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SEEK.C
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─────Run-Time Library───────────────────────────────────────────────────────
/* SEEK.C illustrates low-level file I/O functions including:
* _filelength _lseek _tell
*/
#include <io.h>
#include <conio.h>
#include <stdio.h>
#include <fcntl.h> /* _O_ constant definitions */
#include <process.h>
void error( char *errmsg );
void main()
{
int handle, ch;
unsigned count;
long position, length;
char buffer[2], fname[80];
/* Get file name and open file. */
do
{
printf( "Enter file name: " );
gets( fname );
handle = _open( fname, _O_BINARY | _O_RDONLY );
} while( handle == -1 );
/* Get and print length. */
length = _filelength( handle );
printf( "\nFile length of %s is: %ld\n\n", fname, length );
/* Report the character at a specified position. */
do
{
printf( "Enter integer position less than file length: " );
scanf( "%ld", &position );
} while( position > length );
_lseek( handle, position, SEEK_SET );
if( _read( handle, buffer, 1 ) == -1 )
error( "Read error" );
printf( "Character at byte %ld is ASCII %u ('%c')\n\n",
position, *buffer, *buffer );
/* Search for a specified character and report its position. */
_lseek( handle, 0L, SEEK_SET); /* Set to position 0 */
printf( "Type character to search for: " );
ch = _getche();
/* Read until character is found. */
do
{
if( (count = _read( handle, buffer, 1 )) == -1 )
error( "Read error" );
} while( (*buffer != (char)ch) && count );
/* Report the current position. */
position = _tell( handle );
if( count )
printf( "\nFirst ASCII %u ('%c') is at byte %ld\n",
ch, ch, position );
else
printf( "\nASCII %u ('%c') not found\n", ch, ch );
_close( handle );
exit( 0 );
}
void error( char *errmsg )
{
perror( errmsg );
exit( 1 );
}
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