sysseek(...)
public
Seeks to a given offset in the stream according to the value of
whence (see IO#seek for
values of whence). Returns the new offset into the file.
f = File.new("testfile")
f.sysseek(-13, IO::SEEK_END)
f.sysread(10)
Show source
/*
* call-seq:
* ios.sysseek(offset, whence=SEEK_SET) => integer
*
* Seeks to a given <i>offset</i> in the stream according to the value
* of <i>whence</i> (see <code>IO#seek</code> for values of
* <i>whence</i>). Returns the new offset into the file.
*
* f = File.new("testfile")
* f.sysseek(-13, IO::SEEK_END) #=> 53
* f.sysread(10) #=> "And so on."
*/
static VALUE
rb_io_sysseek(argc, argv, io)
int argc;
VALUE *argv;
VALUE io;
{
VALUE offset, ptrname;
int whence = SEEK_SET;
OpenFile *fptr;
off_t pos;
if (rb_scan_args(argc, argv, "11", &offset, &ptrname) == 2) {
whence = NUM2INT(ptrname);
}
pos = NUM2OFFT(offset);
GetOpenFile(io, fptr);
if ((fptr->mode & FMODE_READABLE) && READ_DATA_BUFFERED(fptr->f)) {
rb_raise(rb_eIOError, "sysseek for buffered IO");
}
if ((fptr->mode & FMODE_WRITABLE) && (fptr->mode & FMODE_WBUF)) {
rb_warn("sysseek for buffered IO");
}
pos = lseek(fileno(fptr->f), pos, whence);
if (pos == -1) rb_sys_fail(fptr->path);
clearerr(fptr->f);
return OFFT2NUM(pos);
}