Improved signal handling, removing result ISO if xorriso exits with error, redirected a few messages from stdout to stderr

test/merge_debian_isos

@@ -32,6 +32,8 @@ usage() {
   echo "Exported non-empty variable MERGE_FOR_DIST enforces the use of a" >&2
   echo "particular directory in /dists of iso1. Normally only one" >&2
   echo "such directory is found and thus no need to set MERGE_FOR_DIST." >&2
+  echo "Exported non-empty variable MERGE_KEEP_ISO prevents the removal" >&2
+  echo "of result_iso after xorriso indicated failure of production." >&2
   echo "Exported non-empty variable XORRISO overrides command xorriso." >&2
   echo "This may be needed if installed xorriso is older than 1.4.2." >&2
   echo 'If XORRISO is set to "dummy" then no new ISO will emerge.' >&2
@@ -82,39 +84,34 @@ check_single_word() {
 MOUNT_LIST=
 UMOUNT_LIST=
 RMDIR_LIST=
-TEMPFILE_LIST="merged_dists merged_md5sum.txt merged_README.txt temp_file"
+TEMPFILE_LIST=
+EMERGING_ISO=
 
-finish_cleanup() {
+# Cleanup temporary files, mount points and made directories
-  if test -n "$1"
+
+cleanup_ignore_counter=0
+
+cleanup_ignore_handler() {
+  cleanup_ignore_counter=$(expr "$cleanup_ignore_counter" + 1)
+  if test "$cleanup_ignore_counter" -ge 4
   then
-    echo >&2
+    # Reset traps to default
-    if test "$1" -gt 0
+    trap - INT TERM QUIT
-    then
+    echo "--- Ignored several INT, TERM, or QUIT signals during cleanup." >&2
-      echo "--- Merge run aborted !" >&2
+    echo "--- Will give in to next signal." >&2
-    else
+    return 0
-      echo "Merge run ended with success indication." >&2
-    fi
-    exit "$1" 
   fi
+  echo "--- Ignored INT, TERM, or QUIT signal during cleanup." >&2
   return 0
 }
 
-# Cleanup temporary files, mount points and made directories
+cleanup() {
-cleanup_ran=0
 
-cleanup_and_end() {
+  # Make sure to be in cleanup state of traps
-  # Remove trap
+  trap cleanup_ignore_handler INT TERM QUIT
-  trap - INT TERM QUIT EXIT
-
-  if test "$cleanup_ran" = 1
-  then
-    finish_cleanup "$1"
-    return 0
-  fi
-  cleanup_ran=1
 
   echo >&2
-  echo "Cleaning up temporary files and mount points ..." 2>&1
+  echo "Cleaning up temporary files and mount points ..." >&2
 
   ret=0
 
@@ -153,6 +150,28 @@ cleanup_and_end() {
       ret=1
     fi
   done
+
+  if test -n "$EMERGING_ISO" && test -e "$EMERGING_ISO"
+  then
+    if test -n "$MERGE_KEEP_ISO"
+    then
+      echo "Removal of incomplete result ISO suppressed by MERGE_KEEP_ISO." >&2
+      echo "Remaining:  $EMERGING_ISO" >&2
+    else
+      echo "Removing incomplete result ISO." >&2
+      echo \
+ "  (This can be suppressed by exporting non-empty variable MERGE_KEEP_ISO.)" \
+           >&2
+      if rm "$EMERGING_ISO"
+      then
+        dummy=dummy
+      else
+        echo "--- Note: Cannot remove incomplete result: $EMERGING_ISO" >&2
+        ret=1
+      fi
+    fi
+  fi
+
   if test "$ret" = 0
   then
     echo "Cleanup completed." >&2
@@ -160,14 +179,49 @@ cleanup_and_end() {
     echo "--- Cleanup could not be fully completed." >&2
   fi
 
-  # Might exit
+  # Do not come back via trap again
-  finish_cleanup "$1"
+  trap - INT TERM QUIT
-
   return $ret
 }
 
