It's good to have last incorrect comment to correct it, but soon after that, it becomes potentially confusing garbage.
My approach is two-step: store commands that fail when they do, and remove them sometime later.
Store commands that fail when they do:
FAILED_COMMANDS="$(history | tail -1l | cut -c -5) $FAILED_COMMANDS"
trap error_handler ERR
trap command signals executes
command when one of
signals is "raised".
$(command), executes the
command and captures its output.
When command fails, this snippet of code captures history number of last command saved into history, and stores it in variable for future deletion.
Simple, but works incorrectly with
HISTIGNORE – when command is not saved into history due to one of the variables, history number of last command saved into history is previous command's one; so, if incorrect command is not saved into history, previous command is going to be deleted.
Slightly more complicated version, which works correctly in that case:
local LAST_HISTORY_ENTRY=$(history | tail -1l)
# if last command is in history (HISTCONTROL, HISTIGNORE)...
if [ "$LAST_COMMAND" == "$(cut -d ' ' -f 2- <<< $LAST_HISTORY_ENTRY)" ]
# ...prepend it's history number into FAILED_COMMANDS,
# marking the command for deletion.
FAILED_COMMANDS="$(cut -d ' ' -f 1 <<< $LAST_HISTORY_ENTRY) $FAILED_COMMANDS"
trap error_handler ERR
trap debug_handler DEBUG
Remove stored commands sometime later:
for i in $(echo $FAILED_COMMANDS | tr ' ' '\n' | uniq)
history -d $i
trap exit_handler EXIT
When exiting Bash, for each unique history number remove corresponding history entry,
FAILED_COMMANDS to not remove commands which inherited history numbers from already deleted commands.
If you're sure that
FAILED_COMMANDS will be free from duplicates, you can simple iterate over it
for i in $FAILED_COMMANDS). If, however, you expect it to be not sorted from greatest to smallest (in this case it always is), replace
History numbers in
FAILED_COMMANDS must be unique and sorted from greatest to smallest, because when you delete entry, next commands' numbers are shifted – ie. when you issue
history -d 2, 3rd entry becomes 2nd, 4th becomes 3rd, etc.
Because of that, when using this code, you cannot manually call
history -d <n>
n is smaller or equal to greatest number stored in
and expect the code to work properly.
It's probably good idea to hook
EXIT, but you can also call it anytime earlier.