End of Life Ruby 3.0 has reached end of life and gets no more fixes. Switch to Ruby 4.0 →
instance method
IO#sysseek
ios.sysseek(offset, whence=IO::SEEK_SET) → integer
io.c
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static VALUE
rb_io_sysseek(int argc, VALUE *argv, VALUE io)
{
VALUE offset, ptrname;
int whence = SEEK_SET;
rb_io_t *fptr;
off_t pos;
if (rb_scan_args(argc, argv, "11", &offset, &ptrname) == 2) {
whence = interpret_seek_whence(ptrname);
}
pos = NUM2OFFT(offset);
GetOpenFile(io, fptr);
if ((fptr->mode & FMODE_READABLE) &&
(READ_DATA_BUFFERED(fptr) || READ_CHAR_PENDING(fptr))) {
rb_raise(rb_eIOError, "sysseek for buffered IO");
}
if ((fptr->mode & FMODE_WRITABLE) && fptr->wbuf.len) {
rb_warn("sysseek for buffered IO");
}
errno = 0;
pos = lseek(fptr->fd, pos, whence);
if (pos < 0 && errno) rb_sys_fail_path(fptr->pathv);
return OFFT2NUM(pos);
}
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.
Example
f = File.new("testfile") f.sysseek(-13, IO::SEEK_END) #=> 53 f.sysread(10) #=> "And so on."