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#!/bin/bash
# whoneeds package : shows explicitly installed packages that require some package
# we use associative arrays to get uniqueness for "free"
typeset -A root_packages
typeset -A walked_nodes
query="$1"
function walk_nodes () {
local package="$1"
# if we've walked this node before, skip. This drastically
# reduces overhead for a relatively cheap operation
[[ "${walked_nodes[$package]}" -eq 1 ]] && return 0
walked_nodes["$package"]=1
# we do this so that we can make a single call to pacman
# to get both bits of information that we require
result=( $(LC_ALL=c pacman -Qi "$package" | awk -F':' \
'BEGIN { tag = ""; dependents = ""; explicit = 0 }
{
# since the formatting of the pacman output is more for human
# consumption than programmatic, we find ourselves with the following need.
# if we have two fields, then we know we have a proper identifier on the line
# so we store the identifier as a current tag
# All identifier checks are made against the current tag, which allows us
# to deal with instances where "Required By" spans lines
if (NF == 2) { tag = $1 }
if (tag ~ /^Required By[ ]*$/) { dependents = dependents $(NF) }
if ($1 ~ /^Install Reason $/ && $2 ~/^ Explicitly installed/) { explicit = 1 }
}
END { print explicit,dependents}') )
# and if we hit an issue retrieving package information
if [[ ${#result[*]} -lt 2 ]]; then
echo "error: could not get information on $package" 1>&2
exit 3
fi
if [[ ${result[0]} -eq 1 ]]; then
# we found an explicitly installed package that relies on
# the original query. Add it to our array, provided it isn't
# the original query, as that would be useless information
[[ "$query" != "$package" ]] && root_packages["$package"]=1
fi
if [[ "${result[1]}" != "None" ]]; then
# iterate over our 'Required By:' packages
dependents="${result[@]:1:${#result[*]}}"
for i in "$dependents"; do
walk_nodes "$i"
done
fi
}
if [ $# -ne 1 ]; then
echo "error: unexpected number of arguments" 1>&2
echo "Usage: $(basename $0) <package-name>"
exit 2
fi
walk_nodes "$1"
echo "Packages that depend on [$query]"
if [[ -n "${!root_packages[*]}" ]]; then
for pkg in "${!root_packages[@]}"; do
echo " $pkg"
done | sort
exit 0
fi
echo " None"
exit 1
# vim: set ts=4 sw=4 et:
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