dockcross/imagefiles
Jean-Christophe Fillion-Robin bd234af0a9
dockcross: Prevent dockcross from blocking when used with Python subprocess
As explained in [1], when using dockcross from python subprocess, the
interactive mode is disabled and output of "cat /dev/urandom" is block
buffered instead of being line buffered.

Workaround to this problem is to simply read a fixed amount of characters
from urandom.

The following two snippets illustrates the problem and the
the implemented  solution:

Works

```python
import subprocess as sp
sp.check_call("var=$(head -c 500 /dev/urandom | base64 | tr -dc 'a-zA-Z0-9' | fold -w 7 | head -n 1); echo $var", shell=True)
```

=> output random string


Fail:

```python
import subprocess as sp
sp.check_call("var=$(cat /dev/urandom | base64 | tr -dc 'a-zA-Z0-9' | fold -w 7 | head -n 1); echo $var", shell=True)
```

=> Hang

[1] http://stackoverflow.com/questions/16805827/unable-to-read-stdout-from-a-running-process#16806506
2016-10-30 03:27:10 -04:00
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