Gray Soft / The Standard Library

13
OCT
2008
The Secret Shell Helper

Someone pops onto the Ruby Talk mailing list fairly regularly asking how to break up content like:
```
one "two" "a longer three"
```
They expect to end with a three element Array, where the third item will contain spaces. They generally expect the quotes will have been removed as well.

If your needs are very, very simple you may be able to handle this with a regular expression:
```
data = 'one "two" "a longer three"'
p data.scan(/"([^"]*)"|(\S+)/).flatten.compact
# >> ["one", "two", "a longer three"]
```
That just searches for either a set of quotes with some non-quote characters between them or a run of non-whitespace characters. Those are the two possibilities for the fields. Note that the two separate capture here mean scan() will returns contents in the form:
```
[[nil, "one"], ["two", nil], ["a longer three", nil]]
```
That's why I added a flatten() and compact() to get down to the actual matches.

The regular expression approach can get pretty complex though if any kind of escaping for quotes is involved. When that happens, you may need to step up to a parser.
Read more…
In: The Standard Library | Tags: FasterCSV, Hidden Features & Unix Shells | 1 Comment
29
FEB
2008
A Bug, Today Only

I had to debug some tests that just started failing first thing this morning. I guess I should have procrastinated though, because they would have magically fixed themselves tomorrow morning. The cause of the one day only bug: Leap Year Day, of course.

If you run the following code on a day like today, February 29th 2008, Date will choke on your invalid date:
```
require "date"  

class Date
  # Returns a Date in the past +year_offset+ years ago.
  def self.years_ago(year_offset)
    now = today
    Date.civil(now.year - year_offset, now.month, now.day)
  end
end

puts Date.years_ago(1)
```
I came up with the following fix, which is accurate enough for my purposes:
```
require "date"

class Date   # Returns a Date in the past +year_offset+ years ago.
  def self.years_ago(year_offset)
    today - 365 * year_offset
  end
end

puts Date.years_ago(1)
```
I'm not 100% sure that covers all cases though, so use with caution. Date's are tricky business!
In: The Standard Library | Tags: Bugs, Date/Time & Leap Year | 1 Comment
30
JUL
2006
PStore Meets YAML

I love the PStore standard library. It's a very graceful interface to get some fairly robust serialized mini-database handling in just a few lines. With it you get:
1. Transactions with commit and rollbacks (automatic on exception).
2. File locking, shared and exclusive.
3. Multiprocessing safety.
PStore does even more, including some file mode checking and MD5 hashing to avoid unneeded writes, but the above are the major selling points for me.

Now, if I had to level any one complaint at PStore, it would be that because it uses Marshal under the hood it doesn't create files you can easily browse or tweak by hand. (Marshal is a feature, don't get me wrong. It's fast, which is very helpful.) Sometimes though I want PStore protection with the YAML file format.

I'm embarrassed to admit that I use to use a hack for this:
```
require "pstore"
require "yaml"
class PStore; Marshal = YAML; end
```
That just redefines the Marshal constant in a scope that should only alter PStore. The library only uses dump() and load() and those methods work the same with Marshal and YAML.
Read more…
In: The Standard Library | Tags: Hidden Features | 2 Comments

8

JUL
2006

The Books are Wrong About Logger

I've read several books that introduced the standard Logger library and they all agree on one thing: you can't customize the output. That's so last version in thinking! Behold…

Here's a trivial Logger script, showing basic functionality:

#!/usr/bin/env ruby -w

require "logger"

def expensive_error_report
  sleep 3  # Heavy Computation Simulation (patent pending)
  "YOU BROKE IT!"
end

log       = Logger.new(STDOUT)
log.level = Logger::INFO  # set out output level above the DEBUG default

log.debug("We're not in the verbose debug mode.")
log.info("We do see informative logs though.")
if log.error?  # check that this will be printed, before waste time
  log.error(expensive_error_report)
end

If you run that you will see:

I, [2006-07-08T11:17:19.531943 #340]  INFO -- : We do see informative logs though.
E, [2006-07-08T11:17:22.532424 #340] ERROR -- : YOU BROKE IT!

Now everyone has always known you can format the date and time display using a strftime() compatible pattern:

#!/usr/bin/env ruby -w

require "logger"

def expensive_error_report
  sleep 3
  "YOU BROKE IT!"
end

log                 = Logger.new(STDOUT)
log.level           = Logger::INFO
log.datetime_format = "%Y-%m-%d %H:%M "  # simplify time output

log.debug("We're not in the verbose debug mode.")
log.info("We do see informative logs though.")
if log.error?
  log.error(expensive_error_report)
end

The Standard Library

13

The Secret Shell Helper

29

A Bug, Today Only

30

PStore Meets YAML

8

The Books are Wrong About Logger

4

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