feat: chapter 21 - Loops and working with Files and Folders

effective-shell-playground/scripts/common.sh

@@ -1,13 +1,13 @@
-# Write the title of our command.
-echo "common commands:"
-
 # If we are on a Mac, we need to use the GNU tools.
 if [[ "$(uname)" == "Darwin" ]]; then
     alias tail=gtail
     alias uniq=guniq
     alias sed=gsed
 fi
 
+# Write the title of our command.
+echo "common commands:"
+
 # The following variables control how the command runs.
 shell_binary=""    # We will work out what shell we are in later.
 history_file=""    # We will work out the history file later.
@@ -22,35 +22,49 @@ if [[ $SHELL =~ $shell_regex ]]; then
     if [[ $shell_binary == "bash" ]]; then
         history_file=~/.bash_history
     elif [[ $shell_binary == "zsh" ]]; then
-        history_file=~/.bash_history
+        history_file=~/.zsh_history
     fi
 fi
 
 # If we are searching through the bash history, we can look at the history file
 # to get the most common commands.
 if [[ $shell_binary == "bash" ]]; then
-    # Show the most commonly used commands.
-    tail "${history_file}" -n ${history_lines} \
+    # Store the most commonly used commands.
+    commands=$(tail "${history_file}" -n ${history_lines} \
         | sort \
         | uniq -c \
         | sed 's/^ *//' \
-        | sort -n \
-        | tail -n ${command_count}
+        | sort -n -r \
+        | head -n ${command_count})
 elif [[ $shell_binary == "zsh" ]]; then
     # Each line in the has some extra information at the beginning, the command
     # text only appears after a semi-colon. So extract the text from after the
     # semi-colon and then process it just like in the bash example.
+    commands=$(tail "${history_file}" -n ${history_lines} \
     tail "${history_file}" -n ${history_lines} \
         | rev \
         | cut -d';' -f1 \
         | rev \
         | sort \
         | uniq -c \
         | sed 's/^ *//' \
-        | sort -n \
-        | tail -n ${command_count}
+        | sort -n -r \
+        | head -n ${command_count})
 else
     # Show a warning to the user that we don't know where the history file is
     # for their shell.
     echo "Sorry, I don't know where to find the history for '${SHELL}'"
 fi
+
+# Print each command, showing what its order is in the list.
+# Commands are separated by newlines, so temporarily change IFS to loop over
+# each line of the commands.
+counter=1
+old_ifs=$IFS
+IFS=$'\n'
+for command in $commands
+do
+    echo "$counter: $command"
+    counter=$((counter + 1))
+done
+IFS=$old_ifs

effective-shell-playground/scripts/common.v1.sh

@@ -2,4 +2,4 @@
 echo "common commands:"
 
 # Show the most commonly used commands.
-tail ~/.bash_history -n 1000 | sort | uniq -c | sed 's/^ *//' | sort -n | tail -n 10
+tail ~/.bash_history -n 1000 | sort | uniq -c | sed 's/^ *//' | sort -n -r | head -n 10

effective-shell-playground/scripts/common.v2.sh

@@ -10,5 +10,5 @@ tail ~/.bash_history -n ${history_lines} \
     | sort \
     | uniq -c \
     | sed 's/^ *//' \
-    | sort -n \
-    | tail -n ${command_count}
+    | sort -n -r \
+    | head -n ${command_count}

effective-shell-playground/scripts/common.v3.sh

@@ -15,7 +15,7 @@ if [[ $SHELL =~ $shell_regex ]]; then
     if [[ $shell_binary == "bash" ]]; then
         history_file=~/.bash_history
     elif [[ $shell_binary == "zsh" ]]; then
-        history_file=~/.bash_history
+        history_file=~/.zsh_history
     fi
 fi
 