+# Handler for INT TERM QUIT events if "$1" is empty
+# Procedural program exit if "$1" is not empty
+cleanup_and_end() {
 
-# +++ No cleanup_and_end before TEMPFILE_LIST is verified to be missing +++
+  # Early assume cleanup state of traps
+  trap cleanup_ignore_handler INT TERM QUIT
+  trap - EXIT
+
+  if test -z "$1"
+  then
+    exit_value=6
+    echo >&2
+    echo "--- Encountered INT, TERM, or QUIT signal." >&2
+  else
+    exit_value="$1"
+  fi
+  cleanup
+  echo >&2
+  if test "$exit_value" -gt 0
+  then
+    echo "--- Merge run aborted !" >&2
+  else
+    echo "Merge run ended with success indication." >&2
+  fi
+  exit "$exit_value" 
+}
+
+# Handler for rogue EXIT
+cleanup_for_exit() {
+
+  # Early assume cleanup state of traps
+  trap cleanup_ignore_handler INT TERM QUIT
+  trap - EXIT
+
+  cleanup
+  echo >&2
+  echo "--- Merge run ended by unexpected EXIT event !" >&2
+}
 
 
 ## Check arguments and dependencies
@@ -191,7 +245,7 @@ do
   then
     dummy=dummy
   else
-    echo "--- Missing a helper program: $i" 2>&1
+    echo "--- Missing a helper program: $i" >&2
     missing=1
   fi
 done
@@ -210,16 +264,16 @@ then
     dummy=dummy
   else
     echo '--- Help text of xorriso program '"$XORRISO"' lacks word "replay".' \
-         2>&1
+         >&2
-    echo "--- It will fail when trying to make the new ISO bootable." 2>&1
+    echo "--- It will fail when trying to make the new ISO bootable." >&2
-    echo "    Consider to get and compile GNU xorriso from" 2>&1
+    echo "    Consider to get and compile GNU xorriso from" >&2
-    echo "      https://www.gnu.org/software/xorriso" 2>&1
+    echo "      https://www.gnu.org/software/xorriso" >&2
-    echo "    and to export variable XORRISO with the binary's path." 2>&1
+    echo "    and to export variable XORRISO with the binary's path." >&2
     echo >&2
     missing=1
   fi
 else
-  echo "--- Test run of xorriso program failed: $XORRISO -no_rc -version" 2>&1
+  echo "--- Test run of xorriso program failed: $XORRISO -no_rc -version" >&2
   missing=1
 fi
 if test "$missing" = 1
@@ -229,11 +283,13 @@ then
 fi
 
 existing_tempfiles=
-for i in $TEMPFILE_LIST
+for i in merged_dists merged_md5sum.txt merged_README.txt temp_file
 do
   if test -e "$i"
   then
     existing_tempfiles="$existing_tempfiles $i"
+  else
+    TEMPFILE_LIST="$TEMPFILE_LIST $i"
   fi
 done
 if test -n "$existing_tempfiles"
@@ -245,8 +301,12 @@ then
   exit 1
 fi
 
+
 # +++ From here on: Always call cleanup_and_end to perform exit +++
-trap cleanup_and_end INT TERM QUIT EXIT
+
+
+trap cleanup_and_end INT TERM QUIT
+trap cleanup_for_exit EXIT
 
 RESULT_ISO="$1"
 check_single_word "$2" "result_iso" || cleanup_and_end 1
@@ -683,6 +743,9 @@ else
 fi
 echo >&2
 
+# Mark the result path for possible removal by cleanup
+EMERGING_ISO="$RESULT_ISO"
+
 if "$XORRISO" \
   -no_rc \
   -indev "$iso_1" \
@@ -700,6 +763,9 @@ if "$XORRISO" \
   -padding included \
   -compliance no_emul_toc
 then
+  # Revoke mark for possible removal by cleanup
+  EMERGING_ISO=
+
   test "$XORRISO" = echo || \
     echo "Run of xorriso program ended without error indication." >&2
 else