Creating a Terminal Program with Python

On a *nix system (linux/unix),
if you:

$ chmod 0744 your_file.py

-rwxr--r--   your_file.py

and add the path to python as the first line of your_file.py:

#!/usr/bin/python

or (in my case):

#!/usr/local/bin/python

Once you do that, instead of running it like this:

$ python your_file.py

You can run it like this:

$ ./your_file.py

or even rename it to yourfile and run it like this:

$ ./yourfile

and if you then copy yourfile to your bin (i.e. #!/usr/bin/, or #!/usr/local/bin/)
you can run it like this:

$ yourfile

Then you can…

Use raw_input() to solicit and get input from you user.

your_file.py:

#!/usr/local/bin/python

import os

while(True):
    # cntrl-c to quit
    input = raw_input('your_prompt$ ')
    input = input.split()
    if input[0] == 'ls':
        dire="."
        if len(input) > 1:
            dire = input[1]
        print('\n'.join(os.listdir(dire)))
    else:
        print('error')

your_file.py use example:

$ chmod 744 your_file.py 
$ cp your_file.py /usr/local/bin/your_file 
$ your_file 
your_prompt$ ls
list_argv.py
your_file.py
your_ls.py
your_subprocess.py
your_prompt$ ls .
list_argv.py
your_file.py
your_ls.py
your_subprocess.py
your_prompt$ pwd
error
your_prompt$ ^CTraceback (most recent call last):
  File "/usr/local/bin/your_file", line 7, in <module>
    input = raw_input('your_prompt$ ')
KeyboardInterrupt
$

Grab arguments with sys.argv from the command line when you run your script:

list_argv.py:

#!/usr/local/bin/python

import sys

print(sys.argv)

list_argv.py use example:

$ python list_argv.py 
['list_argv.py']
$ python list_argv.py hello
['list_argv.py', 'hello']
$ python list_argv.py hey yo
['list_argv.py', 'hey', 'yo']

$ chmod 744 list_argv.py 
$ ./list_argv.py 
['./list_argv.py']
$ ./list_argv.py hi
['./list_argv.py', 'hi']
$ ./list_argv.py hey yo
['./list_argv.py', 'hey', 'yo']

$ cp list_argv.py /usr/local/bin/list_argv
$ list_argv hey yo
['/usr/local/bin/list_argv', 'hey', 'yo']

Replace raw_input() with sys.argv.

‘your_ls.py’:

#!/usr/local/bin/python

import sys
import os

dire="."
if len(sys.argv) > 1:
    dire = sys.argv[1]
print('\n'.join(os.listdir(dire)))

‘your_ls.py’ use example:

$ chmod 744 your_ls.py 
$ cp your_ls.py /usr/local/bin/your_ls
$ your_ls 
list_argv.py
your_file.py
your_ls.py
your_subprocess.py
$ your_ls .
list_argv.py
your_file.py
your_ls.py
your_subprocess.py
$ your_ls blah
Traceback (most recent call last):
  File "/usr/local/bin/your_ls", line 9, in <module>
    print('\n'.join(os.listdir(dire)))
OSError: [Errno 2] No such file or directory: 'blah'

Use subprocess.Popen to access anything you could from the command line.

your_subprocess.py:

#!/usr/local/bin/python

import os
import subprocess

while(True):
    # cntrl-c to quit
    input = raw_input('your_prompt$ ')

    process = subprocess.Popen(input, shell=True,
                           stdout=subprocess.PIPE,
                           stderr=subprocess.PIPE)

    out, err = process.communicate()

    print(out)
    print(err)

your_subprocess.py use example:

$ chmod 744 your_subprocess.py 
$ cp your_subprocess.py /usr/local/bin/your_subprocess
$ your_subprocess 
your_prompt$ ls
list_argv.py
your_file.py
your_ls.py
your_subprocess.py


your_prompt$ ls .
list_argv.py
your_file.py
your_ls.py
your_subprocess.py


your_prompt$ pwd
/Users/ox/_workspace/cmd_ln


your_prompt$ blah

/bin/sh: blah: command not found

your_prompt$ ^CTraceback (most recent call last):
  File "/usr/local/bin/your_subprocess", line 8, in <module>
    input = raw_input('your_prompt$ ')
KeyboardInterrupt
$

BREAK STUFF!

😀

HAVE FUN!

-ox