jshn: improve performance by using let instead of $(( ))

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

diff --git a/sh/jshn.sh b/sh/jshn.sh
index 5db1667..f5cf1d2 100644 (file)
--- a/sh/jshn.sh
+++ b/sh/jshn.sh
@@ -42,7 +42,7 @@ _json_inc() {
        # var=$1
        # dest=$2
 
-       eval "${JSON_PREFIX}$1=\$(( \${${JSON_PREFIX}$1:-0} + 1))${2:+; $2=\"\$${JSON_PREFIX}$1\"}"
+       let "${JSON_PREFIX}$1 += 1" "$2 = ${JSON_PREFIX}$1"
 }
 
 _json_add_generic() {