Multiple search and replace actions in one large text file

Solution 1:

I would use sed like this :

sed -i "s/www\.abcdef/www.test.abcdef/g;s/www\.kmlnop/www.test.klmnop/g;" yourfile.txt

-i option stands for "in place" replacement. You can tell sed to create a backup of your file providing an extension to this option ( -i.bak will backup yourfile.txt as yourfile.txt.bak ).

Solution 2:

If you have many more search patterns, you could save them in a file and read the substitutions from there. For example, say these are the contents of replacements.txt:

www\.abcdef www.test.abcdef 
www\.klmnop www.test.klmnop

You can then read a list of N replacements and replace them with this:

while read from to; do
  sed -i "s/$from/$to/" infile.txt ; 
done < replacements.txt 

NOTES:

• This assumes your search strings do not contain spaces and any strange characters need to be escaped in replacements.txt.
• It will run one sed per replacement which may take a while if you have many replacement operations.
• It can deal with an arbitrary number of replacements (thousands or millions or whatever) as long as you don't mind that it will take a bit more time.

Another option would be to write the above as a sed script:

s/www\.abcdef/www\.test\.abcdef/g;
s/www\.kmlnop/www\.test\.klmnop/g;
s/aaaa/bbbb/g;
s/cccc/dddd/g;
s/eeee/ffff/g;

You can then run the script on your file and it will make all the replacements in one go:

sed -f replace.sed infile.txt