I've been a fan of fpp (Facebook PathPicker) since I first heard about it. I had long been looking for something like this and had even considered writing it myself. Fortunately someone else spared me the work and did a much better job than I would have.
It's no exaggeration to say that I use this utility every day at $work. In fact I use it many times per hour. It's part of my normal workflow now. For example, I like to pipe the output of git status to fpp and then pick and choose some unit tests I've edited and then run them. I may need to do this many times over the course of a day. The problem is that fpp doesn't have a proper built in history. Having to go through this process of picking through the output of a git status many times per day is a bit of a time sink. It's still maybe faster than what I would have done before, but it feels like jumping through hoops. I want to be able to replay any command I've just run. It should be easy, right?
As it happens, there's already a file which fpp creates after each run. It's found in ~/.fpp/.fpp.sh and it's executable. So, my first attempt at solving this problem was to add a shell alias: alias redo='sh ~/.fpp/.fpp.sh'. This lets me re-run the _very last_ command which I've just run via fpp. I now have instant replay.
However, if I've used fpp for something else in the meantime, the results of that command replace whatever was in ~/.fpp/.fpp.sh. I can't magically get back to the penultimate command which I ran, since it's now lost forever. After playing with this for a few hours, I realized that I really do need to be able to replay my entire history, since I want to be able to pick an arbitrary command and re-run it. Having to remember exactly what I did last before running redo was getting to be frustrating.
As part of the process, I found an open Github issue for fpp history. After I commented it on it, @pcottle made the following very helpful suggestion, which was to alias fpp and wrap it with my own history logic. That seemed like a good idea. So let's look at what we have to work with.
On my machines, ~/.fpp/.fpp.sh generally looks something like this, where the _second last_ line in the file contains the line which I want to re-execute. (There's a blank line which starts the file, but my syntax highlighter seems to be stripping it away here).
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vim -O './README.md' exit; |
I figured I could pretty easily grab this line from ~/.fpp/.fpp.sh and log it to my own history file. I'd then add a little functionality to make it all easier to work with. I had thought about doing this in Perl, but just keeping everything in my .bashrc file felt like it was going to be the most portable solution. I didn't want to have to do anything more complicated than updating and sourcing my dot files in order to get this to work.
The code which I came up with does the following:
- Appends the second last line of
~/.fpp/.fpp.shto my own history file every timefppis run - Adds a
--redoflag, which execs the last line of the history file, when there are no accompanying arguments - Adds a
--historyflag which will print the contents of this history file to the screen, with accompanying line numbers - Execs an arbitrary line from the history file if
--redois supplied with a positive integer. (The integers correspond to the line numbers provided byfpp --history). So,fpp --redo 10execs line 10 fromfpp --history. It's a bit like!10to get to command 10 after runninghistoryin your shell. - Execs an abitrary line from the history file (moving backwards) if
--redois supplied with a negative integer. iefpp --redo -1execs the last line in the file.fpp --redo -2execs the second last line etc
I'm not by any stretch an expert in shell scripting, so I did a lot of searching on StackOverflow, copy/pasting and bugging my colleagues at $work. Eventually and quite happily I've come up with an incantation which suits my needs.
This is what I added to my .bashrc. Usage is contained inline, in the comments.
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function fpp() { local fpp=$(type -fp fpp) HISTORY_FILE="$HOME/.fpp/.fpp_history" FPP_CACHE="$HOME/.fpp/.fpp.sh" touch $HISTORY_FILE # fpp --history just displays entire history prefixed by line numbers # fpp --redo will re-exec the last entry in the history file # fpp --redo -1 will also re-exec the last entry in the history file # fpp --redo -2 will re-exec the second last line in the history file # fpp --redo 11 will re-exec entry number 11 in the history file case "$1" in --history) cat -n $HISTORY_FILE return 1 ;; --redo) if [ $2 ] ; then if [ $2 \> 0 ] ; then LAST_HISTORY_LINE=$(head -n $2 $HISTORY_FILE |tail -n 1) else LINE_NUMBER=$(( $2 * -1)) LAST_HISTORY_LINE=$(tail -n $LINE_NUMBER $HISTORY_FILE | head -n 1) fi else LAST_HISTORY_LINE=$(tail -n 1 $HISTORY_FILE ) fi eval $LAST_HISTORY_LINE return 1 ;; esac LAST_HISTORY_LINE=$(tail -n 1 $HISTORY_FILE) LAST_COMMAND=$(tail -n 2 $FPP_CACHE | head -n 1) # Don't keep adding the same command to the history file. # Also, don't log a message about a no-op. if [[ ("$LAST_COMMAND" != 'echo "nothing to do!" && exit 1') && ("$LAST_COMMAND" != "$LAST_HISTORY_LINE") ]] ; then echo $LAST_COMMAND >> $HISTORY_FILE fi } |
This will get out of date over time, so the canonical version should always be found in my dot-files repo.
If you'd like to see something like this built into fpp itself, it wouldn't hurt to bump the issue I mentioned above. I hope someone finds this helpful.