The following examples relate to allowing Lua to interact with the shell, such as for shell scripting.

[!] VersionNotice: The below code pertains to an older Lua version, Lua 4. Some of it does not run as is under Lua 5.

Piping from command

This reads output from a process via a pipe. There is a way to make this work on Windows too (see PipesOnWindows, not needed for Lua 5.1.2, see below).

-- Perform a shell command and return its output
-- c: command
-- returns
-- o: output
function shell(c)
 local input = _INPUT
 local o, h
 h = readfrom("|" .. c)
 o = read("*a")
 closefile(h)
 _INPUT = input
 return o
end

On lua5.0.2 I think it should be something like:

function shell(c)
 local o, h
 h = assert(io.popen(c,"r"))
 o = h:read("*all")
 h:close()
 return o
end

Lua 5.1.2: io.popen runs fine under Windows XP "out-of-the-box", even from within a non-DOS application --AndreasRozek

Process files in command-line arguments

A typical thing to want to do in a command-line utility is to process each file given on the command line. Here's a function to encapsulate this process:

-- Process all the files specified on the command-line with function f
-- name: the name of the file being read
-- i: the number of the argument
function processFiles(f)
 for i = 1, getn(arg) do
 if arg[i] == "-" then readfrom()
 else readfrom(arg[i])
 end
 file = arg[i]
 f(arg[i], i)
 readfrom() -- close file, if not already closed
 end
end

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Last edited April 17, 2007 11:26 am GMT (diff)