Method: IO#seek

Defined in:

io.c

#seek(offset, whence = IO::SEEK_SET) ⇒ 0

Seeks to the position given by integer offset (see Position) and constant whence, which is one of:

• :CUR or IO::SEEK_CUR: Repositions the stream to its current position plus the given offset:

  f = File.open('t.txt')
  f.tell            # => 0
  f.seek(20, :CUR)  # => 0
  f.tell            # => 20
  f.seek(-10, :CUR) # => 0
  f.tell            # => 10
  f.close
  

• :END or IO::SEEK_END: Repositions the stream to its end plus the given offset:

  f = File.open('t.txt')
  f.tell            # => 0
  f.seek(0, :END)   # => 0  # Repositions to stream end.
  f.tell            # => 52
  f.seek(-20, :END) # => 0
  f.tell            # => 32
  f.seek(-40, :END) # => 0
  f.tell            # => 12
  f.close
  

• :SET or IO:SEEK_SET: Repositions the stream to the given offset:

  f = File.open('t.txt')
  f.tell            # => 0
  f.seek(20, :SET) # => 0
  f.tell           # => 20
  f.seek(40, :SET) # => 0
  f.tell           # => 40
  f.close
  

Related: IO#pos=, IO#tell.

Returns:

• (0)

# File 'io.c', line 2521

static VALUE
rb_io_seek_m(int argc, VALUE *argv, VALUE io)
{
    VALUE offset, ptrname;
    int whence = SEEK_SET;

    if (rb_scan_args(argc, argv, "11", &offset, &ptrname) == 2) {
        whence = interpret_seek_whence(ptrname);
    }

    return rb_io_seek(io, offset, whence);
}