Optimizing find with many replacements


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# 1  
Optimizing find with many replacements

Hello,

I'm looking for advice on how to optimize this bash script, currently i use the shotgun approach to avoid file io/buffering problems of forks trying to write simultaneously to the same file. i'd like to keep this as a fairly portable bash script rather than writing a C routine.

in a nutshell, there are many conditions in a file that i'm looking to replace strings. any particular file may have some, none or all of the requirements to replace a string.

currently

Code:
Longstring='lots of stuff'
spushd $HOME/somepath

gfind . -depth -name "somefile" -type f -writable -exec gsed -i '1{/^#./! s/.*/'"$Longstring"'/}' {} \;
  gfind . -depth -name "somefile" -type f -writable -exec gsed -i -r 's/ts=4/ts=2/g' {} \;
  gfind . -depth -name "somefile" -type f -writable -exec gsed -i -r 's/sw=4/sw=2/g' {} \;
  gfind . -depth -name "somefile" -type f -writable -exec gsed -i -r 's/tab-width: 4/tab-width: 2/g' {} \;
  gfind . -depth -name "somefile" -type f -writable -exec gsed -i -r 's/mode: tcl/mode: _tcl/g' {} \;
  gfind . -depth -name "somefile" -type f -writable -exec gsed -i -r 's/c-basic-offset: 4/c-basic-offset: 2/g' {} \;
  gfind . -depth -name "somefile" -type f -writable -exec gsed -i -r 's/^\s*(size.*)$/\1/g' {} \;
  gfind . -depth -name "somefile" -type f -writable -exec gsed -i -r 's/^\s*(md.*)$/\1/g' {} \;
  gfind . -depth -name "somefile" -type f -writable -exec gsed -i -r 's/^\s*(rmd.*)$/\1/g' {} \;
  gfind . -depth -name "somefile" -type f -writable -exec gsed -i -r 's/^\s*(sha.*)$/\1/g' {} \;
  gfind . -depth -name "somefile" -type f -writable -exec gsed -i -r 's/^(python.versions.*)$/python.versions 27 36/g' {} \;
  spopd

as you can see, these operations are sequential which can take quite a while.

should i modify the find to do depth first?

can i fork the find and avoid file io problems?

spawn different processes?

thanks
# 2  
Just to be clear, is it true that you want the output of the sed from the 1st find to be written to standard output (and not be included in the changes made to updated files) while all of the other finds run seds that will make updates to the files and not write anything to standard outputa?

Why not run all of the sed commands in the last 10 invocations of sed in a single invocation of find -execing sed?

And, why not use two -execs in a single invocation of find instead of invoking find eleven times?
This User Gave Thanks to Don Cragun For This Post:
# 3  
Quote:
Originally Posted by Don Cragun
Just to be clear, is it true that you want the output of the sed from the 1st find to be written to standard output (and not be included in the changes made to updated files) while all of the other finds run seds that will make updates to the files and not write anything to standard outputa?

Why not run all of the sed commands in the last 10 invocations of sed in a single invocation of find -execing sed?

And, why not use two -execs in a single invocation of find instead of invoking find eleven times?
Thanks for help.

All of the sed is basically a large 'OR' boolean.

Any particular file, could have any sed condition, 1..."#conditions", so the the sed needs to search for a condition in the file before moving on to the next file.

Basically, the script has expanded over time and now it's getting to the point where I'd like to refactor it.

That is sort of the question, is it more efficient to let find search a massive amount of files and let sed chew on one condition at a time? Which it does now, which is basically unrolling the loops in your suggestion about concatening the sed to two exec commands?

or as you suggest, find pauses its search while let sed grind on one file searching all the conditions at once?

Say average files to search is ~ 100,000 files, average size ~40k/~100k

Thanks for the thoughts.

Last edited by f77hack; 04-16-2018 at 05:47 PM.. Reason: typos
# 4  
I think what Don is trying to tell you is: this command

Code:
gfind . -depth -name "somefile" -type f -writable

will find some list of files. Since it is repeated eleven times it will find (and hence process) eleven times the same list of files.

So you could put all the changes in the different sed-scripts into one sed-script and write something like:

Code:
gfind . -depth -name "somefile" -type f -writable -exec gsed -i -f /some/where/script {} \;

where /some/where/script would contain
Code:
1 {
     /^#./! s/.*/"$Longstring"/
   }
s/ts=4/ts=2/g
s/sw=4/sw=2/g
s/tab-width: 4/tab-width: 2/g
....

I have to admit you would have to work a bit to get the variable "$Longstring" passed properly, but this minor issue aside you should be a lot faster: you recurse the filesystem only once (instead of eleven times) and you call sed only once instead of eleven times for each file.

I hope this helps.

bakunin
This User Gave Thanks to bakunin For This Post:
# 5  
@bakunin yes, this is exactly what i was looking to do.

Thank you.

P.S. How would expand the script if instead of "somefile" but an array of "somefiles=()"? Would you spawn off
Code:
gfind

?

Last edited by f77hack; 04-16-2018 at 08:42 PM.. Reason: add PS
# 6  
Using bash and depending on how big the somefiles[] is (don't want to blow out the command line):

Code:
 gfind . \( -false ${somefiles[@]/#/-o -name } \) -type f ...

This User Gave Thanks to Chubler_XL For This Post:
# 7  
You can still have an embedded sed script.
All shells but (t)csh can have a multiline string
Code:
echo 'two
lines'

So the following should work
Code:
gfind . -depth -name "somefile" -type f -writable -exec gsed -i -r '
    1{/^#./! s/.*/'"$Longstring"'/}
    s/ts=4/ts=2/g
... 
    s/^(python.versions.*)$/python.versions 27 36/g
' {} \;

@Don, not true, -i outputs to file, given in all the sed invocations.
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