What's wrong with this grep?

Question

> output2.txt
cd # some directory i'm trying to search
find views/shared -type f -name "*.js" -print0 | while IFS= read -r -d $'\0' line; do
    echo -n "${line%.js}" | tee -a ~/Documents/counter/output2.txt
    grep -lr "${line%.js}" . | wc -l | tee -a ~/Documents/counter/output2.txt   # produce a count of occurrences
    regex='[a-zA-Z]+.extend'
    grep -f $line $regex
    grep -lr "${line%.js}" . | tee -a ~/Documents/counter/output2.txt           # produce a list of occurrences
done

Returns

grep: brackets ([ ]) not balanced

All the examples I've seen on the web seem to indicate there is nothing wrong here, so i'm pretty confused

Surely the square brackets are balanced, aren't they?

Solution

Your issue is the -f option. Instead of specifying the file to search, -f specifies a file to read a list of patterns from. OS X grep's man page explains it, though not very clearly:

 -f file, --file=file
         Read one or more newline separated patterns from file.  Empty pattern lines match every input
         line.  Newlines are not considered part of a pattern.  If file is empty, nothing is matched.

The help for GNU grep is actually more straightforward:

$ grep --help | grep -- '-f,'
  -f, --file=FILE           obtain PATTERN from FILE
$ 

This behavior of -f is, according to GNU grep's man page, specified by POSIX.

Your fix is probably to change your line:

grep -f $line $regex

to:

egrep "$regex" -- "$line"

• You are using an extended regular expression so use egrep or grep -E
• The -- will prevent grep from parsing any options in the $line variable, e.g. it would protect you against a file named "-r funnyname.js"

Comments

[Jakuje]

What are you trying to achieve? what is in your file referenced by $line variable? By default grep needs to escape brackets to take into effect, unless you use extended grep

[itsmichaelwang]

I put the full command. I'm grepping through a BackboneJS code base and looking for the phrase "*.extends" to find parent classes

[itsmichaelwang]

The brackets are for range selection

[Jakuje]

@drewbenn is right. You are using -f wrongly. And from your code is still not much obvious what you want to achieve.

[itsmichaelwang]

So I'm not actually getting anything now... I want to search for the file's contents, and $line is the filename I believe. Is there a way to do that?

[itsmichaelwang]

Actually I should probably clarify. I want to find this line: return BaseView.extend({ Everything is telling me the regex should be a match, but grep returns nothing.