[ILUG] Renaming a lot of files

[Michael Conry]

On Wed, 24 Nov 2004 18:38:23 +0000, Proinnsias Breathnach
<proinnsias at linux.ie> wrote:
> On Wed, Nov 24, 2004 at 06:21:50PM -0000, Tanney, Austin wrote:
> > The naming system is as follows (this is an example filename that actually exists)
> > RDCR011_D09_2004-03-30.scf
> >
> > In this case.. I want to change the name to
> > xRDCR011_D09.scf
> >
> > Basically.. I want to remove the characters "_2004-03-30"
> > Now.. these are not set characters and change for each file.
> > I'm happy enough to run this as 4 processes.. i.e., one for each file type.
> >  
> Okay - are the filenames all the same length ?
> if so - cut may be your friend here !

Or one could do a regexp pattern match using sed to rub out the date:
for x in *scf; do mv $x $(echo $x | sed  -e
"s/_[0-9]\{4\}\-[0-9]\{2\}\-[0-9]\{2\}\././g" -); done
for 5000 files, on an aged PII-450 this took just shy of 3 minutes

Or _much_ better, use Brian Brazil's method (I saw his mail while
I was writing this response).  On the same system, his method  takes a
MUCH nicer 16 seconds to rename 5000 files, better than an order of
magnitude faster :-)

Proinnsias's solution:
> 
> for i in *
> do
>         export $start =`( echo $i | cut -c1-11)`
>         export $end = `(echo $i | cut -c22-25)`
> 
>         mv $i ${start}${end}
> 
> done
renamed the 5000 files in a time of  2minutes and 11 seconds, as he says:
> It's not going to be the fastest - but it'll work :)
Well, it's not the slowest either... though it's a bit less general
than my cut at the problem (I half-heartedly console myself :-).

Brian's method means that the whole collection of 185000 would take
about 10 minutes to
process (based on the unlikely assumption the files are being renamed
on an ancient PII).  A nice illustration of the benefit of using the
right tool for the job

Michael