Haskell command line text processor
Tool to quickly compile and run haskell streaming text processors on the command line.
Features a powerful way of working quickly with JSON.
Poor man's tac:
> seq 3 | hsl reverse
3
2
1
The input is a [Text], a list of lines.
> echo '!LSH olleH' | hsl 'fmap T.reverse'
Hello HSL!
The output is also an array of lines... but it could also be an array of tuples, in which case the tuples are displayed as tab-separated columns.
> printf 'helloWorld\nnicePlanet\n' | hsl "fmap (break isUpper)"
hello World
nice Planet
Or a single value...
> printf 'literary\ncheeseburger' | hsl 'maximumBy (comparing T.length) . concatMap T.words'
cheeseburger
Full Haskell syntax is supported. Go crazy!
> printf "hello\nworld\n" | hsl 'take 2 . repeat . filter (T.isPrefixOf "w")'
world
world
A few builtins, such as hist, are provided for convenience.
cat src/HSL/*.hs | hsl 'take 5 . sortOnR snd . hist . concatMap T.words'
= 56
-> 50
:: 24
Datum 21
b, 21
You can add your own builtins to src/HSL/Stdlib.hs. Send us yours in a pull request!
One of HSL's most useful builtin is json. It's like cut, but for JSON!
More concretely, if you have a file with one JSON expression per line, json lets you easily specify a path from which to extract elements.
> cat cat_memes.json
{"name": "nyan", "year": 2011}
{"name": "longcat", "year": 2007}
{"name": "ceiling cat", "year": 2006}
{"name": "invisible bike cat", "year": 2008}
> cat cat_memes.json | hsl 'sort . json i "year"'
2006
2007
2008
2011
The i argument specifies the type of the result. i (Int), t (Text)
and f (Float) are provided for this purpose. The following are equivalent:
echo '[[1,2],[3,4]]' | hsl 'json (undefined::[(Int,Int)]) ""'
1 2
3 4
echo '[[1,2],[3,4]]' | hsl 'json [(i,i)] ""'
1 2
3 4
The empty string in the above example is an empty path, referring to the entire JSON expression. The general syntax for paths is illustrated in the following example:
> echo '{"a":{"b":["Hello","World"]}}' | hsl 'json t "a b 0"'
Hello
If you need to extract more than one value per line, use json2 or json3.
> echo '{"born":1938, "age":75}' | hsl 'fmap (uncurry (+)) . json2 (i,i) "born" "age"'
2013
The function tabs is provided to read \t separated input. It works just like json,
except you don't need to provide keys:
> printf 'a 10\nb 11\na 12' | hsl 'tally . tabs (t,i)'
a 22
b 11
> git clone 'https://github.com/ssadler/hsl.git' && cd hsl
> # Install dependencies... You probably already have them (?)
> echo 'alias hsl="'`pwd`'/hsl"' >> ~/.bashrc