Add summary table for commands in each section

lessons/shell/creating-things.md

@@ -1 +1,23 @@
+![ESPIn logo](../../media/ESPIn.png)
+
 # Creating things
+
+
+## Summary
+
+The table below summarizes the commands and keyboard shortcuts
+described in this section.
+
+| Command/Shortcut | Description
+| ---------------- | -----------
+| mkdir            | creates a directory
+| touch            | creates an empty file
+| nano             | text editor
+| rm               | deletes a file (permanently)
+| rmdir            | deletes a directory (permanently)
+| mv               | moves or renames a file
+| cp               | copies a file
+| Ctrl-a           | place cursor at start of line
+| Ctrl-e           | place cursor at end of line
+| Ctrl-k           | clear text to end of line
+| Ctrl-l           | clear text in terminal

lessons/shell/files-and-directories.md

@@ -1 +1,27 @@
+![ESPIn logo](../../media/ESPIn.png)
+
 # Files and directories
+
+The operating system on a computer is comprised of files.
+
+
+## Summary
+
+The table below summarizes the commands and special characters
+described in this section.
+
+| Command/Character | Description
+| ----------------- | -----------
+| pwd               | print working directory
+| ls                | directory listing
+| cd                | change directory
+| /                 | path delimiter
+| ~                 | home directory
+| .                 | current directory
+| ..                | one directory up
+| -                 | previous directory
+| pushd             | push directory on stack
+| popd              | pop directory off stack
+| dirs              | print directory stack
+| tree              | view directory tree *(nonstandard)*
+| tab               | complete command

lessons/shell/finding-things.md

@@ -1 +1,22 @@
+![ESPIn logo](../../media/ESPIn.png)
+
 # Finding things
+
+
+## Summary
+
+The table below summarizes the commands, keyboard shortcuts,
+and special characters described in this section.
+
+| Command/Shortcut | Description
+| ---------------- | -----------
+| grep             | match text in files
+| find             | match filenames
+| history          | record of commands
+| Ctrl-r           | reverse search through history
+| !                | repeat command from history
+| man              | show documentation for command
+| env              | show environment variables
+| echo             | print variables to terminal
+| which            | show location of command
+| alias            | make a shortcut for a command

lessons/shell/getting-things.md

@@ -1 +1,18 @@
+![ESPIn logo](../../media/ESPIn.png)
+
 # Getting things from elsewhere
+
+
+## Summary
+
+The table below summarizes the commands described in this section.
+
+| Command  | Description
+| -------- | -----------
+| curl     | get files from an URL
+| wget     | get files from an URL (nonstandard)
+| rsync    | get files from remote machine
+| ssh      | login to remote machine
+| zip      | package and compress/uncompress files
+| gzip     | package and compress/uncompress files
+| tar      | package and compress/uncompress files

lessons/shell/pipes-and-filters.md

@@ -1 +1,24 @@
+![ESPIn logo](../../media/ESPIn.png)
+
 # Pipes and filters
+
+
+## Summary
+
+The table below summarizes the commands and special characters
+described in this section.
+
+| Command/Character | Description
+| ----------------- | -----------
+| cat               | dump text to terminal
+| more              | screen pager
+| less              | better screen pager
+| head              | print first lines of file
+| tail              | print last lines of file
+| wc                | count characters, words, lines
+| |                 | pipe output of command
+| >                 | redirect output of command
+| *                 | match all characters
+| ?                 | match single characters
+| sort              | sorts input
+| sed               | stream editor