fgetpos
From cppreference.com
| Defined in header <stdio.h>
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| (until C99) | ||
| (since C99) | ||
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.
Parameters
| stream | - | file stream to examine |
| pos | - | pointer to a fpos_t object to store the file position indicator to |
Return value
0 upon success, nonzero value otherwise.
Example
Run this code
#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"); }
Output:
First value in the file: 1.1 First value in the file again: 1.1 could not fsetpos stdin: Illegal seek
References
- C11 standard (ISO/IEC 9899:2011):
- 7.21.9.1 The fgetpos function (p: 336)
- C99 standard (ISO/IEC 9899:1999):
- 7.19.9.1 The fgetpos function (p: 302)
- C89/C90 standard (ISO/IEC 9899:1990):
- 4.9.9.1 The fgetpos function
See also
| returns the current file position indicator (function) | |
| moves the file position indicator to a specific location in a file (function) | |
| moves the file position indicator to a specific location in a file (function) |