bash_tips

base.sh

#!/usr/bin/env bash

# https://github.com/kward/shflags
# https://odb.github.io/shml/getting-started/#Install

# Path to script directory
__dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"

# shellcheck disable=SC1090
source "${__dir}/lib/shml.sh"

# shellcheck disable=SC1090
source "${__dir}/lib/shflags.sh"

function usage()
{
    echo "......."
    echo "$0 [-v VERSION]"
}

function info()
{
    local MSG
    MSG="[$(date +%Y-%m-%d\ %H:%M:%S)] $*"
    # shellcheck disable=SC2046
    echo $(fgcolor blue "$MSG") $(bgcolor end)
}

function error()
{
    local MSG
    MSG="[$(date +%Y-%m-%d\ %H:%M:%S)] $*"
    # shellcheck disable=SC2046
    echo $(fgcolor red "$MSG") $(bgcolor end)
}

yell() { echo "Error with the command $0: $*" >&2; }
die() { yell "$*"; exit 111; }
try() { "$@" || die "cannot $*"; }

# Action
DEFINE_boolean 'create' false 'Create ......' 'c'

# Manage help message without argument
if [ $# == 0 ] ; then
    flags_help
    exit 1;
fi

# Parse arguments
FLAGS "$@" || exit 1
eval set -- "${FLAGS_ARGV}"

# shellcheck disable=SC2154
if [ "${FLAGS_create}" -eq "${FLAGS_TRUE}" ]; then
    #....
fi

bash_tips.md

Bash focus point

set -e, -u, -o pipefail

set -euo pipefail

• set -e The set -e option instructs bash to immediately exit if any command [1] has a non-zero exit status.

• set -u set -u affects variables. When set, a reference to any variable you haven't previously defined is an error, and causes the program to immediately exit

• set -o pipefail This setting prevents errors in a pipeline from being masked. If any command in a pipeline fails, that return code will be used as the return code of the whole pipeline. By default, the pipeline's return code is that of the last command

• https://gist.github.com/mohanpedala/1e2ff5661761d3abd0385e8223e16425

• https://vaneyckt.io/posts/safer_bash_scripts_with_set_euxo_pipefail/

Bash Manuel

Special parameter

https://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html#Special-Parameters

Snippets

xargs template

Define a place holder with the -I option

echo "this is a basic xargs example" | xargs -I {} echo "you said: {}"

run a bash function with the timeout command

function my_function {
    until kubectl get -n kube-system deploy/my_dep ; do
        echo "Wait my_dep deployment ..."
        sleep 5
    done

    # Do someting
    
}

export -f my_function
timeout 20s bash -c my_function