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
where RAND is a 7 characters long randomly generated alphanumeric string.
Note that container name can NOT start with "_",
only [a-zA-Z0-9][a-zA-Z0-9_.-] are allowed
See #50
This will allow build script like "build-wheels.sh" to run command like
the following (see [1]):
sudo yum install -y atlas-devel
It will also allow to pip install using sudo and avoid error reported in [3].
That said, instead of running pip using sudo, the recommended approach
is to specify the "--user" flag [2]
[1] 893d92517e/travis/build-wheels.sh
[2] http://stackoverflow.com/questions/7143077/how-can-i-install-packages-in-my-home-folder-with-pip#7143496
[3] Error reported when running pip without "sudo pip install <packagename" or "pip install --user <packagename>"
```
Exception:
Traceback (most recent call last):
File "/opt/_internal/cpython-2.7.11-ucs2/lib/python2.7/site-packages/pip/basecommand.py", line 215, in main
status = self.run(options, args)
File "/opt/_internal/cpython-2.7.11-ucs2/lib/python2.7/site-packages/pip/commands/install.py", line 317, in run
prefix=options.prefix_path,
File "/opt/_internal/cpython-2.7.11-ucs2/lib/python2.7/site-packages/pip/req/req_set.py", line 736, in install
requirement.uninstall(auto_confirm=True)
File "/opt/_internal/cpython-2.7.11-ucs2/lib/python2.7/site-packages/pip/req/req_install.py", line 742, in uninstall
paths_to_remove.remove(auto_confirm)
File "/opt/_internal/cpython-2.7.11-ucs2/lib/python2.7/site-packages/pip/req/req_uninstall.py", line 115, in remove
renames(path, new_path)
File "/opt/_internal/cpython-2.7.11-ucs2/lib/python2.7/site-packages/pip/utils/__init__.py", line 267, in renames
shutil.move(old, new)
File "/opt/_internal/cpython-2.7.11-ucs2/lib/python2.7/shutil.py", line 303, in move
os.unlink(src)
OSError: [Errno 13] Permission denied: '/opt/_internal/cpython-2.7.11-ucs2/bin/easy_install'
```
By default the toolchain file is always passed as an option to cmake/ccmake
It can be explicitly disabled setting the environment variable
DOCKCROSS_PASS_CMAKE_TOOLCHAIN_FILE to 0
