Question

我想做相同的事情：

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

在lua中 - 也就是说，我有一个包含一堆文本的变量，我想通过一个过滤器运行它（在python中实现）。

任何提示？

补充：真的很想不使用临时文件

Answer 1

Lua标准库中没有任何内容允许这样做。

Here is an in-depth exploration of the difficulties of doing bidirectional communication properly，以及建议的解决方案：

如果可能，将流的一端（输入或输出）重定向到文件。即：
fp = io.popen("foo >/tmp/unique", "w")
fp:write(anything)
fp:close()
fp = io.open("/tmp/unique")
x = read("*a")
fp:close()

您可能会对this extension感兴趣，它会在os和io命名空间中添加函数，以便与子流程进行双向通信。

Answer 2

啊哈，一个可能更好的解决方案：

require('posix')
require('os')
require('io')

function splat_popen(data,cmd)
   rd,wr = posix.pipe()
   io.flush()
   child = posix.fork()
   if child == 0 then
      rd:close()
      wr:write(data)
      io.flush()
      os.exit(1)
   end
   wr:close()

   rd2,wr2 = posix.pipe()
   io.flush()
   child2 = posix.fork()
   if child2 == 0 then
      rd2:close()
      posix.dup(rd,io.stdin)
      posix.dup(wr2,io.stdout)
      posix.exec(cmd)
      os.exit(2)
   end
   wr2:close()
   rd:close()

   y = rd2:read("*a")
   rd2:close()

   posix.wait(child2)
   posix.wait(child)

   return y
end

munged=splat_popen("hello, world","/usr/games/rot13")
print("munged: "..munged.." !")

Answer 3

只要您的Lua支持io.popen，这个问题就很容易了。解决方案正如您所概述的那样，除了代替$(...)之外，您需要一个像这样的函数：

function os.capture(cmd, raw)
  local f = assert(io.popen(cmd, 'r'))
  local s = assert(f:read('*a'))
  f:close()
  if raw then return s end
  s = string.gsub(s, '^%s+', '')
  s = string.gsub(s, '%s+$', '')
  s = string.gsub(s, '[\n\r]+', ' ')
  return s
end

然后你可以打电话

local foo = ...
local cmd = ("echo $foo | someprogram"):gsub('$foo', foo)
foo = os.capture(cmd)

我一直这样做。这是一个用于形成命令的相关有用函数：

local quote_me = '[^%w%+%-%=%@%_%/]' -- complement (needn't quote)
local strfind = string.find

function os.quote(s)
  if strfind(s, quote_me) or s == '' then
    return "'" .. string.gsub(s, "'", [['"'"']]) .. "'"
  else
    return s
  end
end

Answer 4

我在尝试做同样的事情并且从未找到一个好的解决方案时偶然发现了这篇文章，请参阅下面的代码，了解我如何解决我的问题。此实现允许用户访问stdin，stdout，stderr并获取返回状态代码。一个简单的包装器被称为简单的管道调用。

require("posix")

--
-- Simple popen3() implementation
--
function popen3(path, ...)
    local r1, w1 = posix.pipe()
    local r2, w2 = posix.pipe()
    local r3, w3 = posix.pipe()

    assert((w1 ~= nil or r2 ~= nil or r3 ~= nil), "pipe() failed")

    local pid, err = posix.fork()
    assert(pid ~= nil, "fork() failed")
    if pid == 0 then
        posix.close(w1)
        posix.close(r2)
        posix.dup2(r1, posix.fileno(io.stdin))
        posix.dup2(w2, posix.fileno(io.stdout))
        posix.dup2(w3, posix.fileno(io.stderr))
        posix.close(r1)
        posix.close(w2)
        posix.close(w3)

        local ret, err = posix.execp(path, unpack({...}))
        assert(ret ~= nil, "execp() failed")

        posix._exit(1)
        return
    end

    posix.close(r1)
    posix.close(w2)
    posix.close(w3)

    return pid, w1, r2, r3
end

--
-- Pipe input into cmd + optional arguments and wait for completion
-- and then return status code, stdout and stderr from cmd.
--
function pipe_simple(input, cmd, ...)
    --
    -- Launch child process
    --
    local pid, w, r, e = popen3(cmd, unpack({...}))
    assert(pid ~= nil, "filter() unable to popen3()")

    --
    -- Write to popen3's stdin, important to close it as some (most?) proccess
    -- block until the stdin pipe is closed
    --
    posix.write(w, input)
    posix.close(w)

    local bufsize = 4096
    --
    -- Read popen3's stdout via Posix file handle
    --
    local stdout = {}
    local i = 1
    while true do
        buf = posix.read(r, bufsize)
        if buf == nil or #buf == 0 then break end
        stdout[i] = buf
        i = i + 1
    end

    --
    -- Read popen3's stderr via Posix file handle
    --
    local stderr = {}
    local i = 1
    while true do
        buf = posix.read(e, bufsize)
        if buf == nil or #buf == 0 then break end
        stderr[i] = buf
        i = i + 1
    end

    --
    -- Clean-up child (no zombies) and get return status
    --
    local wait_pid, wait_cause, wait_status = posix.wait(pid)

    return wait_status, table.concat(stdout), table.concat(stderr)
end

--
-- Example usage
--
local my_in = io.stdin:read("*all")
--local my_cmd = "wc"
--local my_args = {"-l"}
local my_cmd = "spamc"
local my_args = {} -- no arguments
local my_status, my_out, my_err = pipe_simple(my_in, my_cmd, unpack(my_args))

-- Obviously not interleaved as they would have been if printed in realtime
io.stdout:write(my_out)
io.stderr:write(my_err)

os.exit(my_status)

Answer 5

以下是我解决问题的方法，需要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

在执行myProgram期间，您将从正常的io读取和写入，在此部分代码之后，您只需要在IN和OUT上进行写入/读取以与子程序进行通信

Answer 6

避免使用临时文件的不太好的解决方案...

require("io")
require("posix")

x="hello\nworld"

posix.setenv("LUA_X",x)
i=popen('echo "$LUA_X" | myfilter')
x=i.read("*a")

Answer 7

这很简单，不需要扩展（使用lua 5.3进行测试）。

#!/usr/bin/lua
-- use always locals
local stdin = io.stdin:lines()
local stdout = io.write

for line in stdin do
    stdout (line)
end

另存为inout.lua并执行chmod +x /tmp/inout.lua

20:30 $ foo=$(echo "bla"|  /tmp/inout.lua)
20:30 $ echo $foo
bla

你如何用lua构建一个读写管道？

7 个答案: