In Git you can add a submodule to a repository. This is basically a repository embedded in your main repository. This can be very useful. A couple of usecases of submodules:
- Separate big codebases into multiple repositories.
Latency Comparison Numbers (~2012) | |
---------------------------------- | |
L1 cache reference 0.5 ns | |
Branch mispredict 5 ns | |
L2 cache reference 7 ns 14x L1 cache | |
Mutex lock/unlock 25 ns | |
Main memory reference 100 ns 20x L2 cache, 200x L1 cache | |
Compress 1K bytes with Zippy 3,000 ns 3 us | |
Send 1K bytes over 1 Gbps network 10,000 ns 10 us | |
Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD |
Magic words:
psql -U postgres
Some interesting flags (to see all, use -h
or --help
depending on your psql version):
-E
: will describe the underlaying queries of the \
commands (cool for learning!)-l
: psql will list all databases and then exit (useful if the user you connect with doesn't has a default database, like at AWS RDS)# Add the following 'help' target to your Makefile | |
# And add help text after each target name starting with '\#\#' | |
help: ## Show this help. | |
@fgrep -h "##" $(MAKEFILE_LIST) | fgrep -v fgrep | sed -e 's/\\$$//' | sed -e 's/##//' | |
# Everything below is an example | |
target00: ## This message will show up when typing 'make help' | |
@echo does nothing |
#!/usr/bin/env python | |
""" | |
Very simple HTTP server in python (Updated for Python 3.7) | |
Usage: | |
./dummy-web-server.py -h | |
./dummy-web-server.py -l localhost -p 8000 | |
Send a GET request: |
# one or the other, NOT both | |
[url "https://github"] | |
insteadOf = git://github | |
# or | |
[url "git@github.com:"] | |
insteadOf = git://github |