which-hunt - an alternative to 'which' that traces symlinks and shims

which-hunt.sh

#!/bin/bash
# Copyright 2023 Rich Dougherty

# which-hunt - an alternative to 'which' that traces symlinks and shims

# - Examples -
#
# $ which java
# /usr/bin/java
#
# $ which-hunt java
# /usr/lib/jvm/java-17-openjdk-amd64/bin/java
#
# $ which-hunt -v java
# /usr/bin/java (link)
# /etc/alternatives/java (link)
# /usr/lib/jvm/java-17-openjdk-amd64/bin/java
#
# $ which-hunt -v python
# /home/rich/.pyenv/shims/python (pyenv)
# /usr/bin/python (link)
# /usr/bin/python3 (link)
# /usr/bin/python3.10

# The which-hunt script is a utility for tracing the actual executable file 
# that a command points to in Unix-like operating systems. It handles both
# symlink chains as well as shim-based version manager setups (like pyenv, jenv, etc).
# The script supports verbose output which includes the type of each link in the chain 
# and employs color coding (if supported by the terminal and not piped to commands like 'less') 
# for better readability. The script also manages relative paths and converts them to 
# absolute paths during the trace.

# Function to check if the script's output is being piped
is_piped() {
  [[ ! -t 1 ]]
}

# Determine color support and whether to enable color output (disable if piped)
COLOR_SUPPORTED=$(tput colors 2>/dev/null || echo 0)
COLOR_ENABLED=$(( COLOR_SUPPORTED >= 8 && ! is_piped ))
verbose=0

# Function to output colored text (if enabled)
color() {
    if (( COLOR_ENABLED )); then
        echo -ne "\e[${1}m"
    fi
}

# Function to output verbose text (if verbose mode is enabled)
verbose_output() {
    if [[ $verbose -eq 1 ]]; then
        echo -e "$1"
    fi
}

# Display usage information and exit with a status of 1 (indicating an error)
usage() {
    echo "Usage: $0 [-v|--verbose] <command>"
    exit 1
}

# Check if at least one argument is supplied, otherwise display usage and exit
if [[ $# -lt 1 ]]; then
    usage
fi

# Parse the supplied arguments (verbose flag and command to trace)
while [[ $# -gt 0 ]]; do
    key="$1"

    case $key in
        -v|--verbose)
        verbose=1
        shift
        ;;
        -h|--help)
        usage
        ;;
        *)
        cmd="$1"
        shift
        ;;
    esac
done

# If no command is specified, display usage information and exit with error status
if [[ -z $cmd ]]; then
    usage
fi

# Get the initial path of the command using 'which'
current_path=$(which -- "$cmd" 2>/dev/null)
if [[ -z $current_path ]]; then
    echo "Error: Command '$cmd' not found"
    exit 1
fi

# Main loop to trace the command through any symlink or shim chains
# Main loop to trace the command through any symlink or shim chains
while : ; do
if [[ $current_path == $HOME/.*/shims/* ]]; then
        shim_mgr=${current_path#*$HOME/.}
        shim_mgr=${shim_mgr%%/shims/*}
        link_type="$shim_mgr"
        next_path=$("$shim_mgr" which "$cmd")
    elif [[ -L $current_path ]]; then
        link_type="link"
        next_path=$(readlink -- "$current_path")
        # Ensure that the next path is an absolute path
        if [[ ! $next_path == /* ]]; then
            next_path=$(dirname -- "$current_path")/"$next_path"
        fi
    else
        break
    fi

    verbose_output "$(color 36)${current_path}$(color 0) $(color 33)(${link_type})$(color 0)"
    current_path="$next_path"
done

# Output the final resolved path of the command
echo "$current_path"