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Miscellaneous projects

Running shell commands in python​

Single line shell commands examples:

import subprocess

# example 1
subprocess.run("echo 'hello'", shell=True, check=True, text=True)

# example 2
subprocess.run('cd /tmp; pwd', shell=True)

# example 3
input_text = "Welcome guest"
message = subprocess.run(["echo", input_text], text=True, \
    capture_output=True)
print(message.stdout)

Multiline example:

cmd = '''cd /tmp;
pwd;
'''

subprocess.run(cmd, shell=True, check=True, text=True, \
    universal_newlines=True, executable='/bin/bash')

A more comprehensive example: Encrypt a folder recursively using openssl.

src/encrypt_folder_openssl.py
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Program: Encrypt folder recursively using openssl
Version: 20220105
@author: Pranab Das (GitHub: @pranabdas)
Run: python3 filename.py
"""
import os
import subprocess
import getpass

# ask folder to encrypt
path = input("Please enter the directory/path to encrypt: ")

# Remove any trailing '/'
if (path[-1] == "/"):
    path = path[:-1]

# Get absolute path in case relative path is entered
path = os.path.abspath(path)

# New directory name
new_path = path + "_enc"

# check openssl is installed
try:
    openssl_version = subprocess.run(["openssl", "version"],
                                     text=True, capture_output=True)
except:
    print("openssl not found. Exiting ...")
    exit()

# ask and confirm password
passwd = getpass.getpass(prompt="Please enter encryption password: ")
passwd_confirm = getpass.getpass(prompt="Please confirm your password: ")

if (passwd == passwd_confirm):
    pass
else:
    print("Password mismatch! Exiting ...")
    exit()

print("\nPlease wait. Encrypting...")

for root, dirs, files in os.walk(path):

    # Create the folder structure
    if path in root:
        try:
            os.mkdir(root.replace(path, new_path))
        except FileExistsError:
            pass

    # encrypt files using openssl
    if (files != []):
        for file in files:
            file_path = root + "/" + file
            new_file_path = file_path.replace(path, new_path) + ".enc"

            cmd = f'''openssl enc -e -aes-256-cbc \
                      -salt \
                      -iter 1000000 \
                      -md sha512 \
                      -k {passwd} \
                      -in {file_path} \
                      -out {new_file_path}
                   '''
            subprocess.run(cmd, shell=True, check=True, text=True,
                           universal_newlines=True, executable="/bin/bash")

print("\nDone. Encrypted files are placed under:\n", new_path)
tip

Conversely, you can also include python code in shell script.

Jupyter notebooks of various python projects​