Merge branch 'master' into vhs

basics/cron.md

@@ -14,20 +14,31 @@ Once installed, search for the service name, and start it.
 
 ```bash
 sudo systemctl list-unit-files | grep cron
+sudo systemctl enable --now $NAME
 ```
 
+Make a file for your crontab, like this:
+
 ```bash
-sudo systemctl enable --now cron
+echo '39 */3 * * * /usr/bin/updatedb' > "$USER".cron
 ```
 
-You can *e*dit your crontab with:
+Then apply that crontab:
 
 ```bash
-crontab -e
+crontab "$USER".cron
+rm "$USER".cron
 ```
+The `cron` program will check your syntax before adding the tab.
 
+Your crontab file sits somewhere in `/var/spool/`.
+Probably in `/var/spool/cron`.
 
-> 39 */3 * * * /usr/bin/updatedb
+Check how your tab currently looks:
+
+```bash
+crontab -l
+```
 
 ## Syntax
 
@@ -91,7 +102,7 @@ run-parts /etc/cron.hourly
 ### Variables
 
 Add your `$HOME` to crontab to use scripts.
-First add `HOME=/home/user`, then you can use syntax like this:
+First add `HOME=/home/$USER`, then you can use syntax like this:
 
 0 * * * * $HOME/.scripts/myScript.sh
 
@@ -100,7 +111,6 @@ First add `HOME=/home/user`, then you can use syntax like this:
 ```bash
 $HOME/.scripts/myScript.sh
 ```
-
 You can also add your regular path to your crontab as a variable (see example below).
 If you're using vim as the editor, just run this at the top of your crontab:
 
@@ -131,5 +141,3 @@ PATH=/usr/condabin:/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/bin/site_perl:/u
 50 18 * * * /usr/bin/timeout 30m /usr/bin/syncthing
 
 ```
-
-

basics/eval.md

@@ -0,0 +1,22 @@
+---
+title: "eval"
+tags: [ "basics" ]
+---
+
+Compose a statement for execution.
+
+```bash
+x='echo $y'
+echo $x
+y=dragon
+eval "$x"
+```
+
+The results remain in the current shell, unlike sub-shells.
+
+```bash
+b=basilisk
+sh -c 'echo $b'
+eval "g=goblin"
+echo $g
+```

basics/games.md

@@ -0,0 +1,11 @@
+---
+title: "bash games"
+tags: [ "Documentation", "Games" ]
+---
+
+Games are a great way to learn bash.
+
+- `mapscii.me` is an interactive terminal map.
+    1. Install telnet.
+    1. `telnet mapscii.me`
+- [Over the Wire](https://overthewire.org/wargames) teaches bash with small challenging you can do over `ssh`.

basics/tree.md

@@ -1,6 +1,6 @@
 ---
 title: "tree"
-tags: [ "basics" ]
+tags: [ "basics", "tree", "markdown" ]
 ---
 
 The `tree` utility outputs a full listing of everything in your current directory, and those below.
@@ -23,3 +23,14 @@ README.md
 ```
 
 Each description-line starts with a tab.
+
+## Markdown Conversion
+
+To represent a file structure as a nested series of markdown lists, you can try this horrifying `sed` one-liner:
+
+```bash
+tree -tf --dirsfirst --gitignore --noreport --charset ascii  | \
+    sed -e 's/| \+/  /g' \
+    -e 's/[|`]-\+/ */g' \
+    -e 's:\(* \)\(\(.*/\)\([^/]\+\)\):\1[\4](\2):g'
+```