How can I grep the results of FIND using -EXEC and still output to a file?

Question

Better to explain on examples.

I can:

find . -name "*.py" -type f > output.txt

But how can I store the output to the same file for:

find . -name "*.py" -type f -exec grep "something" {} \

I can't just do

find . -name "*.py" -type f -exec grep "something" {} \ > output.txt

Answer 1

If I understand you correctly this is what you want to do:

find . -name '*.py' -print0 | xargs -0 grep 'something' > output.txt

Find all files with extension .py, grep only rows that contain something and save the rows in output.txt. If the output.txt file exists, it will be truncated, otherwise it will be created.

Using -exec:

find . -name '*.py' -exec grep 'something' {} \; > output.txt

I'm incorporating Chris Downs comment here: The above command will result in grep being executed as many times as find finds pathnames that passes the given tests (only the single -name test above). However, if you replace the \; with a +, grep is called with multiple pathnames from find (up to a certain limit).

See question Using semicolon (;) vs plus (+) with exec in find for more on the subject.

Answer 2

If you want to save all the matching lines across all files in output.txt, your last command does work, except that you're missing the required ; at the end of the command.

find . -name "*.py" -type f -exec grep "something" {} \; > output.txt

If you want each run of grep to produce output to a different file, run a shell to compute the output file name and perform the redirection.

find . -name "*.py" -type f -exec sh -c 'grep "something" <"$0" >"$0.txt"' {} \;

Answer 3

For the record, GNU grep has --include and --exclude arguments that you can use to filter the files it searches:

grep -r --include="*.py" "something" > output.txt

Answer 4

Use tee:

find . -name '*.py' | tee output.txt | xargs grep 'something'

The caveat, is if you have any files with special characters (including spaces) that xargs and grep won't work well with (a file.txt will be interpreted as two files, a and file.txt). The alternative to that is to use either the -x or -print0, but either of those will pollute your output.txt. The -x will use \ to escape certain special characters and this will be in output.txt. The -print0 will use a null byte as a field separator (which also requires xargs -0) and output.txt will look like one long contiguous line of text.

How you deal (or don't) with this is up to you.

Answer 5

You ask:

But how can I store the output to the same file for:

find . -name "*.py" -type f -exec grep "something" {} \

You misunderstand. The reason you can't pipe this to anything is that it is not a full command. The closing \ tells your shell to continue reading the command on the next line, which is not what you intend to do here. When you try:

find . -name "*.py" -type f -exec grep "something" {} \ > output.txt

the \ escapes a blank character that, as a result, will be passed as an extra argument to find, and find will complain that the command passed to its -exec option isn't being terminated.

Terminating that command must be done by adding a + or ; token, and the ; token is special to the shell, so it must be escaped or quoted. Additionally, { and } are also special in most shells, so they must be escaped or quoted as well:

find . -name "*.py" -type f -exec grep "something" \{} \;

or

find . -name "*.py" -type f -exec grep "something" '{}' ';'

These are valid commands, so you can redirect and pipe their output just fine:

find . -name "*.py" -type f -exec grep "something" \{} \; > output.txt
find . -name "*.py" -type f -exec grep "something" '{}' + | fgrep -v notthesefiles: > output.txt

By the way, I prefer to single-quote arguments if I don't want the shell to interpret any characters in them, even though (as @Kusalananda points out), that is not necessary in this case:

find . -name '*.py' -type f -exec grep 'something' \{} \; > output.txt

For the difference between ; and +, try man find.

Answer 6

grep -n CThread '`find . -name "*.cpp"`'

Answer 7

To find files in a directory and search for a string in the result: find $dir -name "*partoffilename*" | xargs -I '{}' grep -ri $searchstring {}