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fsetpos

From cppreference.com
< c‎ | io
Revision as of 08:21, 1 May 2014 by Newatthis (Talk | contribs)

Defined in header <stdio.h>
int fsetpos( FILE *stream, const fpos_t *pos );

Sets the file position indicator for the file stream stream to the value pointed to by pos.

Contents

Parameters

stream - file stream to modify
pos - pointer to a fpos_t object to use as new value of file position indicator

Return value

0 upon success, nonzero value otherwise.

Example

fsetpos with error checking

#include <stdio.h>
#include <stdlib.h>
 
int main(void)
{
    /* Prepare an array of f-p values. */
    #define SIZE 5
    double A[SIZE] = {1.,2.,3.,4.,5.};
    /* Write array to a file. */
    FILE * fp = fopen("test.bin", "wb");
    fwrite(A,sizeof(double),SIZE,fp);
    fclose (fp);
 
    /* Read the f-p values into array B. */
    double B[SIZE];
    fp = fopen("test.bin","rb");
    fpos_t pos;
    if (fgetpos(fp,&pos) != 0)      /* current position: start of file */
    {
       perror("fgetpos()");
       fprintf(stderr,"fgetpos() failed in file %s at line # %d\n", __FILE__,__LINE__-3);
       exit(EXIT_FAILURE);
    }
 
    int ret_code = fread(B,sizeof(double),1,fp);   /* read one f-p value */
    /* current position: after reading one f-p value */
    printf("%.1f\n", B[0]);   /* print one f-p value */
 
    if (fsetpos(fp,&pos) != 0)   /* reset current position to start of file */
    {
       if (ferror(fp))
       {
          perror("fsetpos()");
          fprintf(stderr,"fsetpos() failed in file %s at line # %d\n", __FILE__,__LINE__-5);
          exit(EXIT_FAILURE);
       }
    }
 
    ret_code = fread(B,sizeof(double),1,fp);   /* reread first f-p value */
    printf("%.1f\n", B[0]);                    /* print one f-p value    */
    fclose(fp);
 
    return EXIT_SUCCESS; 
}

Output:

1.0
1.0

See also

gets the file position indicator
(function) [edit]
returns the current file position indicator
(function) [edit]
moves the file position indicator to a specific location in a file
(function) [edit]
C++ documentation for fsetpos