fgetpos

在头文件中定义
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）：