foreach

/*
 *  call-seq:
 *     IO.foreach(name, sep_string=$/) {|line| block }   => nil
 *  
 *  Executes the block for every line in the named I/O port, where lines
 *  are separated by <em>sep_string</em>.
 *     
 *     IO.foreach("testfile") {|x| print "GOT ", x }
 *     
 *  <em>produces:</em>
 *     
 *     GOT This is line one
 *     GOT This is line two
 *     GOT This is line three
 *     GOT And so on...
 */     

static VALUE
rb_io_s_foreach(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE fname;
    struct foreach_arg arg;

    rb_scan_args(argc, argv, "11", &fname, &arg.sep);
    SafeStringValue(fname);

    if (argc == 1) {
        arg.sep = rb_default_rs;
    }
    else if (!NIL_P(arg.sep)) {
        StringValue(arg.sep);
    }
    arg.io = rb_io_open(StringValueCStr(fname), "r");
    if (NIL_P(arg.io)) return Qnil;

    return rb_ensure(io_s_foreach, (VALUE)&arg, rb_io_close, arg.io);
}