Using grep and sed to find and replace a string

You can use find and -exec directly into sed rather than first locating oldstr with grep. It's maybe a bit less efficient, but that might not be important. This way, the sed replacement is executed over all files listed by find, but if oldstr isn't there it obviously won't operate on it.

find /path -type f -exec sed -i 's/oldstr/newstr/g' {} \;

Your solution is ok. only try it in this way:

files=$(grep -rl oldstr path) && echo $files | xargs sed....

so execute the xargs only when grep return 0, e.g. when found the string in some files.

I have taken Vlad's idea and changed it a little bit. Instead of

grep -rl oldstr path | xargs sed -i 's/oldstr/newstr/g' /dev/null

Which yields

sed: couldn't edit /dev/null: not a regular file

I'm doing in 3 different connections to the remote server

touch deleteme
grep -rl oldstr path | xargs sed -i 's/oldstr/newstr/g' ./deleteme
rm deleteme

Although this is less elegant and requires 2 more connections to the server (maybe there's a way to do it all in one line) it does the job efficiently as well