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instance method

File#truncate

(::int length) -> 0

truncate(size) → 0

static VALUE
rb_file_truncate(VALUE obj, VALUE len)
{
    rb_io_t *fptr;
    struct ftruncate_arg fa;

    fa.pos = NUM2OFFT(len);
    GetOpenFile(obj, fptr);
    if (!(fptr->mode & FMODE_WRITABLE)) {
        rb_raise(rb_eIOError, "not opened for writing");
    }
    rb_io_flush_raw(obj, 0);
    fa.fd = fptr->fd;
    if ((int)rb_io_blocking_region(fptr, nogvl_ftruncate, &fa) < 0) {
        rb_sys_fail_path(fptr->pathv);
    }
    return INT2FIX(0);
}

Adjusts the size of self to the given size, regardless of the current position; does not adjust the position:

Example

filepath = '/tmp/t.tmp'
file = File.new(filepath, 'w+')
file.write('0123456789')
file.truncate(5)
file.pos  # => 10
file.rewind
file.read # => "01234"

Pads with null characters if necessary:

Example

file.truncate(10)
file.pos  # => 5
file.rewind
file.read # => "01234\u0000\u0000\u0000\u0000\u0000"
# Clean up.
file.close
File.delete(filepath)

See also .truncate #size #mtime also in 4.0 · 3.4 · 3.3 · 3.2 · 3.1 · 3.0

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