UNIX for Dummies Questions & Answers

There is a requirement that i need to replaced a pattern by another pattern in all the files in my entire file system. there are 1000s of file in the system. let the pattern is "calcuta". i have to replace this pattern by "kolkata" in all those files which contain "calcuta".

I am only able to find out all those list file in the entire file system which contain the pattern using the command.

Code:

find / -type f | xargs grep -il "calcuta"

and usind vi i can do the job. but it is very lengthy process. everytime i have open file to replace the pattern.

can anybody please help me how i can easily do the job? is it possible to do it in sinle command line. is there any extension that i tried to do the rest?

If your sed supports the -i option, it can do the replacement in-place. Otherwise you will need a small script which writes to a temporary file and then replaces the original file with that.

Code:

find / -type f | xargs sed -i 's/calcuta/kolkata/g'

The sed manual page is probably not a good place to start learning, but any decent Unix tutorial or book will have a section about sed.

Or try this:

Code:

find . -type f  | while read files
  do
     echo "$(awk '{gsub(/calcuta/,"kolkata")}1' "$files")" > "$files"
  done

Tested on a number of files about 1Mb in size.

What's the echo for? Why not just

Code:

awk '{ gsub(/calculta/, "kolkata) }1' "$files" >"$files"

... within the same while loop?

In particular, echo on some systems does a fair amount of backslash parsing etc, which will cause undesired changes in the output.

Because going that way :

Code:

awk ...       "$files" > "$files"

the files will get completely emptied out. Just test it and see it for yourself.

While the command was written quickly, I agree it's not the best solution. Anyway, with proper quoting on the files that I tested, I got the results that I expected.

Ah yes, of course. You could also simply use a temporary file, or wiggle with redirection.

Code:

find / -type f | while read files
 do
  awk -v a="$files" '{ gsub(/calcuta/,"kolkata") ; print > a".tmp" }' "$files"
  mv "$files".tmp "$files" 
 done

or

Code:

find / -type f | xargs -i awk -v a='{}' '{ gsub(/calcuta/,"kolkata"); print > a".tmp" } END{print "mv", a".tmp", a }' '{}' | sh

Tested on Ubuntu and BSD.