Installation

With LuaRocks

Clone the repo, then, from this directory :

luarocks make

Manually

ln -s ltl.moon SOMEWHERE/IN/YOUR/PATH/ltl

Or, if you’d like not to depend on MoonScript at runtime :

echo '#!/usr/bin/env lua[jit]' > ltl.lua && moonc -p ltl.moon >> ltl.lua && chmod +x ltl.lua [&& mv ltl.lua SOMEWHERE/IN/YOUR/PATH/ltl]

Usage

ltl will write to stdout the result of the code given as argument. If this code returns a string, it will be output to stdout ; if it returns a table, it will be output to stdout line by line (with tconcat(RESULT, '\n')) ; if it returns a function (that must be an iterator), it will be iterated, and the result printed line by line.

ltl may operate as a filter thanks to the special IN table (that wraps io.stdin), reading the file given as input (or stdin) if applicable.

Arguments description

echo SOMETHING | ltl [-i] [-n] [--clean] "LUA CODE" [FILE]
echo ANYTHINGELSE | ltl -m [-i] [--clean] "MOONSCRIPT CODE" [FILE]

-m : use MoonScript instead of Lua.

-i : in-place (like sed) ; only means something if FILE is defined.

-n : don't add newline at end (like echo)

--clean : By default, properties of lpeg, coroutine, table, math (and moon for moonscript) are injected in the metatable index of the global environment, for convenience in a shell context ; re is imported. Moreover, a special proxy table is created, named IN (see below). All that is omitted when using --clean.

LUA CODE or MOONSCRIPT CODE : a string containing the "program" to execute.

FILE : optional argument indicating from which file to read ; if you leave it empty, but use IN, input will be read from stdin (and if no stdin, from user input).

IN

IN is a special table that represents stdin. It can be used :

• by calling it, as an iterator over lines : for l in IN is an equivalent of for l in io.stdin:lines() ;
• by indexing it, as a table of lines : IN[2] is the 2nd line ;
• by invoking a string method on it, as a string : ltl "print(IN)" will output the content of stdin, ltl -m 'IN\gsub "a", "b"' will output the content of stdin with all "a" replaced by "b".

Examples

Three ways to get the square root of numbers from 1 to 10 :

$ seq 1 10 | ltl -m '[math.sqrt i for i in IN]'

or

$ ltl -m '[math.sqrt i for i = 1, 10]'

or (less ram, more cpu)

$ ltl -m 'wrap -> yield math.sqrt i for i = 1, 10'
1
1.4142135623731
1.7320508075689
2
2.2360679774998
2.4494897427832
2.6457513110646
2.8284271247462
3
3.1622776601684

String substitution (here, all empty lines are removed) :

$ echo '13\nabc\n\n05' | ltl -n -m 'IN\gsub("\n[\n]+", "\n")'
13
abc
05

Pattern-matching thanks to lpeg :

$ echo '13\nabc\n05' | ltl 'num = locale().digit; function non(x) return P(1) - x end; function maybe(x) return x^-1 end; return Ct((C(num^2) * maybe(non(num)^1))^1):match(tostring(IN))'
13
05

$ echo '13abc\n05' | ltl -m '
num = locale!.digit
non = => P(1) - self
maybe = => self^-1
Ct((C(num^2) * maybe non(num)^1)^1)\match tostring IN
'
13
05

Regex (p is a pretty-printing function from moon) :

$ ltl -m 'p {re.match "the number 423 is odd}", "({%a+} / .)*"'
{
    [1] = "the"
    [2] = "number"
    [3] = "is"
    [4] = "odd"
}