DEBUG on tty

_stderr

@@ -1,3 +0,0 @@
-DETECTED0: [This is stderr
-./useless.sh: line 7: nope: unbound variable]
-EXIT 1

_stdout

@@ -1,2 +0,0 @@
-stdout A
-stdout B

bin/bash-strict2.sh

@@ -0,0 +1,52 @@
+#!/bin/bash
+
+# CONSTANTS
+DEBUG=true
+TMP_ERROR=$(mktemp -t "$(basename $0).XXXXXXXX" --tmpdir=/run/user/$(id -u))
+SCRIPT=$1
+
+# FUNCTIONS
+
+function exit {
+  code=${1:-0}
+
+  # a bit of magic: read content of file still on write!
+  # count=$(wc -c $TMP_ERROR | cut -d' ' -f1)
+  # content=$(head -qc$count $TMP_ERROR)
+
+  if [[ -s $TMP_ERROR ]]; then
+    content=$(<$TMP_ERROR)
+    $DEBUG && >/dev/tty echo '---stderr---'
+    >&4 echo "DETECTED: [$content]"
+  fi
+  cleanup ${code}
+}
+
+function success {
+  if [[ -s $TMP_ERROR ]]; then
+    $DEBUG && >/dev/tty echo '---stderr---'
+    >&2 cat $TMP_ERROR
+  fi
+  cleanup 0
+}
+
+function cleanup {
+  code=${1:-0}
+  $DEBUG && >/dev/tty echo "---exit $1---"
+  trap - ERR TERM INT EXIT
+  rm $TMP_ERROR
+  builtin exit $code
+}
+
+# MAIN
+
+set -TEue -o pipefail
+trap 'exit $?' ERR TERM INT EXIT
+# export -f exit
+
+# magic FD
+exec 3>$TMP_ERROR 4>/dev/stderr
+$DEBUG && >/dev/tty echo '---stdout---'
+source $SCRIPT 2>&3
+exec 3>&- 4>&-
+success

stderr

@@ -1,2 +0,0 @@
-This is stderr
-./useless.sh: line 7: nope: unbound variable

useless.sh

@@ -2,9 +2,10 @@
 
 echo "stdout A"
 # echo toto >>/tmp/toto
+# $nope
+# exit 6
 >&2 echo "This is stderr"
 echo "stdout B"
-$nope
 echo "stdout C"
-# command_not_found
+command_not_found
 echo END of useless