Fix arithmetic error in scroll causing crash

1 files changed, 12 insertions, 6 deletions

@@ -1,8 +1,8 @@
-#!/bin/sh
+set +x
 
 readc() { # arg: <variable-name>
         # adapted from https://unix.stackexchange.com/a/464963
-        if [ -t 0 ]; then
+        if test -t 0 ; then
                 # if stdin is a tty device, put it out of icanon, set min and
                 # time to sane value, but don't otherwise touch other input or
                 # or local settings (echo, isig, icrnl...). Take a backup of the
@@ -97,8 +97,9 @@ notify_flush() { # notify_flush
 }
 
 scroll() { # scroll nlines -- MUTATES GLOBAL STATE
-        case "${1:-0}" in
-                \+*|\-*) n=$((n+$1)) ;;
+        arg="${1:-0}"
+        case "$arg" in
+                +*|-*) n=$((n+${arg#+})) ;;
                 0) ;;
                 *) n=$1 ;;
         esac
@@ -116,7 +117,7 @@ scroll() { # scroll nlines -- MUTATES GLOBAL STATE
         fi
 
         m=$((n+l))
-        if $m -ge $max
+        if test $m -ge $max
         then
                 m=$max
         fi
@@ -125,8 +126,13 @@ scroll() { # scroll nlines -- MUTATES GLOBAL STATE
 
 ctty() { # ctty
         ## Get the controlling TTY interface.
-        tty <&2 || # only works if not redirecting stderr
+        if test -t 2
+        then
+                # only works if not redirecting stderr
+                tty <&2
+        else
                 echo /proc/self/fd/1 # probably only works on linux
+        fi
 }
 
 winch() {