Re: io.popen of unknown program succeeds

[Philipp Janda <siffiejoe@...>]

Am 27.12.2013 22:58 schröbte Rob Kendrick:
> On Fri, Dec 27, 2013 at 04:42:55PM -0500, Sean Conner wrote:
> > > Am I missing something?
> >
> >    It's Linux.
>
> s/Linux/UNIX/
>
> popen() passes the string you give it to the shell (most likely as set
> in $SHELL in the environment);

or just `/bin/sh -c`.

> it has no way of knowing if the arbitrary
> line of shellscript you gave it was successful in running a program or
> not.

But you can find out (in Lua 5.2) by calling the `close` method on the 
returned file pointer:

    > print( io.popen( "no_such_program" ):close() )
    sh: 1: no_such_program: not found
    nil     exit    127
    > print( io.popen( "false" ):close() )
    nil     exit    1
    > print( io.popen( "true" ):close() )
    true    exit    0

> If you want reliability, you need a proper subprocess module that uses
> fork/exec and executes the program directly.
>
> B.

Philipp