@@ -27,8 +27,8 @@ if [[ $shell_binary == "bash" ]]; then
         | sort \
         | uniq -c \
         | sed 's/^ *//' \
-        | sort -n \
-        | tail -n ${command_count}
+        | sort -n -r \
+        | head -n ${command_count}
 elif [[ $shell_binary == "zsh" ]]; then
     # Each line in the has some extra information at the beginning, the command
     # text only appears after a semi-colon. So extract the text from after the
@@ -40,8 +40,8 @@ elif [[ $shell_binary == "zsh" ]]; then
         | sort \
         | uniq -c \
         | sed 's/^ *//' \
-        | sort -n \
-        | tail -n ${command_count}
+        | sort -n -r \
+        | head -n ${command_count}
 else
     # Show a warning to the user that we don't know where the history file is
     # for their shell.

effective-shell-playground/scripts/common.v4.sh

@@ -0,0 +1,62 @@
+# Write the title of our command.
+echo "common commands:"
+
+# The following variables control how the command runs.
+shell_binary=""    # We will work out what shell we are in later.
+history_file=""    # We will work out the history file later.
+history_lines=1000 # The number of lines of history to search through
+command_count=10   # The number of common commands to show
+
+# Check to see if we can work out the name of the shell binary.
+shell_regex="([^/]+$)"
+if [[ $SHELL =~ $shell_regex ]]; then
+    # Depending on the name of the shell binary, set the history file path.
+    shell_binary=${BASH_REMATCH[1]}
+    if [[ $shell_binary == "bash" ]]; then
+        history_file=~/.bash_history
+    elif [[ $shell_binary == "zsh" ]]; then
+        history_file=~/.zsh_history
+    fi
+fi
+
+# If we are searching through the bash history, we can look at the history file
+# to get the most common commands.
+if [[ $shell_binary == "bash" ]]; then
+    # Store the most commonly used commands.
+    commands=$(tail "${history_file}" -n ${history_lines} \
+        | sort \
+        | uniq -c \
+        | sed 's/^ *//' \
+        | sort -n -r \
+        | head -n ${command_count})
+elif [[ $shell_binary == "zsh" ]]; then
+    # Each line in the has some extra information at the beginning, the command
+    # text only appears after a semi-colon. So extract the text from after the
+    # semi-colon and then process it just like in the bash example.
+    commands=$(tail "${history_file}" -n ${history_lines} \
+        | rev \
+        | cut -d';' -f1 \
+        | rev \
+        | sort \
+        | uniq -c \
+        | sed 's/^ *//' \
+        | sort -n -r \
+        | head -n ${command_count})
+else
+    # Show a warning to the user that we don't know where the history file is
+    # for their shell.
+    echo "Sorry, I don't know where to find the history for '${SHELL}'"
+fi
+
+# Print each command, showing what its order is in the list.
+# Commands are separated by newlines, so temporarily change IFS to loop over
+# each line of the commands.
+counter=1
+old_ifs=$IFS
+IFS=$'\n'
+for command in $commands
+do
+    echo "$counter: $command"
+    counter=$((counter + 1))
+done
+IFS=$old_ifs

structure.md

@@ -31,8 +31,7 @@ This document contains the proposed structure of the book. It is still work in p
         * [Chapter 18 - Shell Script Fundamentals](#chapter-18---shell-script-fundamentals)
         * [Chapter 19 - Variables, Reading Input, and Mathematics](#chapter-19---variables-reading-input-and-mathematics)
         * [Chapter 20 - Mastering the If Statement](#chapter-20---mastering-the-if-statement)
-        * [Chapter 20 - Logic, Loops and working with Files and Folders](#chapter-20---logic-loops-and-working-with-files-and-folders)
-        * [Chapter 20 - Loops and working sets of Files and Folders](#chapter-20---loops-and-working-sets-of-files-and-folders)
+        * [Chapter 20 - Loops and working with Files and Folders](#chapter-20---loops-and-working-with-files-and-folders)
         * [Chapter 21 - Getting Input from the User and using Variables](#chapter-21---getting-input-from-the-user-and-using-variables)
         * [Chapter X - Parameters, Return Values, Error Handling](#chapter-x---parameters-return-values-error-handling)
         * [Chapter 23 - Logic and Mathematics](#chapter-23---logic-and-mathematics)
@@ -48,6 +47,7 @@ This document contains the proposed structure of the book. It is still work in p
     * [Interlude - The Unix Philosophy](#interlude---the-unix-philosophy)
     * [Interlude - The Linux and Shell Family Tree](#interlude---the-linux-and-shell-family-tree)
     * [Part 6 - Advanced Techniques](#part-6---advanced-techniques)
+        * [Understanding Shell Expansions](#understanding-shell-expansions)
         * [Chapter 26 - Managing Multiple Programming Languages with Make](#chapter-26---managing-multiple-programming-languages-with-make)
         * [Chapter 27 - The Power of Terminal Editors](#chapter-27---the-power-of-terminal-editors)
         * [Chapter 28 - The Multiplexer](#chapter-28---the-multiplexer)
@@ -69,6 +69,7 @@ This document contains the proposed structure of the book. It is still work in p
     * [The Most Important Manpages](#the-most-important-manpages)
     * [Appendixes](#appendixes)
         * [Appendix 1: Shell Shortcuts](#appendix-1-shell-shortcuts)
+        * [Appendix 2: Shell Parameter Expansion](#appendix-2-shell-parameter-expansion)
 * [More Useful Reading](#more-useful-reading)
 * [Essential Tools](#essential-tools)
 * [Good Scripts to write as exercises](#good-scripts-to-write-as-exercises)
@@ -214,11 +215,7 @@ We've seen variables a few times in our journey so far. In this chapter we'll lo
 
