Sharing (this but not food) is caring (Bash scripting cheatsheet)

[williamwlk]

Hey Folks,

This is good. A real good cheat sheet for Bash.

https://devhints.io/bash

Cheers.

Will

[Deanna]

Thank you for sharing @williamwlk! Very valuable resource indeed. 

[williamwlk]

My pleasure @Deanna :) and echo your comment (Very valuable resource indeed.).

Will

[Jeff_Schaller]

Beware of unquoted variable expansions shown as example on that page. For example,

for i in "${arrayName[@]}"; do
  echo $i
done

Should be:

for i in "${arrayName[@]}"; do
  printf '%s\n' "$i"
done

 To see why, create a file named "file1" somewhere:

    cd /tmp

    touch file1

Then create an array like this (note that array element zero is the string "file*"; no filename expansion yet):

    arrayName=('file*')

And then unsafely  run the sample for loop; you'll get:

    for i in "${arrayName[@]}"; do echo $i; done
    file1 

You "accidentally" ran into filename expansion (globbing) when weren't expecting it.

Next, consider using printf instead of echo. Load the array this way:

    arrayName=('-e')

and then run the loop; even with proper quoting, you'll get:

    for i in "${arrayName[@]}"; do echo "$i"; done

... with a blank line! Using printf instead gets you the actual data:

    for i in "${arrayName[@]}"; do printf '%s\n' "$i"; done
    -e

[oldbenko]

Hey, @Jeff_Schaller,

Well spotted! I have also noticed some weirdness such as:

• the entire section on conditionals suggests double square brackets but never explains the difference between "[[" and "[" (both are builtins, but "[" is more portable)
• the section on getting options should use the getopts builtin, everything else is a poor hack
• the arrays section should explain shift and unshift, not the options one

And of course, whatever is already in the comments.