[erlang-questions] Running multiple commands like os:cmd/1

Attila Rajmund Nohl <>
Mon Dec 31 15:32:23 CET 2012


In this case you might want to put this "sequence of command" into a
shell script (because they are essentially that) and execute the
script. Use if, while, for, etc. in the script for controlling the
execution.

2012/12/31 Gleb Peregud <>:
> This would work, but since sometimes sequence of commands can change
> depending on results of other commands in the sequence it does not fit
> my case.
>
> On Fri, Dec 28, 2012 at 6:44 AM, Garrett Smith <> wrote:
>> Have you experimented with calling the shell as a single command, passing
>> along the string to execute? E.g.
>>
>> bash -c "<your series of commands>"
>>
>> Garrett
>>
>> On Dec 26, 2012 2:37 PM, "Gleb Peregud" <> wrote:
>>>
>>> Happy holidays, everyone!
>>>
>>> I want to run multiple commands in a single shell from my code through
>>> some sort of open_port({spawn, ...}). I have four requirements:
>>> 1) I want it to work asynchronously (i.e. I start a command and I get
>>> it's results streamed to a process as it happens);
>>> 2) I want to know exactly when a command finishes;
>>> 3) Binary output should be handled properly;
>>> 4) Changes in env variables should be preserved between commands.
>>>
>>> A naive sequence of os:cmd/1 or open_port({spawn, ...}) doesn't
>>> satisfy requirement 4.
>>>
>>> os:cmd/1 has a nice backend code in there, but it doesn't satisfy
>>> requirement 3. It has a bug. Try running length(os:cmd("head -c 1000
>>> /dev/urandom")).
>>>
>>> open_port({spawn, "/bin/sh -s -"}, [line]) with port_command/2 doesn't
>>> satisfy requirement 2.
>>>
>>> Any ideas how to implement it? Is there any library which does it?
>>>
>>> Cheers,
>>> Gleb
>>> _______________________________________________
>>> erlang-questions mailing list
>>> 
>>> http://erlang.org/mailman/listinfo/erlang-questions
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