uint8_t ValueA = 0;
uint8_t ValueB = 0;
uint8_t StringBufferP[100] = { 0 };
uint8_t StringBufferV[100] = { 0 };
uint8_t InputBuffer[100] = { 0 };
#if 0
/* %*s 表示忽略 某个字符串 */
/*读取字符串截止的标志是 空格 跳格 或者 换行*/
strcpy(InputBuffer, "3+5=4");
//strcpy(InputBuffer, "tony like reading");
sscanf(InputBuffer, "%d %s %d", &ValueA, StringBufferP, &ValueB);
printf("The ValueA is %d ValueB is %d \n", ValueA, ValueB);
#endif
strcpy(InputBuffer, "tony like reading");
sscanf(InputBuffer, "%s %*s %s", StringBufferP, &StringBufferV);
printf("The stringbufferP is %s \n", StringBufferP);
printf("The stringbufferV is %s \n", StringBufferV);
/*用于字符串的截取 特定的长度*/
strcpy(InputBuffer, "GodBlessyou");
sscanf(InputBuffer, "%3s", StringBufferP);
sscanf(InputBuffer, "%8s", StringBufferV);
printf("The stringbufferP is %s \n", StringBufferP);
printf("The stringbufferV is %s \n", StringBufferV);
strcpy(InputBuffer, "bootvideo=/system/media/bootvideo.mp4");
sscanf(InputBuffer, "%[^=] %*1s %s", StringBufferP, StringBufferV); // 忽略掉 = 字符
printf("The stringbufferP is %s \n", StringBufferP);
printf("The stringbufferV is %s \n", StringBufferV);
strcpy(InputBuffer, "/system/media/bootvideo.mp4");
sscanf(InputBuffer, "%*[^/] %s %*[^/]", StringBufferP);
printf("The stringbufferP is %s \n", StringBufferP);
// 截取 空格之前的字符串
sscanf("123456 abcdedf", "%[^ ]", StringBufferP);
printf("%s\n", StringBufferP);
// 表示只是匹配 1-9a-z 的字符串
sscanf("123456abcdedfBCDEF", "%[1-9a-z]", StringBufferP);
printf("%s\n", StringBufferP);
printf("--------------------- \n");
memset(InputBuffer, 0x00, sizeof(InputBuffer));
ValueA = 100;
ValueB = 200;
sprintf(InputBuffer, "%d is %s %d %s %d", ValueA + ValueB, "equal", ValueA, "+", ValueB);
printf("The InputBuffer is %s \n", InputBuffer);
}
运行结果：
demoMain Run ....
testsscanfOperation start......
The stringbufferP is tony
The stringbufferV is reading
The stringbufferP is God
The stringbufferV is GodBless
The stringbufferP is bootvideo
The stringbufferV is /system/media/bootvideo.mp4
The stringbufferP is bootvideo
123456
123456abcdedf
---------------------
The InputBuffer is 300 is equal 100 + 200
