Obtains the file position indicator and the current parse state (if any) for the file stream stream and stores them in the object pointed to by pos. The value stored is only meaningful as the input to fsetpos.
[edit] Parameters stream - file stream to examine pos - pointer to a fpos_t object to store the file position indicator to [edit] Return valueâ0â upon success, nonzero value otherwise.
[edit] Example#include <assert.h>
#include <stdio.h>
#include <stdlib.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");
}
Output:
First value in the file: 1.1 First value in the file again: 1.1 could not fsetpos stdin: Illegal seek[edit] References
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