Friday, 15 April 2011

git import

I had a set of old files with the correct timestamp on, relating to separate versions of a file, ie, foo_16.c, foo_17.c, ... foo_22.c which I wanted to import into a new git repo while preserving the author history

so, this little snippet of code worked - may be useful for others

$ git init
$ git add -N foo.c
$ for i in `seq 16 22` ; do
cp -p hist/foo_$i.c foo.c;
GIT_COMMITTER_DATE="`date -R -r foo.c`" git commit \
--author "Fred Bloggs <>" \
--date="`date -R -r foo.c`" -m "Version $i" foo.c

which you can then branch and commit as normal with current changes

Yes I could probably have done GIT_AUTHOR_DATE=$GIT_COMMITTER_DATE but well, 2 calls to date wasn't that much of an overhead in this case.

anyway, for those that care, the result is up on github

Monday, 4 April 2011

Bash, PS1, PROMPT_COMMAND and other fun

I've just spent 30 mins trying to understand the flow between the various files that set a bash prompt on fedora to do the following: (assumption is here that you're in a colour xterm)

I want:
* my username to change colour depending if I still have a valid kerberos token
* the hostname of the machine I'm on to be in RED if I'm root
* displayed path to be as simple as possible
* $ if I'm a minion, # if root as mormal
* command line editing to work sensibly, no wierdisms on wrapping long lines

so - I used to have on my machine something like the following:
if [ "$PS1" != "" ] ; then
klist -s
if [ $? -eq 0 ] ; then
PS1='\[\033[32m\]\u@\h\[\033[0m\]:\w\$ '
PS1='\[\033[36m\]\u\[\033[32m\]@\h\[\033[0m\]:\w\$ '

and something similar for root.

But on my laptop (F14) I wanted it system wide, so went down the approach of customising /etc/bashrc where you find calls to

1) /etc/sysconfig/bash-prompt-* aren't included, so you're on your own
2) It must point to an executable script that is run every time before displaying the prompt
3) PS1 is still displayed *AND* if you use tab completion / ctrl-l, its *only* PS1 thats displayed on your screen, not the output from PROMPT_COMMAND

so: DON'T do the following:

cat /etc/sysconfig/bash-prompt-xterm
#!/usr/bin/env bash
# set green username if we have a valid kerberos token, else cyan
klist -s
if [ $? -eq 0 ] ; then
# set hostname in red if we're root, green otherwise
if [ ${USER} = 'root' ] ; then

printf "^[%s%s^[[37m@^[%s%s^[[0m:%s " ${K} ${USER} ${U} ${HOSTNAME%%.*} "${PWD/#$HOME/~}"
#echo -ne "\033]0;${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~}\007"
(where ^[ is 'ctrl-v, esc' in vim)
because you end up with stuff like

aelwell@pcitgtelwell:~[aelwell@pcitgtelwell ~]$

until you press ctrl-l and end up with just
[aelwell@pcitgtelwell ~]$ (ie, $PS1)

but *DO* make the call to see if you have a valid token and set the xterm titlebar in /etc/sysconfig/bash-prompt-xterm, but if you're altering PS1, then do so in the traditional places of /etc/bashrc and (as suggested in that file) a custom modification shell script in /etc/profile.d/ directory.

Ho Hum. Hope this clears up for anyone else trying to work out what the sysconfig/bash-prompt-* files do.

oh, and does anyone know a lighter call to see if a token is still valid than 'klist -s'?

Friday, 1 April 2011

Daily WTF Candiate

(Credit for spotting this one goes over to the fine folks at scotgrid who were bitten by the fallout.

Anyway, Useless Use of Cat^H^H^HMore award goes to

Overlaying SLURM job timings on Grafana plots

As you may have noticed, I'm quite fond of Grafana and use it at home and work. One of the dashboards I have at work is the general sta...