Extract reclaim_tty into reusable function

Move the inline TTY reclamation logic from build.func into a standalone reclaim_tty() function in core.func. This improves code reusability, as the function now needs to be called before each interactive prompt (not just after install) since pct exec/pull/enter can take the terminal away again. The function also includes better error handling with checks for perl availability and /dev/tty existence, and explicitly sets SIGTTOU to IGNORE in perl.

misc/build.func

@@ -5200,15 +5200,11 @@ EOF
     # TSTP = Ctrl+Z, TTIN = bg read from tty, TTOU = bg write to tty (tostop)
     trap '' TSTP TTIN TTOU
 
-    # lxc-attach takes the controlling terminal while the install runs and does
-    # not hand it back, leaving us in a background process group. Reading from
-    # the terminal then returns EIO instead of blocking, because SIGTTIN is
-    # ignored above - so every recovery prompt fails before the user can answer.
-    # Redirecting to /dev/tty does not help: the rule applies to the terminal,
-    # not the file descriptor. Claim the foreground group back; SIGTTOU is
-    # ignored too, so tcsetpgrp() succeeds instead of stopping us. No-op when we
-    # already are in the foreground. perl is a hard dependency of Proxmox VE.
-    perl -e 'use POSIX; open(my $t, "+<", "/dev/tty") or exit 1; POSIX::tcsetpgrp(fileno($t), getpgrp()) or exit 1;' 2>/dev/null || true
+    # lxc-attach left us in a background process group - claim the terminal back
+    # before we print anything. Note this does NOT hold: the log collection
+    # below uses pct pull/exec, which take it away again, so every interactive
+    # prompt has to reclaim it again right before its read.
+    reclaim_tty
 
     msg_error "Installation failed in container ${CTID} (exit code: ${install_exit_code})"
 
@@ -5338,6 +5334,7 @@ EOF
       pct enter "$CTID"
       echo ""
       echo -en "${YW}Container ${CTID} still running. Remove now? (y/N): ${CL}"
+      reclaim_tty
       if read -r response </dev/tty && [[ "$response" =~ ^[Yy]$ ]]; then
         pct stop "$CTID" &>/dev/null || true
         pct destroy "$CTID" &>/dev/null || true
@@ -5497,6 +5494,7 @@ EOF
 
     local response=""
     local read_rc
+    reclaim_tty
     read -t 60 -r response </dev/tty
     read_rc=$?
     if [[ $read_rc -eq 0 ]]; then
@@ -5761,6 +5759,7 @@ destroy_lxc() {
   trap 'echo; msg_error "Aborted by user (SIGINT/SIGQUIT)"; return 130' INT QUIT
 
   local prompt
+  reclaim_tty
   if ! read -rp "Remove this Container? <y/N> " prompt </dev/tty; then
     # read returns non-zero on Ctrl-D/ESC
     msg_error "Aborted input (Ctrl-D/ESC)"

misc/core.func

@@ -1042,6 +1042,39 @@ ensure_tput() {
   fi
 }
 
+# ------------------------------------------------------------------------------
+# reclaim_tty()
+#
+# - Reclaims the controlling terminal's foreground process group
+# - lxc-attach takes the terminal and does not hand it back, leaving us in a
+#   background process group. Reading from the terminal then returns EIO
+#   instead of blocking, because SIGTTIN is ignored during recovery - so the
+#   prompt fails before the user can answer and their keystroke leaks into the
+#   parent shell. Redirecting to /dev/tty does not help: the rule applies to
+#   the terminal, not to the file descriptor.
+# - pct exec/pull/enter use lxc-attach internally, so the terminal can be taken
+#   away again at any point. Call this immediately before each interactive
+#   read, not once after the install.
+# - SIGTTOU is ignored inside perl so tcsetpgrp() succeeds instead of stopping
+#   us. No-op when we already are in the foreground or there is no terminal.
+#   perl is a hard dependency of Proxmox VE.
+# ------------------------------------------------------------------------------
+reclaim_tty() {
+  command -v perl >/dev/null 2>&1 || return 0
+  [[ -e /dev/tty ]] || return 0
+
+  local pgid
+  pgid=$(ps -o pgid= -p $$ 2>/dev/null | tr -d ' ') || true
+
+  perl -e '
+    use POSIX;
+    $SIG{TTOU} = "IGNORE";
+    my $pgid = $ARGV[0] || POSIX::getpgrp();
+    open(my $t, "+<", "/dev/tty") or exit 1;
+    POSIX::tcsetpgrp(fileno($t), $pgid) or exit 1;
+  ' "${pgid:-0}" 2>/dev/null || true
+}
+
 # ------------------------------------------------------------------------------
 # is_alpine()
 #

misc/error_handler.func

@@ -499,6 +499,7 @@ error_handler() {
 
       local response=""
       local read_rc
+      declare -f reclaim_tty >/dev/null 2>&1 && reclaim_tty
       read -t 60 -r response </dev/tty
       read_rc=$?
       if [[ $read_rc -eq 0 ]]; then