io.popen - how to wait for process to finish in Lua?

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If you are using standard Lua your code looks a bit odd. I am not completely sure about io.popen semantics regarding timeouts or platform dependencies, but the following works at least on my machine.

local file = assert(io.popen('/bin/ls -la', 'r'))
local output = file:read('*all')
file:close()
print(output) -- > Prints the output of the command.
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Chet
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Chet

Updated on July 09, 2022

Comments

  • Chet
    Chet over 1 year

    I have to use io.popen in Lua to run an executable which takes a command line argument. How to wait for a process to finish in the Lua so that expected output can be captured?

      local command = "C:\Program Files\XYZ.exe /all"
    
      hOutput = io.popen(command)
      print(string.format(""%s", hOutput))
    

    Suppose the executable is XYZ.exe which needs to be called with command line argument /all.

    Once io.popen(command) gets executed, the process will return some string which needs to be printed.

    My code snippet:

    function capture(cmd, raw)
      local f = assert(io.popen(cmd, 'r'))
      -- wait(10000); 
      local s = assert(f:read('*a')) 
      Print(string.format("String: %s",s )) 
      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 
    local command = capture("C:\Tester.exe /all")
    

    Your help will be appreciated.

  • rubo77
    rubo77 over 4 years
    can you explain, why you need the assert around?
  • ponzao
    ponzao over 4 years
    @rubo77, I haven't used Lua in a while, but based on a quick test I don't think the assert is at all useful in this case as io.popen seems to return an object even when there is an error.

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