working FD3+4

_stderr

@@ -0,0 +1,3 @@
+DETECTED0: [This is stderr
+./useless.sh: line 9: command_not_found: command not found]
+ON_EXIT2 127

_stdout

@@ -0,0 +1,3 @@
+stdout A
+stdout B
+stdout C

bin/bash-strict

@@ -8,13 +8,14 @@ TMP_ERROR=$(mktemp -t "$(basename $0).XXXXXXXX" --tmpdir=/run/user/$(id -u))
 
 function exit {
   code=${1:-0}
+  echo
+  echo "ERROR #${code} due to:"
 
   stack_lines=("${BASH_LINENO[@]}")
   stack_functions=("${FUNCNAME[@]}")
   stack_sources=("${BASH_SOURCE[@]}")
 
   tmp_error=${2:-/dev/null}
-    echo "ERROR #${code} due to:"
   [[ -s $tmp_error ]] && cat $tmp_error && rm $tmp_error
 
   echo "${stack_lines[@]}"
@@ -39,10 +40,12 @@ for i in "${original_args[@]}"; do quoted_args+=("${i@Q}"); done
 set -TEue -o pipefail
 export -f exit
 # echo PROCESS START
+
 bash $opt_debug -c "
   set -TEue -o pipefail;
   trap 'exit \$? $TMP_ERROR' ERR TERM INT EXIT; 
   source $command ${quoted_args[*]}
   " 3>&1 1>&2 2>&3 | tee $TMP_ERROR
-# echo PROCESS END succesfully
+# TODO: delay the stacktrace message to output to stderr, idea: $TMP_ERROR + $TMP_STACK
 
+# echo PROCESS END succesfully

capture.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+{
+  IFS=$'\n' read -r -d '' CAPTURED_STDERR
+  IFS=$'\n' read -r -d '' CAPTURED_STDOUT
+} < <((printf '\0%s\0' "$(./useless.sh)" 1>&2) 2>&1)
+
+echo 'Here is the captured stdout:'
+echo "${CAPTURED_STDOUT}"
+echo
+
+echo 'And here is the captured stderr:'
+echo "${CAPTURED_STDERR}"
+echo
+
+# function launch {
+#   echo START
+#   bash -c "set -TEue -o pipefail; . ./useless.sh"
+#   echo END
+# }
+#
+# set -TEue -o pipefail
+# stderr=$(launch 3>&1 1>&2 2>&3 | tee /dev/stderr)
+# >&2 echo "ERR: $stderr"
+# # (
+#   echo -n "ERR: "
+#   cat stderr
+# ) >&2
+# >&2 echo 'here is the captured stderr:'
+# >&2 echo "$(<stderr)"
+# >&2 echo

err

@@ -0,0 +1,4 @@
+This is stderr
+./useless.sh: line 6: command_not_found: command not found
+DETECTED [This is stderr
+./useless.sh: line 6: command_not_found: command not found]

stderr

@@ -0,0 +1,2 @@
+This is stderr
+./useless.sh: line 9: command_not_found: command not found

stdout

@@ -0,0 +1,5 @@
+stdout A
+stdout B
+DETECTED3 [This is stderr
+./useless.sh: line 6: nope: unbound variable]
+ON_EXIT 1

test5.sh

@@ -1,10 +1,10 @@
-#!/usr/bin/env -S -- bash-strict
+#!./bin/bash-strict
 
 function f2 {
   # return 6
   # exit 7
-  unknown_command
   echo $nope
+  unknown_command
 }
 
 function f1 {

test7.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+# function launch {
+#   exec 3>&1 1>&2 2>&3 ./useless.sh
+#   exec 3>&1 1>&2 2>&3
+# }
+
+function on_exit {
+  FAILURE=${1:-0}
+  [[ $FAILURE -gt 0 ]] && >&2 echo EXIT "$FAILURE"
+  trap - ERR TERM INT EXIT
+}
+
+export -f on_exit
+{
+  myvar=$(bash -c "
+    set -TEue -o pipefail;
+    trap 'on_exit \$?' ERR TERM INT EXIT
+    . ./useless.sh
+  " 3>&1 1>&2 2>&3 | tee /dev/fd/4 | 3>&5 1>&2 2>&3 tee /dev/fd/5)
+} 5>&1 4>&2 # magic trick: fd4 grabs stderr, then show up again on stderr
+
+echo ----------
+echo -e "stderr is:\n$myvar"

test8.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+
+function on_exit {
+  code=${1:-0}
+  # exec 3>&1 1>&2 2>&3
+  # exec 1>&- 3>&- 2>&-
+  # exec 2> >(tee /dev/stderr)
+  trap - ERR TERM INT EXIT
+  # exec 2>&-
+  # exec 1> >(tee -ap /dev/stdout) 2>&- 3> >(tee -ap /dev/stderr)
+  # exec 2>&- 3>&-
+  # echo CLOSE OPEN PIPE suite
+  count=$(wc -c stderr | cut -d' ' -f1)
+  content=$(head -qc$count stderr)
+  >&4 echo "DETECTED0: [$content]"
+  >&4 echo ON_EXIT2 ${code}
+}
+
+set -TEue -o pipefail
+trap 'on_exit $?' ERR TERM INT EXIT
+# exec 2>stderr 3> >(tee -ap /dev/stderr)
+[[ -f stderr ]] && rm stderr
+# exec 1> >(tee -p /dev/stdout) 2> >(tee stderr | tee -p /dev/stderr) 3> >(tee -p /dev/stderr)
+# exec 2> >(tee stderr | tee -p /dev/stderr) # 3> >(tee -p /dev/stderr)
+# exec 3> >(tee stderr | tee -p /dev/stderr) 2>&3
+# exec 3> >(tee stderr) 2>&3-
+# exec 2> >(tee stderr)
+exec 3>stderr 4>/dev/stderr
+source ./useless.sh 2>&3
+exec 3>&- 4>&-
+>&2 cat stderr
+trap - ERR TERM INT EXIT
+echo --END1
+>&2 echo --END2

useless.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+echo "stdout A"
+# echo toto >>/tmp/toto
+>&2 echo "This is stderr"
+echo "stdout B"
+# $nope
+echo "stdout C"
+command_not_found
+echo END of useless