From 27133b73f484d3cf2a94a174cc0ca695d2de7938 Mon Sep 17 00:00:00 2001
From: Karl Bartel <karl.bartel@clabs.co>
Date: Tue, 12 Nov 2024 16:20:39 +0100
Subject: [PATCH] progress: Avoid accidental early return

expr returns a non-zero exit code if it's calculated value is zero. This
is surprising and usually not what you want. In this case, it will lead
to the script terminating early for some values (e.g. HOURS=0). Small
example to show the problem:

```
> bash -c 'HOURS=`expr 0` && echo true || echo false'
false
```

Fortunately, bash has the arithmetic calculation syntax $((...)) that
behaves as intended.
---
 progress.sh | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/progress.sh b/progress.sh
index 1e33b23..a09bacb 100755
--- a/progress.sh
+++ b/progress.sh
@@ -36,9 +36,9 @@ fi
 
 # How many more blocks do we need?
 HEAD=`cast block-number --rpc-url $L2_URL`
-BEHIND=`expr $HEAD - $T1`
-MINUTES=`expr $BEHIND / $PER_MIN`
-HOURS=`expr $MINUTES / 60`
+BEHIND=$((HEAD - T1))
+MINUTES=$((BEHIND / PER_MIN))
+HOURS=$((MINUTES / 60))
 
 if [ $MINUTES -le 60 ] ; then
    echo Minutes until sync completed: $MINUTES