hook.sh

Seamlessly extend any command with pre and post command hooks using vanilla bash.

hook.sh will try to find and execute pre and post functions matching the arguments passed to the hook command.

Features

• Pre and Post hooks for any command
• Local hooks defined in hooks.sh relative to the current directory.
• Global hooks defined in a .sh that can be placed anywhere and defined by setting the HOOK_GLOBAL_FILE environment variable (must use a full path).
• Hook a command or a command with a specific set of arguments.
• Configurable: Override hook prefixes, filenames, and more.
• Logging available when setting HOOK_LOG environment variable to true.
• Custom logging and log level filtering by replacing the default logger using HOOK_LOG_FUNC.

Configuration

NOTE: Override defaults by setting evironment variables in your shell before sourcing hook.sh.

Variable	Default value	Description
HOOK_FILE	./hooks.sh	The relative path to a local hooks file.
HOOK_PREFIX	hook_	The function name prefix used to identify a local hook and avoid collisions with other functions.
HOOK_GLOBAL_FILE	-	The path to a global hooks file.
HOOK_GLOBAL_PREFIX	global_	The function name prefix used to identify a global hook and avoid collisions with other functions. The final function name needs to be prefixed with both the global and local prefix (ie. global_hook_pre_terraform)
HOOK_LOG	false	When set to true, hook.sh will output debug logs.
HOOK_LOG_FUNC	_hook_log_msg	The name of the function used by hook to log message.

Usage

1. Create a hooks.sh file in the directory where you want to run a command.
2. Create hook_pre* and/or hook_post* functions matching the command name and arguments you want to hook.
3. Source the hook.sh library in your shell.
4. Go to the directory where you created your hooks.sh file and run your command, prefixing it with the word hook.

Example

./examples/terraform/hooks.sh

#!/usr/bin/env bash

hook_pre() {
  echo 'Always running before any command...'
}

hook_pre_terraform() {
  echo 'Always running before any terraform command...'
}

hook_pre_terraform_apply() {
  echo 'Running before terraform apply...'
}

hook_post_terraform_destroy() {
  echo 'Running after terraform destroy...'
}

bash

source ./hook.sh
cd ./examples/terraform/
alias terraform='hook terraform'
terraform init
terraform apply

output

Always running before any command...
Always running before any terraform command...
[terraform init ...]
Always running before any command...
Always running before any terraform command...
Running before terraform apply...
[terraform apply ...]

Logging

To enable internal logging from hook.sh, set the environment variable HOOK_LOG to true.

Log levels

The following log levels are used by hook.sh and is always the first argument passed to the log HOOK_LOG_FUNC.

• TRACE
• DEBUG
• INFO
• WARN
• ERROR

Custom logger

To enable the use of a custom logger, simply set the HOOK_LOG_FUNC to the name of a function or binary that can handle logging for you.

awesome_log() {
  echo "[awesome-log] [$1] ${*:2}" ;;
}
export HOOK_LOG_FUNC='awesome_log'

Log level filtering

He're an example of how to set up log level filtering using a custom logger:

filtered_log() {
  case $1 in
    TRACE | DEBUG) ;; # log nothing
    *) echo "[$1] ${*:2}" ;;
  esac
}
export HOOK_LOG_FUNC='filtered_log'