hrchu

def gen():
    a = range(5)
    for x in a:
        yield x
        
x = gen() # instanlize

x.__next__() # get next
Out[36]: 0
next(x) # alternative way

hrchu

# replace /sys/class/leds/led0/trigger with /sys/class/leds/led0 while on Raspberry Pi 2 model B


def read_trigger() -> str:
    with open('/sys/class/leds/led0/trigger', 'r') as trigger:
        return trigger.read()

org_trigger = read_trigger()
def disable_trigger():
    with open('/sys/class/leds/led0/trigger', 'w') as trigger:

hrchu

18.04 
apt install python3-pip

16.04
sudo apt-get install vim htop nmon ngrep iftop tmux dnsmasq curl ifstat iperf httpie python-virtualenv build-essential

hrchu

#include <Python.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mtio.h>
#include <stdio.h>
#include <stdlib.h>
#include <linux/input.h>

char* getDeviceName(char* device, char* name, size_t len)

hrchu

TRY IT

0. sudo apt-get install heirloom-mail
1. config your email address and MTA server in send-mail.sh
2. sudo cp send-mail.sh /opt/send-mail.sh
3. sudo cp dummy.* /etc/systemd/system/
4. execute sudo systemctl start dummy.service to confirm it works.
5. sudo systemctl start dummy.timer
6. Check the schedule via systemctl list-timers

hrchu

How to get a stack trace for each thread in a running python script

Sometimes a python script will simply hang forever with no indication of where things went wrong. Perhaps it's polling a service that will never return a value that allows the program to move forward. Here's a way to see where the program is currently stuck.

Install gdb and pyrasite

Install gdb.

# Redhat, CentOS, etc

hrchu

alist = [[1,1],[1,1]]

assert([1, 1] == [x for x, y in alist]) # OK

for x, y in alist: # OK
  assert x == 1

assert([1, 1] == list(map(lambda x, y: x, alist))) # TypeError: <lambda>() missing 1 required positional argument: 'y'

hrchu

Setting up ssh public key authentication on macOS using a YubiKey 4

I largely followed Florin's blog post, but have a few notes to add regarding issues I encountered:

Basic setup notes

1. I used a YubiKey 4, while the blog describes using a YubiKey NEO. I'm sure a YubiKey 5 would also work. I'm also running macOS 10.13.6.
2. I installed GPGTools as recommended. However, as I'll note later, it seems that gpg-agent only automatically starts when gpg is used; for ssh, you'll need to ensure it's running.
3. Before generating your keys, decide what key size you want to use. If you run the list command inside gpg --edit-card, look for the Key attributes line to see what is currently selected. On my YubiKey 4, it defaulted to 2048 bits for all keys:

Key attributes ...: rsa2048 rsa2048 rsa2048

hrchu

# install phantomjs on ubuntu 16.04.4
wget https://bitbucket.org/ariya/phantomjs/downloads/phantomjs-2.1.1-linux-x86_64.tar.bz2
tar xvjf phantomjs-2.1.1-linux-x86_64.tar.bz2
sudo cp phantomjs-2.1.1-linux-x86_64/bin/phantomjs /usr/bin/
phantomjs --version
sudo cp phantomjs-2.1.1-linux-x86_64/bin/phantomjs /usr/local/bin/

hrchu

curl -fsSL https://get.docker.com -o get-docker.sh
sudo sh get-docker.sh
sudo curl -L "https://github.com/docker/compose/releases/download/1.24.0/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose