Missing.csail.mit.edu

Version Control Systems track changes to a folder and its contents in a series of snapshots. Each snapshot encapsulates the entire state of files/folders within a top-level directory.

Git’s interface is a leaky abstraction. While the interface is at times ugly, its underlying design and ideas are beautiful. A bottom-up explanation of Git therefore makes more sense.

Topic 1: The Shell. missing.csail.mit.edu .

What is the Shell?

At their very core, shells are all roughly the same: they allow you to run programs, give them input, and inspect their output in a semi-structured way.

Potpourri of Shell Utilities and Programs

We can find out which file is executed for a given program name using the which program, e.g. $ which python gives me /Users/dchege711/anaconda3/bin/python

Topic 2: Shell Tools. missing.csail.mit.edu .

Unlike other scripting programming languages, shell scripting is optimized for shell related tasks, e.g. reading from STDIN and saving results into files are primitives.

Pesky Whitespace

foo = bar
# Doesn't work because it's interpreted as calling the foo program with the args '=' and 'bar'
foo=bar # Now that works!

Literal Strings vs. Substitutable Strings

Single quotes are literal strings, but double quotes allow variable substitution.

Debugging 101

printf Debugging and Logging

In printf debugging, one adds print statements and keeps iterating until enough information has been extracted.

Using logging has several advantages over printf debugging: varying logging destinations (e.g. standard output, files, sockets, remote servers, etc.); severity levels (e.g. INFO, DEBUG, WARN, ERROR, &c) that support filtering of output; color-coding for readability.