Change multiple files

I'm surprised nobody has mentioned the -exec argument to find, which is intended for this type of use-case, although it will start a process for each matching file name:

find . -type f -name 'xa*' -exec sed -i 's/asd/dsg/g' {} \;

Alternatively, one could use xargs, which will invoke fewer processes:

find . -type f -name 'xa*' | xargs sed -i 's/asd/dsg/g'

Or more simply use the + exec variant instead of ; in find to allow find to provide more than one file per subprocess call:

find . -type f -name 'xa*' -exec sed -i 's/asd/dsg/g' {} +

Better yet:

for i in xa*; do
    sed -i 's/asd/dfg/g' $i
done

because nobody knows how many files are there, and it's easy to break command line limits.

Here's what happens when there are too many files:

# grep -c aaa *
-bash: /bin/grep: Argument list too long
# for i in *; do grep -c aaa $i; done
0
... (output skipped)
#