feat: update lesson 2 and add appendix entry

appendix.md

@@ -45,3 +45,25 @@ A mapping of qsv release files for an arbitrary version X.Y.Z and platforms they
 :::{note}
 The listed OS/architecture are primarily based on [information from "The rustc book"](https://doc.rust-lang.org/nightly/rustc/platform-support.html).
 :::
+
+(command-data-streams)=
+## Command data streams (`stdin`, `stdout`, and `stderr`)
+
+The terms `stdin`, `stdout`, and `stderr` may commonly be found within qsv's source code and in the lessons.
+
+Here's a very brief explanation of what each means in the context of a command:
+
+- `stdin` ("Standard input"): Input data
+- `stdout` ("Standard out"): Output data
+- `stderr` ("Standard error"): Error output
+
+Let's consider the following pipeline as an example:
+
+```bash
+qsv clipboard | qsv stats -E
+```
+
+- There are two commands ran here, each separated by a pipe (`|`).
+- The output (`stdout`) of `qsv clipboard` is used as the input (`stdin`) of `qsv stats -E`.
+
+For further explanation you may read online articles regarding piping commands. You may view a few more examples [here](https://zerotomastery.io/cheatsheets/linux-commands-cheat-sheet/#piping-and-command-redirection).

lessons/2/exercise.ipynb

@@ -0,0 +1,52 @@
+{
+    "cells": [
+        {
+            "cell_type": "markdown",
+            "metadata": {},
+            "source": [
+                "# Exercise 2: Piping commands\n",
+                "\n",
+                "Pipe the first and second columns of `fruits_extended.csv` into `qsv table`."
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": null,
+            "metadata": {},
+            "outputs": [],
+            "source": [
+                "qsv select --help"
+            ]
+        },
+        {
+            "cell_type": "markdown",
+            "metadata": {},
+            "source": [
+                "After running that pipeline and viewing the output, try adding `qsv transpose` before `qsv table` in the pipeline and see what the output looks like."
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": null,
+            "metadata": {
+                "vscode": {
+                    "languageId": "plaintext"
+                }
+            },
+            "outputs": [],
+            "source": []
+        }
+    ],
+    "metadata": {
+        "kernelspec": {
+            "display_name": "Bash",
+            "language": "bash",
+            "name": "bash"
+        },
+        "language_info": {
+            "name": "bash"
+        }
+    },
+    "nbformat": 4,
+    "nbformat_minor": 2
+}

lessons/2/index.md

@@ -11,13 +11,6 @@ kernelspec:
 
 # Lesson 2: Piping commands
 
-:::{admonition} Lesson is a work in progress
-:class: warning
-
-This lesson is not complete. Stay tuned!
-
-:::
-
 We've been using one command at a time, but what if we want to use multiple?
 
 For example let's say I want to only see what fruits there are and their availability from `fruits_extended.csv` in a nicely formatted table.
@@ -49,7 +42,7 @@ Great, we got the column data that we're looking for. But how do we run this dat
 
 ## Command redirection
 
-If you're not sure what `stdin`, `stdout`, and `stderr` are then we recommend reading the "Command data streams (`stdin`, `stdout`, and `stderr`)" section in the Appendix.
+If you're not sure what `stdin`, `stdout`, and `stderr` are then we recommend reading the [Command data streams](command-data-streams) section in the Appendix.
 
 <!-- Add link to appendix or do a dropdown or continue lesson and explain each one. -->
 <!-- Improve flow for previous sentence to next one or modify flow. -->
@@ -63,9 +56,59 @@ qsv select 1,4 fruits_extended.csv | qsv table
 
 Now we've got what we were looking for!
 
-:::{admonition} Exercise is a work in progress
+Notice that the output of the first command `qsv select 1,4 fruits_extended.csv` was used as the input for `qsv table`.
-:class: important
 
-The exercise for this lesson is not available yet. Stay tuned!
 
-:::
+## Exercise 2: Piping commands example
+
+[![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/dathere/100.dathere.com/main?labpath=lessons%2F2%2Fexercise.ipynb)
+
+Pipe the first and second columns of `fruits_extended.csv` into `qsv table`.
+
+After running that pipeline and viewing the output, try adding `qsv transpose` before `qsv table` in the pipeline and see what the output looks like.
+
+> Here we show the usage text of `qsv select` for your reference. Solve this exercise using [Thebe](exercises-setup:thebe), [Binder](exercises-setup:binder) or [locally](exercises-setup:local).
+
+```{code-cell}
+:tags: ["scroll-output"]
+qsv select --help
+```
+
+::::{admonition} Solution
+:class: dropdown seealso
+
+For the first part, you may run:
+
+```bash
+qsv select 1,2 fruits_extended.csv | qsv table
+```
+
+The output should be:
+
+```
+fruit       size
+apple       medium
+banana      medium
+strawberry  small
+orange      medium
+pineapple   large
+grape       small
+mango       medium
+watermelon  large
+pear        medium
+```
+
+The second part is adding `qsv transpose` within the pipeline:
+
+```bash
+qsv select 1,2 fruits_extended.csv | qsv transpose | qsv table
+```
+
+The output should be:
+
+```
+fruit  apple   banana  strawberry  orange  pineapple  grape  mango   watermelon  pear
+size   medium  medium  small       medium  large      small  medium  large       medium
+```
+
+::::