Things I learned/revisited this week#1

Reading SSL certificate material with python cryptography library…deleting git branches…docker command formatting…escaping liquid syntax in markdown.

• Load x509 certificate and rsa key files using Python cryptography library

from cryptography as x509
with open(cert_file, "rb") as cert_file_fp:
    # opening the file in byte mode
    cert_file_pem = x509.load_pem_x509_certificate(cert_file_fp.read())
    print(cert_file_pem.serial_number, cert_file_pem.subject)
    # backend parameter deprecated from version 36.0.0 onwards
    # See https://cryptography.io/en/latest/faq/#what-happened-to-the-backend-argument
    # cert_file_pem = x509.load_pem_x509_certificate(cert_file_fp.read(), backend=default_backend())

from cryptography.hazmat.primitives import serialization
with open(key_file, "rb") as key_file_fp:
    # unencrypted key, so leaving the password as None
    key_file_pem = serialization.load_pem_private_key(
                                    key_file_fp.read(), 
                                    password=None)
    # dumping the public key info
    public_key = key_file_pem.public_key()
    print(public_key.public_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PublicFormat.SubjectPublicKeyInfo
    ))                                 

• Deleting local and remote branches in Git.
  1. local
     1. to delete => git branch --delete <branch-name> (or git branch -d)
     2. to force delete => git branch --delete --force <branch-name> (or git branch -D <branch-name>)
  2. remote - git push origin --delete <remote-branch-name>

• perror(“some msg”) from standard library - prints some msg: <description of error matching errno>. (use strerror(errno) to get just the description of errno)

• Format docker images output to display only the image and tag information => $(docker images --format '{{.Repository}}:{{.Tag}}'). Formatting is based on Go templates. This is often useful in scripting to use only the needed fields.

$ docker images
REPOSITORY   TAG       IMAGE ID       CREATED       SIZE
nginx        latest    7425d3a7c478   3 weeks ago   142MB

$ # {{..}} are the Actions
$ # all text between actions is copied verbatim 
$ docker images --format '{{.Repository}}:{{.Tag}}'
nginx:latest

• Escape liquid syntax in markdown with {% raw %} and {% endraw %} tags. Thanks to this post. The second workaround of using jekyll variables was helpful to even escape raw and endraw tags.