Patterns for usage of linux and cli tools

Configure all ReadLine based programs to use vi mode

Examples: bash shell, psql cli

1. Create a file ~/.inputrc
2. Add set editing-mode vi

one-liner

echo 'set editing-mode vi' >> ~/.inputrc

Edit a command in vim

Sometimes when you type a long command you make a mistake or simply want to rerun a command which is very similar to a previous command. There are 2 ways:

1. Use vi mode in bash

This is the simplest. Simply use ESC to enter normal mode emulation and most keybindings are available.

2. Edit the command in vim

This is when you want the full power of vim. Hit ESC to enter normal mode, then v to open the command in the vim editor in a temporary file.

Testing conditions

Use 2 opening brackets, space, value 1, comparison option, value 2, space 2 closing brackets.

Example:

if [[ $FOO -lt 10 ]] then
  echo "1 digit"
elif [[ $FOO -lt 100 ]] then
  echo "2 digits"
else
  echo "more than 2 digits"
fi

Redirects are for files (or file-like things)

Examples:

# send stdout to a file
echo "foo" > file.txt

# send file to stdin
< file.txt grep "something"

# send the output of a command to a file-like, redirected to stdin
<(ls -l ./dir1) grep "somefile"

# send the output of commands directly to command positional args and redirect stdout to a file

diff <(ls -l ./dir1) <(ls -l ./dir2) > diff.txt

Default script options

Certain settings improve bash script behaviors

set -o errexit        # exit the script if an error occurs
set -o xtrace         # print each command as it runs
set -o nounset        # prevent using variables that aren't unset

Dry run a bash script

Use the -n option to perform a dry run. Useful for e.g. syntax checking

bash -n myscript.sh

Shellcheck

Use coc-sh or some other bash-language-server client that leverages shellcheck.

Using arrays

Regular Example:

inputs=(1 2 4 8 16 32 64 128)
outputs=()
for i in ${inputs[@]}; do
  rs=$(./foocmd $i)
  output+=( $rs )
done

Associative Array Example:

Everything is an array in bash

foo=(1 2 3 4 5)
echo $foo
# outputs 1

Basically a variable reference with no index is desugared to $variable[0].

To expand the whole array:

foo=(1 2 3 4 5)
echo ${foo[@]}
# outputs 1 2 3 4 5

Grab a module from one git branch into another

See (https://github.com/OCA/maintainer-tools/wiki/Migration-to-version-15.0)[https://github.com/OCA/maintainer-tools/wiki/Migration-to-version-15.0]

git format-patch --keep-subject --stdout origin/15.0..origin/14.0 -- $MODULE | git am -3 --keep

Git push with personal access token

1. Create a github personal access token and copy it somewhere.

2. Create a git remote using the https protocol

git remote add https https://github.com/somerepo.git

3. Push

git push https <branch>

You will be prompted for an access token, serving as your password

Git commit as specific author

git -c user.name="Zach Waite" -c user.email="zach@waiteperspectives.com" commit -m "Test commit"

Git push as specific author

git push <remote> <branch> --author "Zach Waite <zach@waiteperspectives.com>"

Git push when not on a branch

git push <remote> HEAD:<branch>