_read
Reads data from a file.
int_read(inthandle**,void*buffer,unsignedintcount);**
| Routine | Required Header | Compatibility |
| _read | <io.h> | Win 95, Win NT |
For additional compatibility information, see Compatibility in the Introduction.
Libraries
| LIBC.LIB | Single thread static library, retail version |
| LIBCMT.LIB | Multithread static library, retail version |
| MSVCRT.LIB | Import library for MSVCRT.DLL, retail version |
Return Value
_read returns the number of bytes read, which may be less than count if there are fewer than count bytes left in the file or if the file was opened in text mode, in which case each carriage return–linefeed (CR-LF) pair is replaced with a single linefeed character. Only the single linefeed character is counted in the return value. The replacement does not affect the file pointer.
If the function tries to read at end of file, it returns 0. If the handle is invalid, or the file is not open for reading, or the file is locked, the function returns –1 and sets errno to EBADF.
Parameters
handle
Handle referring to open file
buffer
Storage location for data
count
Maximum number of bytes
Remarks
The _read function reads a maximum of count bytes into buffer from the file associated with handle. The read operation begins at the current position of the file pointer associated with the given file. After the read operation, the file pointer points to the next unread character.
If the file was opened in text mode, the read terminates when _read encounters a CTRL+Z character, which is treated as an end-of-file indicator. Use _lseek to clear the end-of-file indicator.
Example
/* READ.C: This program opens a file named
* READ.C and tries to read 60,000 bytes from
* that file using _read. It then displays the
* actual number of bytes read from READ.C.
*/
#include <fcntl.h> /* Needed only for _O_RDWR definition */
#include <io.h>
#include <stdlib.h>
#include <stdio.h>
char buffer[60000];
void main( void )
{
int fh;
unsigned int nbytes = 60000, bytesread;
/* Open file for input: */
if( (fh = _open( "read.c", _O_RDONLY )) == -1 )
{
perror( "open failed on input file" );
exit( 1 );
}
/* Read in input: */
if( ( bytesread = _read( fh, buffer, nbytes ) ) <= 0 )
perror( "Problem reading file" );
else
printf( "Read %u bytes from file\n", bytesread );
_close( fh );
}
Output
Read 775 bytes from file