BashLinuxmacOSWSLFoundational~4h

Linux & Shell

Drive the machine from a prompt

A shell is not a worse window manager — it is a small language for pointing programs at files. This is the whole of the interactive half: resolving a path, setting a mode, sending each of the two output streams where you meant it, cutting a file down to an answer, and chaining commands on their verdicts.

Start this projectSee the modules
Modules
5
Drills
1
Build steps
5
Time
~4h

Walk out able to

Answer a real question about a real file with one line you wrote yourself — and know which of the two streams the errors went down.

What you work on

01

Paths and expansion

Resolve any path; predict what a glob hands over.

02

Modes and who gets in

Read `ls -l` at a glance; set 754 without guessing.

03

Two streams and a pipe

Redirection, and why the order of 2>&1 decides it.

04

Text tools and control

grep, sed, awk; exit status, quoting, and jobs.

The pitch

What you practise, and what you leave with

One line, written from a specification rather than a walkthrough, that answers a question about a log you built — plus the number it printed.

You will practise

  • Paths, globs, links and finding things
  • Modes, chmod, and who may do what
  • Redirection, pipes, grep, sed and awk
  • Exit status, quoting and job control

Afterwards you can

  • Resolve any path without writing it down
  • Set a mode from memory, either direction
  • Order 2>&1 correctly, and know why
  • Compose four tools into one pipeline

Modules

5 modules, 28 items

Lessons explain one idea. Drills repeat it until it sticks. Build steps make something that exists afterwards.

  1. 1

    Find your way around

    ~52 min

    Turn any path into the one place it names, and find a file you cannot see.

    • LessonWhy drive a machine from a prompt4 min
    • Build stepBuild a tree of your own to ruin6 min
    • LessonRead a path to the one place it names9 min
    • LessonWhy a relative path is a bug report7 min
    • LessonLet the shell pick the files9 min
    • LessonReach for find when a glob cannot6 min
    • Build stepGive one file two names11 min
  2. 2

    Read and set a mode

    ~47 min

    Read `ls -l` at a glance, and set a mode with chmod without guessing.

    • LessonRead the ten characters at the front7 min
    • LessonTranslate a mode, either direction10 min
    • LessonDelete a file you cannot read9 min
    • LessonChoose a mode from a requirement9 min
    • Build stepMake a script runnable, then undo it12 min
  3. 3

    Wire the two streams

    ~46 min

    Send each stream where you meant it, and know why the order of `2>&1` decides it.

    • LessonTwo streams arriving on one screen8 min
    • LessonWrite 2>&1 in the order you meant10 min
    • LessonWhat travels down a pipe7 min
    • LessonWork a pipeline out stage by stage9 min
    • Build stepSplit the streams, then swap the order12 min
  4. 4

    Cut the file down to the answer

    ~33 min

    Pull the lines and the fields you need with grep, sed and awk.

    • LessonSelect the lines you actually meant8 min
    • LessonKnow which dialect you are in9 min
    • LessonSubstitute, and print everything8 min
    • LessonTake a column out of every line8 min
  5. 5

    Make the shell obey

    ~1h

    Chain commands on their verdicts, quote what you mean, and write the one-liner.

    • LessonRead the verdict, not the message7 min
    • LessonChain commands on their verdicts9 min
    • LessonSay exactly what you meant9 min
    • LessonWhat a program you start inherits7 min
    • LessonPut a job aside and pick it up again12 min
    • DrillFind the line that does not mean it8 min
    • Build stepAnswer a question with one line18 min

A taste of the code

one line, two streams
# notes.md is there; missing.md is not
ls notes.md missing.md > found.txt 2>&1

$ cat found.txt

ls: cannot access 'missing.md': No such file or directory
notes.md

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