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RECORDS2.C
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─────Run-Time Library───────────────────────────────────────────────────────
/* RECORDS2.C illustrates reading and writing of file records with the
* following functions:
* fgetpos fsetpos
*
* See RECORDS1.C for a version using fseek, rewind, and ftell.
*/
#include <stdio.h>
#include <io.h>
/* File record */
struct RECORD
{
int integer;
long doubleword;
double realnum;
} filerec = { 0, 1, 10000000.0 };
void main()
{
int c, newrec;
size_t recsize = sizeof( filerec );
FILE *recstream;
fpos_t recpos;
/* Create and open temporary file. */
recstream = tmpfile();
/* Write 10 unique records to file. */
for( c = 0; c < 10; c++ )
{
++filerec.integer;
filerec.doubleword *= 3;
filerec.realnum /= (c + 1);
fwrite( &filerec, recsize, 1, recstream );
}
/* Find a specified record. */
do
{
printf( "Enter record betweeen 1 and 10 (or 0 to quit): " );
scanf( "%d", &newrec );
/* Find and display valid records. */
if( (newrec >= 1) && (newrec <= 10) )
{
recpos = (fpos_t)((newrec - 1) * recsize);
fsetpos( recstream, &recpos );
fread( &filerec, recsize, 1, recstream );
printf( "Integer:\t%d\n", filerec.integer );
printf( "Doubleword:\t%ld\n", filerec.doubleword );
printf( "Real number:\t%.2f\n", filerec.realnum );
}
} while( newrec );
/* Starting at first record, scan each for specific value. */
recpos = (fpos_t)0;
fsetpos( recstream, &recpos );
do
fread( &filerec, recsize, 1, recstream );
while( filerec.doubleword < 1000L );
fgetpos( recstream, &recpos );
printf( "\nFirst doubleword above 1000 is %ld in record %d\n",
filerec.doubleword, recpos / recsize );
/* Close and delete temporary file. */
_rmtmp();
}
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