C library functions - setvbuf ()
C standard library - <stdio.h>
description
C library functionsint setvbuf (FILE * stream, char * buffer, int mode, size_t size) to define how the flow stream buffer.
statement
Here is () statement setvbuf function.
int setvbuf(FILE *stream, char *buffer, int mode, size_t size)
parameter
- stream - This is a pointer to FILE pointer to an object, the object identifier FILE an open stream.
- buffer - which is assigned to the user buffer.If set to NULL, the function will automatically assign a specified buffer size.
- mode - This specifies the file buffer mode:
| 模式 | 描述 |
|---|---|
| _IOFBF | 全缓冲：对于输出，数据在缓冲填满时被一次性写入。对于输入，缓冲会在请求输入且缓冲为空时被填充。 |
| _IOLBF | 行缓冲：对于输出，数据在遇到换行符或者在缓冲填满时被写入，具体视情况而定。对于输入，缓冲会在请求输入且缓冲为空时被填充，直到遇到下一个换行符。 |
| _IONBF | 无缓冲：不使用缓冲。每个 I/O 操作都被即时写入。buffer 和 size 参数被忽略。 |
- size - this is the buffer size in bytes.
return value
If successful, the function returns 0, otherwise it returns a nonzero value.
Examples
The following example demonstrates setvbuf () function is used.
#include <stdio.h>
int main()
{
char buff[1024];
memset( buff, '\0', sizeof( buff ));
fprintf(stdout, "启用全缓冲\n");
setvbuf(stdout, buff, _IOFBF, 1024);
fprintf(stdout, "这里是 w3cschool.cc\n");
fprintf(stdout, "该输出将保存到 buff\n");
fflush( stdout );
fprintf(stdout, "这将在编程时出现\n");
fprintf(stdout, "最后休眠五秒钟\n");
sleep(5);
return(0);
}
Let's compile and run the above program, which will produce the following results. Here, a program to save the output buffer tobuff, until the first call to fflush ()before starting a buffered output of the last 5 seconds of sleep. It will be before the end of the program, to send the remaining output to STDOUT.
启用全缓冲 这里是 w3cschool.cc 该输出将保存到 buff 这将在编程时出现 最后休眠五秒钟