How do you construct a read-write pipe with lua?

Question

I\'d like to do the equivalent of:

foo=$(echo \"$foo\"|someprogram)

within lua -- ie, I\'ve got a variable containing a bunch of text, and

Answer 1

Here is how I solved the problem, it require lua posix.

          p = require 'posix'
          local r,w = p.pipe()
          local r1,w1 = p.pipe()
          local cpid = p.fork()
          if cpid == 0 then -- child reads from pipe                                     
             w:close()
             r1:close()
             p.dup(r, io.stdin)
             p.dup(w1 ,io.stdout)
             p.exec('./myProgram')
             r:close()
             w1:close()
             p._exit(0)
          else -- parent writes to pipe                                                  
             IN = r1
             OUT = w
          end

During myProgram execution, you'l read and write from normal io and after this part of code you just have to write/read on IN and OUT to comunicate with child program.