 In this chapter we'll introduce the _if statement_ - this is a crucial feature of the shell as it allows us to create perform operations only when certain conditions are met. First we'll look at the basics of how the statement is used and then look at some more advanced scenarios.
 
-#### Chapter 20 - Logic, Loops and working with Files and Folders
-
-One of the most common tasks we will do when scripting is operating functions over a set of files or folders. In this chapter we'll look at basic loops, tests and how to operate on many files. We'll also see how we can integrate commands like `find` into shell scripts.
-
-#### Chapter 20 - Loops and working sets of Files and Folders
+#### Chapter 20 - Loops and working with Files and Folders
 
 One of the most common tasks we will do when scripting is operating functions over a set of files or folders. In this chapter we'll look at basic loops, tests and how to operate on many files. We'll also see how we can integrate commands like `find` into shell scripts.
 
@@ -289,6 +286,10 @@ There are lots of different flavours of Linux and Unix, and lots of different sh
 
 The more time you spend in the shell, the more effective you may well find yourself. If you are benefiting from your shell chops, this section contains suggestions for deeper topics to look into, which can take you even further.
 
+#### Understanding Shell Expansions
+
+https://www.gnu.org/software/bash/manual/html_node/Shell-Expansions.html#Shell-Expansions
+
 #### Chapter 26 - Managing Multiple Programming Languages with Make
 
 GNU Make can be a powerful tool for anyone who uses multiple programming languages, or wants to make it easier to allow people to use their projects. In this chapter we'll look at some common patterns which we can use `make` for to make our lives easier when working with different programming languages and platforms.
@@ -407,6 +408,10 @@ As an appendix, or printed reference, list of the top ten manpages?
 
 (This is the cheat sheet from 'fly on the command line'.)
 
+#### Appendix 2: Shell Parameter Expansion
+
+Show the order of shell parameter expansion and an example of each one. This would actually be good as a pull-out reference.
+
 
 This section contains the things which have been pulled out of chapters as they made them too big, or don't fit in a chapter yet:
 
@@ -491,6 +496,11 @@ This section contains the things which have been pulled out of chapters as they
 - todo: chapter 7 talks about control characters (specifically, ^D), maybe we put this in the 'processes' section?
 - todo: slice and dice: add count option (-c) for `uniq` and numeric (-n) for `sort` as we use these commands in the shell script essentials chapter
 - todo: we need to show the `ln` command. It is used in the shell script essentials chapter.
+- todo: chained commands: `git pull && git checkout`, chained OR, OR true
+- todo: more portable sed:
+      -	sed -i '' 's/%%ES_SCRIPT_VERSION%%/$(shell cat version.txt)/' build/index.html
+    +	perl -i -pe's/%%ES_SCRIPT_VERSION%%/$(shell cat version.txt)/' build/index.html
+
 
 ## More Useful Reading