SED command

echo 1_2_spell.xml | sed 's/\([^\_]*\)\_\([^\_]*\)\_\([^\_\.]*\)\.xml/\1.\2\_\3\.xml/'


seems to work

Not sure what you are trying to do here?

But this works:

echo 1_2_spell.xml | sed 's/_/\1./'

...perhaps a more comprehensive example of the stream and manipulation required would be helpful?...or are we going for an obfusication award?

..or even:

echo 1_2_spell.xml | sed 's/_/./'

as long as you don't stipulat the g (global obtion, only the first _ will be substituted!

How can I make a check in the characters between the "_" to be numeric?

For exp:

1_2_spell.xml convert 1.2_spell.xml

but for

1700_command_spell.xml (ignore: dun convert as "command" is non numeric)

Thanks.

check for numeric as  

[0-9]+

echo 12.34_Abc.xml
echo 12.34_Abc.xml | sed -e 's/\([0-9]\+\)\.\([0-9]\+\)_\([^0-9]\+\)\.xml/\1_\2.\3.xml/'

It gives :

12_34.Abc.xml

I need:

12.34_Abc.xml

Please advise.

Thanks.
CM

I would have thought that my solution and that of avizit also did what was required. The check for numbers was an additional insight.

Anyway - your call:)