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@pinealan
Last active Apr 19, 2020
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Diff installed packages between nix generations
#!/usr/bin/env bash
# From https://github.com/pinealan/dotfiles
nix-list() {
nix-env --list-generations
}
get_current_gen() {
if [ -z $1 ] ; then
# default to current generation of nix-env
nix-list | grep current | awk '{print $1}'
else
# get n-th last generation
nix-list | grep -B $1 current | head -n 1 | awk '{print $1}'
fi
}
verify_gen_exist() {
if ! nix-list | awk '{print $1}' | grep $1 > /dev/null ; then
echo "Error: generation $1 not found." >&2
exit 1
fi
}
# This function needs to be run one at a time.
# It make changes to filesystem (i.e. touches /nix/var/<user>/profile symlink),
# so running it multiple times in the same command could lead concurrent
# invocation that fails due to a lock on the file
echo_nix_gen_pkgs() {
local original_gen=$(get_current_gen)
nix-env -G $1 2> /dev/null
nix-env -q
nix-env -G $original_gen 2> /dev/null
}
main() {
# Select diff command
if hash icdiff 2>/dev/null ; then
icdiff -L $from_gen -L $to_gen $1 $2
elif ! hash diff 2>/dev/null ; then
echo "Error: diff or icdiff not installed." >&2
exit 1
elif hash grc 2>/dev/null ; then
grc diff $1 $2 || true
else
diff $1 $2 || true
fi
}
# Select diff-ed generations
if [ -z $1 ] ; then
from_gen=$(get_current_gen 1)
else
verify_gen_exist $1
from_gen=$1
fi
if [ -z $2 ] ; then
to_gen=$(get_current_gen)
else
verify_gen_exist $2
to_gen=$2
fi
# see function comments on separating these invocations
old=$( echo_nix_gen_pkgs $from_gen )
new=$( echo_nix_gen_pkgs $to_gen )
# main
main <(echo $old | tr ' ' '\n') <(echo $new | tr ' ' '\n')
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pinealan commented Apr 12, 2020

When icdiff is installed:
image
When invoked with no arguments, diff is between current and previous generation.

To diff between current and specific generations

nix-env-diff <from_gen>

image

Diff between 2 specific generations

nix-env-diff <from_gen> <to_gen>

image

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