Bash manual page selection menu I wrote the following script in the hopes of streamlining the finding and reading of multiple manual pages. Since I am always looking up different utilities' manual pages I thought this would a good learning aid.

#!/bin/bash

while true
do
    echo
    echo "1) /bin"
    echo "2) /sbin"
    echo "3) /usr/bin/"
    echo "4) /usr/sbin"
    echo "5) /usr/local/bin"
    echo "6) /usr/local/lib"
    echo "7) /usr/local/share"
    echo "8) /usr/local/include"
    echo "9) exit"
    echo
    read -p 'Select a directory ' d
    if [[ $d = 1 ]]; then
        dir=/bin
    elif [[ $d = 2 ]]; then
        dir=/sbin
    elif [[ $d = 3 ]]; then
        dir=/usr/bin
    elif [[ $d = 4 ]]; then
        dir=/usr/sbin
    elif [[ $d = 5 ]]; then
        dir=/usr/local/bin
    elif [[ $d = 6 ]]; then
        dir=/usr/local/lib
    elif [[ $d = 7 ]]; then
        dir=/usr/local/share
    elif [[ $d = 8 ]]; then
        dir=/usr/local/include
    elif [[ $d = 9 ]]; then
        exit
    else
        echo 'No such directory'
        exit 1
    fi
    echo
    while true
    do
        menu=( $(ls -1 ${dir}) )
        i=0
        for m in ${menu[@]}
        do 
            echo "$(( i++ ))) $(basename $m)"
        done | xargs -L3 | column -t
        echo
        echo 'Select from the list above'
        echo 'Type b to go back to main menu'
        read -p 'Type q to quit at anytime ' n
        echo
        if [[ $n = 'b' || $n = 'B' ]]; then 
            break 1
        elif [[ $n = 'q' || $n = 'Q' ]]; then
            exit
        else 
            for item in ${menu[$n]}
            do 
                if [[ $item =~ '.txt' ]]; then
                    item="$(echo ${item%.*})"
                fi
                man $item
            done
        fi
    done
done


One thing I should point out. My /usr/local/bin directory has several .txt files. That is the reason for if [[ $item =~ '.txt' ]]; then item="$(echo ${item%.*})"; fi Maybe it is normal to have plain text files in this directory or maybe this is something I did unintentionally when experimenting writing this script. (An earlier version of this script wrote all the man pages to plain text files.) I really don't know but that's why that part of the script is there. 

I think this script does what I hoped it would do so now I would like other people's opinion. Is there anything I could do better? Am I overlooking anything?
Use a table driven menu

The menu to select from /bin, /sbin and other is very repetitive.
A table-based approach would be more compact, easier to write and maintain.
Try to use an array, as you did in other places of the script.

First, put the directories in an array, for example:

dirs=('' /bin /sbin /usr/bin)  # fill the rest


Note that I added a dummy empty first element.
This is to make the 1-based indexes of your menu work with the 0-based array indexes.

Build the menu from this array using a counting loop from 1, the first non-empty element:

for ((index = 1; index &lt; ${#dirs[@]}; index++)); do
    echo "$index) ${dirs[$index]}"
done


To validate the user input, simply check if ${dirs[$index]} is empty.
If yes, the input is invalid.

Security


  Maybe it is normal to have plain text files in this directory or maybe this is something I did unintentionally when experimenting writing this script. (An earlier version of this script wrote all the man pages to plain text files.)


No, it is not normal to have .txt files in any of those directories.
So I guess your earlier script put them there.
But a normal user should not have write access to these directories.
Which seems to suggest that you're playing with a privileged account,
possibly root.
That's a bad idea, avoid using root casually.

Simplify

You can simplify [[ $n = 'b' || $n = 'B' ]] using pattern matching: [[ $n == [bB] ]].

Strangeness

You don't need the -1 here.


menu=( $(ls -1 ${dir}) )



When inside $(...), ls does not columnize its output.



In this code, I don't see why you need basename:


echo "$(( i++ ))) $(basename $m)"



It seems the value of $m will always be a simple filename without a path part.