Please help me, wasted hrs, to find this soulution:-
I need a command that will work on file (xml) and replace multiple occurrence (more than 2 times)

Examples

1. '==='

2. '===='

3. '======='

should be replaced by just '=='
Note :- single character should be replaced. (= should be replaced by ==)

I have used this command:-

sed 's/==*/==/g' example.xml > example.xml

1) <namespace key="109" case="first-letter">Book talk</namespace>
2) st        = ''[[Sleeping Murder]]'' 
| cause       =

1) <namespace key=="109" case=="first-letter">Book talk</namespace>
2) st        == ''[[Sleeping Murder]]'' 
| cause       ==

Seems to me that this is what you wanted, isn't it?

If you only want to replace two or more occurences of "=" use:

sed 's/===*/==/g' example.xml > example.xml.result

Is there any possibility, that after editing original file, and after process completes, can we replace original with output file, Becoz i have a file of 38 Gb.
I have managed shell script, as i am doing shell scripting first time, i am trying to create a script where file should be deleted after completing the process.

I want to extend command and delete original file and name the new file created same as old one.

Ex.

 sed 's/===*/==/g' inputfile.xml > outputfile.xml && COMMAND_FOR_DELETING_OLD_FILE && \
COMMAND_FOR_RENAMING_NEW_FILE_TO_SAME_AS_OLD_FILE

There is no other way than what you have already found out: use a different file and then move the new file over the old file.

The reason for this i have described here and in some other postings too - i don't want to repeat it.

Btw., a suggestion: stay away from GNU-seds "-i" switch: it will just make your script less portable, but will do nothing else than do the "mv"-operation automatically afterwards.

I hope this helps.

bakunin

Hello,

Thank you for your suggestion. I have used, Below command, where it gives output in same file.

perl -i -pe's/===*/==/g' Example.xml

You seem to have misunderstood what i explained. "perl -i" does the same as "sed -i": it creates a temporary second file where it stores the changes and moves this over the original file as the last step.

You gain nothing by using perl (save for a considerably slower speed of execution, because native UNIX commands are way faster).

The point is simple: to edit a file you need to be able to store 2 versions of it.*) There is no way around that. The "-i" options of various tools just blur that fact by hiding this temporary file, but it is still necessary.

If you fear a long execution time for moving the file: don't. It is in fact just a change in the files i-node (which is a few bytes) as long as the temporary file and the original file are on the same filesystem. To execute

mv /path/to/fileA /path/to/fileB

(cat /path/to/file) | sed '<somecommand>' > /path/to/file

That won't work even when there's just a single byte in the file, if the shell first creates the sed portion of the pipeline. There are no guarantees on which component of a pipeline will be created first.

Regards,
Alister