C参考手册
文件输入/输出 | File input/output
fgetpos
在头文件<stdio.h>中定义 |
|
|
---|---|---|
int fgetpos(FILE * stream,fpos_t * pos); |
|
(直到C99) |
int fgetpos(FILE * restrict stream,fpos_t * restrict pos); |
|
(自C99以来) |
获取文件流的文件位置指示器和当前解析状态(如果有)stream
并将它们存储在指向的对象中pos
。存储的值只对输入有意义fsetpos
。
参数
流 |
- |
文件流来检查 |
---|---|---|
岗位 |
- |
指向fpos_t对象以存储文件位置指示符的指针 |
返回值
0
一旦成功,否则非零值。
例
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
int main(void)
{
// prepare a file holding 4 values of type double
enum {SIZE = 4};
FILE* fp = fopen("test.bin", "wb");
assert(fp);
int rc = fwrite((double[SIZE]){1.1, 2.2, 3.3, 4.4}, sizeof(double), SIZE, fp);
assert(rc == SIZE);
fclose(fp);
// demo using fsetpos to return to the beginning of a file
fp = fopen("test.bin", "rb");
fpos_t pos;
fgetpos(fp, &pos); // store start of file in pos
double d;
rc = fread(&d, sizeof d, 1, fp); // read the first double
assert(rc == 1);
printf("First value in the file: %.1f\n", d);
fsetpos(fp,&pos); // move file position back to the start of the file
rc = fread(&d, sizeof d, 1, fp); // read the first double again
assert(rc == 1);
printf("First value in the file again: %.1f\n", d);
fclose(fp);
// demo error handling
rc = fsetpos(stdin, &pos);
if(rc) perror("could not fsetpos stdin");
}
输出:
First value in the file: 1.1
First value in the file again: 1.1
could not fsetpos stdin: Illegal seek
参考
- C11标准(ISO / IEC 9899:2011):
- 7.21.9.1 fgetpos函数(p:336)
- C99标准(ISO / IEC 9899:1999):
- 7.19.9.1 fgetpos函数(p:302)
- C89 / C90标准(ISO / IEC 9899:1990):
- 4.9.9.1 fgetpos函数