From 31fb248fc6916f3988d99c10220ba42cf432611b Mon Sep 17 00:00:00 2001
From: Matthias Kruk <m@m10k.eu>
Date: Thu, 15 Apr 2021 22:35:00 +0900
Subject: [PATCH] include/sem: Add sem_peek() function

This commit adds the sem_peek() function, which allows the caller to
determine the value of a semaphore without modifying it.
---
 include/sem.sh | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/include/sem.sh b/include/sem.sh
index 4a04134..b59ac13 100644
--- a/include/sem.sh
+++ b/include/sem.sh
@@ -236,3 +236,31 @@ sem_post() {
 
 	return "$err"
 }
+
+sem_peek() {
+	local name="$1"
+
+	local mutex
+	local sem
+	local value
+	local err
+
+	mutex=$(_sem_mutexpath "$name")
+	sem=$(_sem_sempath "$name")
+	err=false
+
+	mutex_lock "$mutex"
+
+	if ! value=$(<"$sem"); then
+		err=true
+	fi
+
+	mutex_unlock "$mutex"
+
+	if "$err"; then
+		return 1
+	fi
+
+	echo "$value"
+	return 0
+}
-- 
2.47.3