chore: imported knowledge from https://betterprogramming.pub/6-more-terminal-commands-you-should-know-3606cecdf8b6

knowledge base/cmp.md

@@ -0,0 +1,44 @@
+# `cmp`
+
+Compares two files byte by byte.
+
+Prints the line and the character number where the two files diverge.
+
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
+## TL;DR
+
+```sh
+# Print only lines present in both file1 and file2.
+cmp 'path/to/file1' 'path/to/file2'
+```
+
+## Further readings
+
+- [`comm`][comm]
+- [man page]
+
+## Sources
+
+All the references in the [further readings] section, plus the following:
+
+- [6 more terminal commands you should know]
+
+<!--
+  references
+  -->
+
+<!-- project -->
+<!-- article sections -->
+[further readings]: #further-readings
+
+<!-- knowledge base -->
+[comm]: comm.md
+
+<!-- others -->
+[6 more terminal commands you should know]: https://betterprogramming.pub/6-more-terminal-commands-you-should-know-3606cecdf8b6
+[man page]: https://linux.die.net/man/1/cmp

knowledge base/comm.md

@@ -1,19 +1,60 @@
-# comm
+# `comm`
 
-`comm` requires the files it is working with to be pre-sorted.
+Compares two files line by line.
+
+With no options, produces 3 columns in output:
+
+- column 1 contains lines **unique to file 1**;
+- column 2 contains lines **unique to file 2**;
+- column 3 contains lines **common** to both files.
+
+Comparisons honor the rules specified by 'LC_COLLATE'.
+
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
 
 ## TL;DR
 
 ```sh
+# Print only lines present in both file1 and file2.
+comm -12 'path/to/pre-sorted/file1' 'path/to/pre-sorted/file2'
+
 # Print unique lines of file1 which are not present in file2.
-comm -23 <(sort -u 'file1') <(sort -u 'file2')
+comm -23 'path/to/pre-sorted/file1' 'path/to/pre-sorted/file2'
+comm -23 <(sort -u 'path/to/file1') <(sort -u 'path/to/file2')
 
 # Check the whole content of file1 is present in file2.
-[[ $(comm -23 <(sort -u 'file1') <(sort -u 'file2') | wc -l) -eq 0 ]]
+test $(comm -23 'path/to/pre-sorted/file1' <(sort -u 'path/to/file2') | wc -l) -eq 0
+[[ $(comm -23 <(sort -u 'path/to/file1') 'path/to/pre-sorted/file2' | wc -l) -eq 0 ]]
 ```
 
+## Further readings
+
+- [`cmp`][cmp]
+- [man page]
+
 ## Sources
 
-- [Check whether all lines of file occur in different file]
+All the references in the [further readings] section, plus the following:
 
+- [Check whether all lines of file occur in different file]
+- [6 more terminal commands you should know]
+
+<!--
+  references
+  -->
+
+<!-- project -->
+<!-- article sections -->
+[further readings]: #further-readings
+
+<!-- knowledge base -->
+[cmp]: cmp.md
+
+<!-- others -->
+[6 more terminal commands you should know]: https://betterprogramming.pub/6-more-terminal-commands-you-should-know-3606cecdf8b6
 [check whether all lines of file occur in different file]: https://unix.stackexchange.com/questions/397747/check-whether-all-lines-of-file-occur-in-different-file#397749
+[man page]: https://linux.die.net/man/1/comm

knowledge base/iptab.md

@@ -0,0 +1,37 @@
+# `iptab`
+
+Displays a reference table of subnet masks and other IP address space details.
+
+It has no arguments. That's it.
+
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
+## TL;DR
+
+```sh
+iptab
+```
+
+## Further readings
+
+## Sources
+
+All the references in the [further readings] section, plus the following:
+
+- [6 more terminal commands you should know]
+
+<!--
+  references
+  -->
+
+<!-- project -->
+<!-- article sections -->
+[further readings]: #further-readings
+
+<!-- knowledge base -->
+<!-- others -->
+[6 more terminal commands you should know]: https://betterprogramming.pub/6-more-terminal-commands-you-should-know-3606cecdf8b6

knowledge base/jot.md

@@ -0,0 +1,56 @@
+# `jot`
+
+Generates sequential or random data.
+
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
+## TL;DR
+
+```sh
+# Print 21 evenly spaced increasing numbers from -1 to 1.
+jot '21' '-1' '1.00'
+jot -p '2' '21' '-1' '1'
+
+# Print all ASCII characters.
+jot -c '128' '0'
+
+# Print all strings from 'xaa' to 'xaz'.
+jot -w 'xa%c' '26' 'a'
+
+# Print 20 random 8-letter strings.
+jot -r -c '160' 'a' 'z' | rs -g '0' '8'
+
+# Create files containing a bunch of 'x' characters for exactly 1024 bytes of
+# data.
+jot -b 'x' '512' > 'file.txt'
+
+# Print all lines of 80 characters or longer.
+grep $(jot -s "" -b '.' '80') 'file.txt'
+```
+
+## Further readings
+
+- [`man` page][man page]
+
+## Sources
+
+All the references in the [further readings] section, plus the following:
+
+- [6 more terminal commands you should know]
+
+<!--
+  references
+  -->
+
+<!-- project -->
+<!-- article sections -->
+[further readings]: #further-readings
+
+<!-- knowledge base -->
+<!-- others -->
+[6 more terminal commands you should know]: https://betterprogramming.pub/6-more-terminal-commands-you-should-know-3606cecdf8b6
+[man page]: https://manned.org/jot

knowledge base/log a terminal session.md

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+# Log (record) a terminal session
+
+See [`script`](script.md).

knowledge base/script.md

@@ -0,0 +1,56 @@
+# `script`
+
+Make a typescript file (a.k.a. log a.k.a. recording) of a terminal session.
+
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
+## TL;DR
+
+```sh
+# Start recording.
+# Defaults to a file named "typescript".
+script
+script 'file.log'
+
+# Stop recording.
+exit
+
+# Append to an existing file.
+script -a 'file.log'
+
+# Execute quietly.
+# Avoids 'start' and 'done' messages.
+script -q 'file.log'
+
+# Flush output after each write.
+script -f
+```
+
+## Further readings
+
+- [6 more terminal commands you should know]
+- [`man`][man]
+
+## Sources
+
+All the references in the [further readings] section, plus the following:
+
+- [cheat.sh]
+
+<!--
+  references
+  -->
+
+<!-- project -->
+<!-- article sections -->
+[further readings]: #further-readings
+
+<!-- knowledge base -->
+<!-- others -->
+[6 more terminal commands you should know]: https://betterprogramming.pub/6-more-terminal-commands-you-should-know-3606cecdf8b6
+[cheat.sh]: https://cheat.sh/script
+[man]: https://manned.org/script

knowledge base/ssh.md

@@ -55,6 +55,9 @@ ssh-add -L
 ssh-copy-id 'host.fqdn'
 ssh-copy-id -i "${HOME}/.ssh/id_rsa.pub" 'user@host.fqdn'
 
+# Preload trusted keys.
+ssh-keyscan 'host.fqdn' >> "${HOME}/.ssh/known_hosts"
+
 # Connect to an unreachable host tunnelling the session through a bastion.
 ssh -t 'bastion-host' ssh 'unreachable-host'