december 2021 – Roholt

Restore a deleted file in git

29 december 2021 / Mr R. / Geen reacties

Git is your lifesaver if you have deleted a file somewhere in the past and committed that change.

Due to the nature of Git that file is not gone, but just hidden.
You can retrieve that file by using “checkout”.

You should select the commit before the file got deleted or you’ll see an:

error: pathspec '<your-file-to-retrieve>' did not match any file(s) known to git.

So, suppose your commit is at 48b8bc and you want to retrieve some-file.txt:

git checkout 48b8bc -- some-file.txt

Now the file you were looking for should be in your new files when checking it with: “git status”.

Ping addresses on a subnet (no nmap)

27 december 2021 / Mr R. / Geen reacties

If you are on a remote host, and you have not the rights to install any other software, then this might come in handy.

Normally I would use “nmap” to scan for other devices on the network, but if that is not available and “ping” is, then this can also discover online devices on the network, assuming they are pingable (ICMP enabled).

#!/bin/bash
# Ping devices on a subnet

SUBNET=${1:-"192.168.2"}

function main()
{
  for i in $SUBNET.{1..254}
  do
    check_alive $i &
  done

  # Sleep to not put shell inbetween
  sleep 1
  exit 0
}

function check_alive()
{
  ping -c 1 $1 > /dev/null
  [ $? -eq 0 ] && echo -e "$i\t UP"
}

main $@

The output will look like the following:

⇒  ./ping-it.sh 192.168.2
192.168.2.69	 UP
192.168.2.62	 UP
192.168.2.254	 UP
192.168.2.14	 UP
192.168.2.65	 UP
192.168.2.182	 UP
192.168.2.25	 UP
192.168.2.200	 UP
192.168.2.210	 UP
192.168.2.190	 UP

Meaning of “man” numbers (e.g. mkfifo(3)

27 december 2021 / Mr R. / Geen reacties

I always forget what the number after the man pages means.
For example mkfifo(3) (https://linux.die.net/man/3/mkfifo).

This post helps me (and you) to not forget 🙂

MANUAL SECTIONS
    The standard sections of the manual include:

    1      User Commands
    2      System Calls
    3      C Library Functions
    4      Devices and Special Files
    5      File Formats and Conventions
    6      Games et. al.
    7      Miscellanea
    8      System Administration tools and Daemons

    Distributions customize the manual section to their specifics,
    which often include additional sections.

Note: I found out that “man” has a man page of itself. So this is not really necessary anymore. I keep it here for others to find though.

But remember:

$ man man

Python3 custom logging module

7 december 2021 / Mr R. / Geen reacties

I made a logging module based on the logging module of python itself.

It prints to file, and also in the console, and rotates the file automatically on a new start.

# Use it in your other modules as:
  # from Log import Log
  # logger = Log(__name__)

import logging
from logging import handlers
import os

LOG_LEVEL = logging.DEBUG

logger = logging.getLogger()
logger.setLevel(LOG_LEVEL)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')

ch = logging.StreamHandler()
ch.setLevel(LOG_LEVEL)
ch.setFormatter(formatter)
logger.addHandler(ch)

filename = "./log/log.txt"
should_roll_over = os.path.isfile(filename)
rfh = handlers.RotatingFileHandler(filename, maxBytes=5 * 1000 * 1000, backupCount=20)
if should_roll_over:
  rfh.doRollover()
rfh.setLevel(LOG_LEVEL)
rfh.setFormatter(formatter)
logger.addHandler(rfh)


class Log():
  def __init__(self, name):
    self.logger = logging.getLogger(name)

    self.info(f"Instantiated logger for {name}")

  def critical(self, msg):
    self.logger.critical(msg)

  def fatal(self, msg):
    self.logger.fatal(msg)

  def error(self, msg):
    self.logger.error(msg)

  def warning(self, msg):
    self.logger.warning(msg)

  def warn(self, msg):
    self.logger.warn(msg)

  def info(self, msg):
    self.logger.info(msg)

  def debug(self, msg):
    self.logger.debug(msg)

Roholt

My Sketchbook!

Tags

Categorieën

Recente berichten

Archieven

Monthdecember 2021

Restore a deleted file in git

Ping addresses on a subnet (no nmap)

Meaning of “man” numbers (e.g. mkfifo(3)

Python3 custom logging module

Recente berichten

Recente berichten