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Better using Crontab

Here are a few tips to get more out of Cron:

• Test your scripts using Cron limited environment
• Have it send you report to another email than root@locahost
• Make it use another shell.

# Cron only provides a limited environment.
# To simulate it to test run your scripts

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CLI: Output the difference between 2 files

Thinking of using diff? Try comm, its sole purpose is to compare 2 sorted files line by line.

Show lines in A.txt but NOT in B.txt:

comm -2 -3 A.txt B.txt

If the files aren’t sorted, use:

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Need to make sense of large CSV files?

Often you are handed-out big CSV files and need to sort, filter, update some cells or other tedious work. You tried sed, jq, and maybe the mighty awk.

But at the end of the day: You’re using the wrong tool for the job.

Here come csvkit’s csvsql, a small Python script to parse your CSV files and create the corresponding database. You now have the best tool, SQL, to answer your data questions:

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3 Python modules you can use directly on the CLI

1. Start a local webserver to serve the file of your current directory on the LAN:

# Python version 2.x:
python -m SimpleHTTPServer 
# Python version 3.x:
python3 -m http.server

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A better setup for Git

Git default configuration is good but it can be personalized to improve your workflow efficiency. Here are some good lines to put in your ~/.gitconfig:

# The basics, who you commit as:
[user]
  name = John Doe
  email = [email protected]

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How to grep search committed code in git?

Search working tree for text matching regular expression regexp:

git grep regexp 

Search working tree for lines of text matching regexp A or B:

git grep -e A --or -e B 

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5 handy JavaScript one-liners

1. Generate a random string:

Math.random().toString(36).substr(2); 

This simply generates a random float, casts it into a String using base 36 and remove the 2 first chars 0 and. Note that this is not a replacement for UUID generation.

2. Clone an array:

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A simple way to benchmark your code in Python

You’re working on your script and want to see how fast a function would be. Here’s how to do that with the timeit module, included in the standard library.

Let’s say you have the following script:

import random

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Proper way to do backup (and restore!) with PostgreSQL 🐘

Postgres provides us several options to do backup just like we want. I’ve tried several strategies in the past, and here is the one I stick to now, for both its simplicity and efficiency.

Backup your database with:

# This is using Postgres custom format
pg_dump -Fc dbname > filename

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Use another mirror when PyPI go down

Find a mirror geographically close to you and use it like this:

pip install -i https://[mirror-url]/simple package

For instance, using a Beijing mirror:

pip install -i https://pypi.douban.com/simple package