Add file_rhash utility

2 files changed, 15 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e31930f..9e5c2cd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   GNU+Linux distributions.
 - The `$BASHTARD_PLATFORM` variable now contains an additional entry, `init`, to
   allow for handling different init systems on GNU+Linux in a cleaner fashion.
+- A `file_rhash` utility function has been added, which will give you a hash based
+  on the file contents of a directory. This function will find files
+  recursively, calculate a hash for each of them, and then calculate a hash
+  based on the total result. The intended goal is to allow running before and
+  after templating some files, to deduce whether something actually changed.
 
 ### Changed
 
diff --git a/lib/util.bash b/lib/util.bash
index 6ad69e1..604e3e5 100644
--- a/lib/util.bash
+++ b/lib/util.bash
@@ -130,6 +130,16 @@ join_args() {
 	printf "%s" "$*"
 }
 
+# Recursively hash files in a directory, and hashing the output of all those
+# hashes again. This results in a single hash representing the state of files
+# in a directory. It can be used to check whether contents changed after
+# templating files in a given directory.
+file_rhash() {
+	find "$1" -type f -exec sha1sum {} \; \
+		| sha1sum \
+		| awk '{ print $1 }'
+}
+
 file_template()
 {
 	local file="$BASHTARD_ETCDIR/playbooks.d/$BASHTARD_PLAYBOOK/share/$1" ; shift