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I have a few git svn related functions that see if I have to pull/push from/to the repository. My problem is that the functions I've wrote to gather these informations are too slow, I'd like to make them async so that PS1 shows a default, if though the data produced by the functions is ready I want it printed.

I'd like to have these information in my prompt so that for example I know if I have to pull, without doing a git svn fetch everytime.

This is the function I call to add a ↑ to my PS1 if I have to push my changes.

function hasToPush {
    (($1 == 0)) && 
        (git svn dcommit --dry-run 2>/dev/null | grep -q "diff-tree" && echo "↑")

This is the functions I call to add a ↓ if I have to pull, the first is used to refresh my index every 2 minutes, so that I can do the (($latest > $current)) check.

function loopingGitSvnFetch {
     sleep 120
     git svn fetch &>/dev/null
loopingGitSvnFetch &
function hasToPull {
    (($1 == 0)) && (
        latest=$(git svn log | awk 'NR==2' | cut -d ' ' -f1 | tr -d 'r')
        (($latest > $current)) && echo "↓"

To make them async I've tried to put them together like this:

function async {
     git diff-index --quiet --cached HEAD &>/dev/null
     dirty=$(echo $?)
     push=$(hasToPush $dirty)
     gitsvn=$(git svn info 2> /dev/null | grep Revision)
     gitsvn=${gitsvn#Revision: }
     pull=$(hastoPull $dirty $gitsvn)
     callback $push $pull
     } &

But that produces the same slow behaviour. I've tried to put results in a file and then read it after, but I don't like the approach. I've thought about using PROMPT_COMMAND but that would not be async, it would be on demand.

Could you shed some light on how PS1 behaves or on what I'm doing wrong? Thank you in advance.

PS: Could someone with 300 rep add the async and ps1 tags?


I added these line to my .bashrc as a simple test, it seemed to work, so having rewrote them (I reverted my previous attempt) seems was a good thing :)

while true;
    discoverScmInfo &>~/.ps1
    sleep 1
done &
PS1='$(customW)$(cat ~/.ps1)\$ '

I'll put this in a function and check if the job is already running before calling it. Sorry about this, after all it seems that all I needed was to write about it. :)

share|improve this question
Regarding tags: async might be useful, but one might usually have either jobs or parallel instead, so we'll see if it catches on. But defnitely not PS1 - it is just a shell configuration variable; you have the prompt tag for what you mean. –  rozcietrzewiacz Nov 23 '11 at 17:46
Thanks for the added tags. –  Alberto Zaccagni Nov 23 '11 at 17:47
Why don't you like the file-based approach? It really seems the only reasonable one to me. Maybe optimizing it would be enough for you - please show, how did you use this approach. –  rozcietrzewiacz Nov 23 '11 at 17:51
While I was coding I thought it would not be such a great idea to start creating dotfiles around my home. I reverted all my changes to bashrc, so now I've reimplemented it and it seems to work ok ^^". Sorry about this. Btw, since this is not a problem anymore, do you have some hints on making this better? –  Alberto Zaccagni Nov 23 '11 at 18:06

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