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instance method

IO#seek

seek(offset, whence = IO::SEEK_SET) → 0

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);
}

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:

Example

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

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

Example

f = File.open('t.txt')
f.tell            # => 0
f.seek(0, :END)   # => 0  # Repositions to stream end.
f.tell            # => 70
f.seek(-20, :END) # => 0
f.tell            # => 50
f.seek(-40, :END) # => 0
f.tell            # => 30

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

Example

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

Related: IO#pos=, IO#tell.

See also #scroll_forward #set_encoding #scroll_backward #set_encoding_by_bom also in 4.1 · 4.0 · 3.4 · 3.3 · 3.2 · 3.0

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