Why does grep return no results (list all files in directory)

I'm trying to count all files in a directory that match a pattern, recursively, using ls:

ls -R | grep *.{cpp,h} | wc

However, I get:

zsh: no matches found: *.cpp

ls -R does return results, though:

$ ls -R CMakeLists.txt cmake src

./cmake: Modules SUBS.cmake

./cmake/Modules: FindGecode.cmake

./src: A1_examples.h Sub1Main.cpp Sudoku.cpp Sudoku.h nQueens.cpp

Why doesn't grep find the *.cpp files that ls -R returns?

Edit: I'm also pretty sure that ls -R | grep *.{cpp,h} | wc is not the best way to do this, because of the way that ls returns multiple results on single lines, but I'm not certain.

simont

Posted 2012-04-09T11:59:16.453

Reputation: 1 113

what kind of syntax is {cpp,h} ? – barlop – 2012-04-09T12:01:05.507

1As to the multiline: compare ls to ls | cat sometime. ls is smart enough to do multicolumn only when reporting directly (or when told to do so explicitly); it assumes -C for terminals and -1 for pipes. – geekosaur – 2012-04-09T12:07:53.307

Answers

You're making two different mistakes that play together. First, you need to quote the pattern sent to grep, otherwise the shell will expand it first. (That's where the error message comes from.) Second, grep does not accept shell globs, it wants a regex.

zsh being what it is, you may want to say

$ ls **/*.{cpp,h} | wc -l

instead, using a zsh-style recursive glob. If you want to use the other one, it's

$ ls -R | egrep '\.(cpp|h)$' | wc -l

geekosaur

Posted 2012-04-09T11:59:16.453

Reputation: 10 195

Thanks. I've just been trying to get it working with plain grep rather than egrep (because I didn't know what the differences were). For my future reference: egrep is grep -E (enabled use of extended regular expressions; the brackets in the answer only work if the regular expression is an extended one). – simont – 2012-04-09T12:31:29.863

1egrep is the original; grep -E is a GNUism. Also a GNUism is that you can use escaping instead: grep '\.$cpp\|h$'. Neither is portable. – geekosaur – 2012-04-09T12:32:59.627