Myron's Dev Notes

BASH Notes

Shared setup

# sample shared .bashrc and aliases
[ -e ~/.bash/bashrc ] && . ~/.bash/bashrc
[ -e ~/.bash/aliases.sh ] && . ~/.bash/aliases.sh

Source and Export Variables

set -a; source .env; set +a

Exit on Error

#! /bin/bash -eu
set -o pipefail

Local Variables

func() {
  local arg1="${1}"
  local x="${2%/}"

Run command as user that does not have a shell

su - -s /bin/bash tomcat8

Lots of shell trickery

Array examples

declare -A aliases
aliases=(
	[mainline]='1 1.13 latest'
	[stable]='1.12'
)
versions=( */ )
versions=( "${versions[@]%/}" ) # add to existing

Resolve path to script

# Need to play with this
self="$(basename "$BASH_SOURCE")"
cd "$(dirname "$(readlink -f "$BASH_SOURCE")")"

check remote shell vars

echo env |ssh -T mdc |grep TARG

Test Arg processing

file mro.2

#!/bin/sh
echo -------------
for f in "$@"; do
    echo \"$f\"
done

file mro.1

#!/bin/sh

function command () {
    echo
    echo "command line: $@"
    echo "command output:"
    echo "-------------------------------"
    "$@"
    code=$?
    echo "-------------------------------"
    return $code
}

Tests

./mro.2 a b c
./mro.2 "a b" c
./mro.2 a "b c"

command ./mro.2 a b c
command ./mro.2 "a b" c
command ./mro.2 a "b c"

Option processing

OPTIND=1
while getopts "hdp" opt; do
    case "$opt" in
        h)   usage ;;
        '?') usage ;;
        d) PROFILE=dev ;;
        p) PROFILE=prod ;;
        :)
            echo "Option -$OPTARG requires an argument." >&2
            exit 1
            ;;
    esac
done
shift "$((OPTIND-1))" # Shift off the options and optional --.

Gen random strings

export CHART_BUCKET=s3://example-chart-store-$(cat /dev/random | LC_ALL=C tr -dc "[:alpha:]" | tr '[:upper:]' '[:lower:]' | head -c 32)

openssl rand 16 -hex
node -e "console.log(require('crypto').randomBytes(256).toString('base64'));"
uuidgen
pwgen 50 1 -s > passphrase
# Or use KeePassX generator

ruby -rsecurerandom -e 'puts SecureRandom.hex(32)'

cat /proc/sys/kernel/random/uuid

Sequence

for i in {0..9}; do echo $i; done
for i in `seq 1 5`;do x; done

list completions

complete #list
complete -F _asdf b # assign to function

load completion functions from tools like eksctl

. <(eksctl completion bash)

Base dir

DIR=$(dirname $([ -L $0 ] && readlink $0 || echo $0))
DIR=$(cd $DIR>/dev/null; pwd -P)

dump env and functions

typeset

see definitions

type <str>

Tail a file from the beginning

tail -0F

Sample xargs

echo webserver loadbalancer database | tr ' ' '\n' \
| xargs -I % -P 3 bash -c 'ansible-playbook $1.yml' -- %

remove root from list of files