Ubuntu 14.04中的Grep

Question

I just recently updated my Ubuntu VM to 14.04 and before this I could run the grep command

grep -nr "piece of text"

or any other grep command for that matter and it would finish in 2-10 seconds in the directory I was working on. Now for some reason (no idea if this was caused by the update) running any grep command in the same dir I was working in just seems to hang there (idk if it does complete because I don't want to wait over a min or so for a search to happen) instead of showing my results. Any idea of what's happening or what I can do and try to fix it?

Answer 1

You aren't specifying the files to grep, so it's trying to read STDIN. I think you wanted

grep -nr "piece of text" *

Note the asterisk is globbed to all files in the current path.

Answer 2

which grep are you using ? -r option default to '.' directory in gnu case

which grep :
/bin/grep --version
/bin/grep (GNU grep) 2.18)
...
this is gnu grep :

echo "truc" >/tmp/truc

cd /tmp; grep -nr "truc";

using gnu grep -> it search recursively files in . of current directory ( here in /tmp ) and displays them containing "truc"

if /bin/grep --version is busybox :

BusyBox v1.22.1 (Debian 1:1.22.0-8) multi-call binary.

Usage:

grep [-HhnlLoqvsriwFEz] [-m N] [-A/B/C N] PATTERN/-e PATTERN.../-f FILE [FILE]...

using busybox : cd /tmp; busybox grep -nr "truc"; cd /tmp; busybox grep -nr "truc";

wait indefinitely that you type content of file on STDIN ( stop with Ctrl + C ).

it reads STDIN as a file ( not even caring that -n indicates a directory recursion ).

Answer 3

As others answered, and as POSIX grep or GNU grep documentation tells, you need to specify some file to the standard grep command. (But GNU grep defaults to current directory . if -r is given without a directory name; however if -r is not given at all, grep defaults to read - ie the stdin ).

BTW, I would also recommend the ack utility, packaged as the ack-grep package on Ubuntu or Debian. It does not need any files (default is the source code files under current directory) and it avoids useless non-source files (version control or object files...):

 ack "piece of text"

Also, under emacs , you can use Mx grep