From 34efed027ac7f859093b8bea32765817222dc2d4 Mon Sep 17 00:00:00 2001 From: Ian Wienand Date: Tue, 17 May 2016 15:43:34 +1000 Subject: [PATCH] Add PS4 to show file/function/line in debug output For something fairly simple, I went back-and-forward with this a bit. Firstly, I realise calling readlink constantly sucks. Due to the way we call dib and source various files, you end up with the source-file from "caller" being usually a very ugly path including levels of "../" indirection. Cleaning this up to something canonical is the only sane way to present it. Because we evaluate _ps4() from a sub-shell in the PS4 string, there's no way for it to do something like build a global in-memory cache in an associative array or similar. It could write out a temp file or some other side-band method, but the overheads of managing this don't seem any different to just calling readlink. If anyone can think of a bash-hack around this that doesn't involve a fork() I'm interested. We could potentially strip some of the leading paths in the assumption you know what they are; but it gets complex when things are split across /usr/bin & /usr/lib and external elements, etc. I thought about arbitrarily shortening it (e.g. just take last 20 characters) which gives you enough of an idea of the file, but looks a bit ugly. Or we could just leave the file-name out all together and assume the function name is unique enough; this also seemed a bit ugly. Obviously it's a matter of taste in the output. It is certainly wider, but it also adds a lot of information. It also makes it fairly clear where there are things we can make less verbose, e.g. I1e39822f218dc0322e2490a770f3dc867a55802c disables tracing in run-parts which is just noise. There's a few other frequently used loops that we could disable tracing for by default to benefit signal:noise. tl;dr : take a look at the logs. I think it is a step in the right direction of making the logs more usable for debugging. Change-Id: I8054a3050415fcb527baeb7012bf133e5c864bf3 --- bin/disk-image-create | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/bin/disk-image-create b/bin/disk-image-create index fb40ec1e..ed8ba62a 100755 --- a/bin/disk-image-create +++ b/bin/disk-image-create @@ -216,6 +216,17 @@ if [ "$CLEAR_ENV" = "1" -a "$HOME" != "" ]; then exec -c $0 "$@" fi + +# Display the current file/function/line in the debug output +function _ps4 { + IFS=" " called=($(caller 0)) + local f=$(readlink -f ${called[2]}) + printf "%-80s " "$f:${called[1]}:${called[0]}" +} +export -f _ps4 +export PS4='+ $(_ps4): ' + + source $_LIB/img-defaults source $_LIB/common-functions source $_LIB/img-functions