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函数名: setvbuf
用 法: int setvbuf(FILE *stream, char *buf, int type, unsigned size);
type ： 期望缓冲区的类型：
_IOFBF(满缓冲）：当缓冲区为空时，从流读入数据。或者当缓冲区满时，向流写入数 据。
_IOLBF(行缓冲）：每次从流中读入一行数据或向流中写入一行数据。
_IONBF(无缓冲）：直接从流中读入数据或直接向流中写入数据，而没有缓冲区。
size ： 缓冲区内字节的数量。
注意：This function should be called once the file associated with the stream has already been opened but before any input or output operation has taken place.
意思是这个函数应该在打开流后,立即调用,在任何对该流做输入输出前
程序例
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#include <stdio.h>int main(){ FILE *input, *output; char bufr[512]; input = fopen("file.in", "r+b"); output = fopen("file.out", "w"); /* set up input stream for minimal disk access, using our own character buffer */ if (setvbuf(input, bufr, _IOFBF, 512) != 0) printf("failed to set up buffer for input file
"); else printf("buffer set up for input file
"); /* set up output stream for line buffering using space that will be obtained through an indirect call to malloc */ if (setvbuf(output, NULL, _IOLBF, 132) != 0) printf("failed to set up buffer for output file
"); else printf("buffer set up for output file
"); /* perform file I/O here */ /* close files */ fclose(input); fclose(output); return 0;} |