#!/usr/bin/env python
# coding: utf-8

# # Running Scripts from IPython

# IPython has a `%%script` cell magic, which lets you run a cell in
# a subprocess of any interpreter on your system, such as: bash, ruby, perl, zsh, R, etc.
# 
# It can even be a script of your own, which expects input on stdin.

# In[1]:


import sys


# ## Basic usage

# To use it, simply pass a path or shell command to the program you want to run on the `%%script` line,
# and the rest of the cell will be run by that script, and stdout/err from the subprocess are captured and displayed.

# In[2]:


get_ipython().run_cell_magic('script', 'python2', "import sys\nprint 'hello from Python %s' % sys.version\n")


# In[3]:


get_ipython().run_cell_magic('script', 'python3', "import sys\nprint('hello from Python: %s' % sys.version)\n")


# IPython also creates aliases for a few common interpreters, such as bash, ruby, perl, etc.
# 
# These are all equivalent to `%%script <name>`

# In[4]:


get_ipython().run_cell_magic('ruby', '', 'puts "Hello from Ruby #{RUBY_VERSION}"\n')


# In[5]:


get_ipython().run_cell_magic('bash', '', 'echo "hello from $BASH"\n')


# ## Capturing output

# You can also capture stdout/err from these subprocesses into Python variables, instead of letting them go directly to stdout/err

# In[6]:


get_ipython().run_cell_magic('bash', '', 'echo "hi, stdout"\necho "hello, stderr" >&2\n')


# In[7]:


get_ipython().run_cell_magic('bash', '--out output --err error', 'echo "hi, stdout"\necho "hello, stderr" >&2\n')


# In[8]:


print(error)
print(output)


# ## Background Scripts

# These scripts can be run in the background, by adding the `--bg` flag.
# 
# When you do this, output is discarded unless you use the `--out/err`
# flags to store output as above.

# In[9]:


get_ipython().run_cell_magic('ruby', '--bg --out ruby_lines', 'for n in 1...10\n    sleep 1\n    puts "line #{n}"\n    STDOUT.flush\nend\n')


# When you do store output of a background thread, these are the stdout/err *pipes*,
# rather than the text of the output.

# In[10]:


ruby_lines


# In[11]:


print(ruby_lines.read())


# ## Arguments to subcommand

# You can pass arguments the subcommand as well,
# such as  this example instructing Python to use integer division from Python 3:

# In[12]:


get_ipython().run_cell_magic('script', 'python2 -Qnew', 'print 1/3\n')


# You can really specify *any* program for `%%script`,
# for instance here is a 'program' that echos the lines of stdin, with delays between each line.

# In[13]:


get_ipython().run_cell_magic('script', '--bg --out bashout bash -c "while read line; do echo $line; sleep 1; done"', 'line 1\nline 2\nline 3\nline 4\nline 5\n')


# Remember, since the output of a background script is just the stdout pipe,
# you can read it as lines become available:

# In[14]:


import time
tic = time.time()
line = True
while True:
    line = bashout.readline()
    if not line:
        break
    sys.stdout.write("%.1fs: %s" %(time.time()-tic, line))
    sys.stdout.flush()


# ## Configuring the default ScriptMagics

# The list of aliased script magics is configurable.
# 
# The default is to pick from a few common interpreters, and use them if found, but you can specify your own in ipython_config.py:
# 
#     c.ScriptMagics.scripts = ['R', 'pypy', 'myprogram']
# 
# And if any of these programs do not apear on your default PATH, then you would also need to specify their location with:
# 
#     c.ScriptMagics.script_paths = {'myprogram': '/opt/path/to/myprogram'}