Skip to main content

Ruby - ARGF interesting but destructive

[Update 2012-07-08] I reviewed the ARGF source code and it explicitly closes the file. This is silly nonsense because (a) #close is supposed to perform a File::close and then advance to the next file in the list. (b) #close and #skip are not documented as aliases (c) the doc for #skip does not say anything about side effects.

Thanks to the guys at pragprog I have been rereading pickaxe. And in the process I found the ARGF class. It seemed pretty interesting because it was supposed to process ARGV as if all of the arguments represented files. (state of the files not withstanding).

The problem, however, is that it just feels improperly implemented. The first time you do anything with ARGF is has already opened the first file. And when you are on the last file where is no way to know other than checking closed? or fileno against the previous iteration. For example I would expect something like this:

[sourcecode language="ruby"]
while ARGF.more?
ARGF.skip
# and then do some stuff to the file
end
[/sourcecode]

Instead you have to do this:

[sourcecode language="ruby"]
while not ARGF.file.closed?
# do some stuff to the file
ARGF.skip
end
[/sourcecode]

or the while loop could be:

[sourcecode language="ruby"]
while ARGF.argv.size
[/sourcecode]

I suppose there is no much difference between the first example and the second from a structure perspective, however, there are side effects. Once you start to use ARGF the first file is opened. That might be a good thing and it might be bad. But it may also mean handling exceptions in more than one place. It certainly feels more verbose. Specially if you want to count the number of params by reusing ARGV.

The big floppy issue, however, is that ARGF is destructive.  Since ARGF connects to ARGV via a reference meaning that external code can alter the ARGV and the effects will be reflected in ARGF. The opposite is true too.  When skip'ing over parameters ARGF appears to be removing the file from ARGV. Meaning that you cannot do anything with argv/ARGV after the fact as it has been consumed. (This side effect is never mentioned; in fact the documentation for ARGF never even hints at this.)

The third piece of code makes processing easier but unexpected.

Comments

Popular posts from this blog

Entry level cost for CoreOS+Tectonic

CoreOS and Tectonic start their pricing at 10 servers. Managed CoreOS starts at $1000 per month for those first 10 servers and Tectonic is $5000 for the same 10 servers. Annualized that is $85K or at least one employee depending on your market. As a single employee company I'd rather hire the employee. Specially since I only have 3 servers.

The pricing is biased toward the largest servers with the largest capacities; my dual core 32GB i5 IntelNuc can never be mistaken for a 96-CPU dual or quad core DELL

If CoreOS does not figure out a different barrier of entry they are going to follow the Borland path to obscurity.

UPDATE 2017-10-30: With gratitude the CoreOS team has provided updated information on their pricing, however, I stand by my conclusion that the effective cost is lower when you deploy monster machines. The cost per node of my 1 CPU Intel NUC is the same as a 96 CPU server when you get beyond 10 nodes. I'll also reiterate that while my pricing notes are not currently…

eGalax touch on default Ubuntu 14.04.2 LTS

I have not had success with the touch drivers as yet.  The touch works and evtest also seems to report events, however, I have noticed that the button click is not working and no matter what I do xinput refuses to configure the buttons correctly.  When I downgraded to ubuntu 10.04 LTS everything sort of worked... there must have been something in the kermel as 10.04 was in the 2.6 kernel and 4.04 is in the 3.x branch.

One thing ... all of the documentation pointed to the wrong website or one in Taiwanese. I was finally able to locate the drivers again: http://www.eeti.com.tw/drivers_Linux.html (it would have been nice if they provided the install instructions in text rather than PDF)
Please open the document "EETI_eGTouch_Programming_Guide" under the Guide directory, and follow the Guidline to install driver.
download the appropriate versionunzip the fileread the programming manual And from that I'm distilling to the following: execute the setup.sh answer all of the questio…

Prometheus vs Bosun

In conclusion... while Bosun(B) is still not the ideal monitoring system neither is Prometheus(P).

TL;DR;

I am running Bosun in a Docker container hosted on CoreOS. Fleet service/unit files keep it running. However in once case I have experienced at least one severe crash as a result of a disk full condition. That it is implemented as part golang, java and python is an annoyance. The MIT license is about the only good thing.

I am trying to integrate Prometheus into my pipeline but losing steam fast. The Prometheus design seems to desire that you integrate your own cache inside your application and then allow the server to scrape the data, however, if the interval between scrapes is shorter than the longest transient session of your application then you need a gateway. A place to shuttle your data that will be a little more persistent.

(1) storing the data in my application might get me started more quickly
(2) getting the server to pull the data might be more secure
(3) using a push g…