Grep, ignore warnings

Question

I am trying to find the installation directory of a particular package. I have a certain keyword using which I am trying to find a particular file.

During grep, I only want to include cpp or h file type. I do not want the grep to show warnings like Permission Denied or Could not find the Directory. I just want it to display matched files, nothing else. Please suggest how can I do this?

At present I am using

grep "My term" -ir --exclude-dir="\.svn" --include=*.{cpp,h} ./

score 72 · Accepted Answer · edited Feb 05 '17 at 18:00

72

Those warnings are directed to the stderr stream, as opposed to the standard out file descriptor. You can silence the stderr output by adding 2>/dev/null to the end of your command.

edited Feb 05 '17 at 18:00

Sergiy Kolodyazhnyy

103,293
19
273
492

answered Mar 26 '11 at 14:26

James Henstridge

40,476
13
109
92

2

Te be more specific ```find . 2>/dev/null | grep 404.html``` is what a command would look like – csga5000 Mar 21 '18 at 21:12
Not the end of the command, but at the start of the command. (arch linux) example : `2>/dev/null ifconfig | grep inet` This will show you your local ip without any error. – Khan Saad Sep 27 '22 at 08:12

score 34 · Answer 2 · answered May 25 '13 at 14:15

More directly than filtering the warnings you can disable them by adding -s:

grep "My term" -sir --exclude-dir="\.svn" --include=*.{cpp,h} ./

There are some compatibility issues with this option. However, this shouldn't be a problem for personal use.

-s, --no-messages: Suppress error messages about nonexistent or unreadable files. Portability note: unlike GNU grep, 7th Edition Unix grep did not conform to POSIX, because it lacked -q and its -s option behaved like GNU grep's -q option. USG-style grep also lacked -q but its -s option behaved like GNU grep. Portable shell scripts should avoid both -q and -s and should redirect standard and error output to /dev/null instead. (-s is specified by POSIX.)

I just installed 13.04 and I am getting the errors which I was not getting with 12.04. Could it be that something changed? I thought it was cool that grep would stop warning about files being directories since in most cases I just don't care! — Alexis Wilke, Oct 12 '13 at 20:34

andrewtweber · Answer 3 · 2015-11-23T21:42:36.200

I used to get a ton of annoying messages like this:

grep: commands: Is a directory
grep: events: Is a directory
grep: views: Is a directory

The reason is that the --directories flag is defaulted to read. I changed it to recurse; if you don't want it to automatically do a recursive search you can use skip instead.

The easiest way to handle this all the time is to set it in an environment variable. In ~/.bash_profile or ~/.bashrc depending on your distro:

export GREP_OPTIONS='--directories=recurse'

Now it automatically suppresses those messages any time I use grep.

Another option is the --no-messages flag, shorthand -s. This will also get rid of the Is a directory messages, but it also suppresses other messages which might be more useful. For example, if you're doing a nested search in */*/* and no such file of that pattern exists, it won't tell you that.

The downside of the `--directories=recurse` option, of course, is that it always performs a recursive grep, even when you know that you just want to grep files in the current folder. Problematic in an era of `node_modules`, for example. — jarmod, Mar 03 '21 at 15:49

score 1 · Answer 4 · answered Feb 05 '17 at 18:10

Alternative approach instead of doing grep recursively with -ir would be to let find command (which is recursive by default) handle the permissions with -readable flag and path's to exclude with -not -path "*.svn*" flags, and then pass the file to grep. Excluding directories is done via -type f for finding only regular files.

$ find . -not -path "*.svn*" -type f -name "*.cpp" -or -name "*.h"  -readable -exec grep "my terms" "{}" \;

score 0 · Answer 5 · edited Sep 11 '16 at 02:54

When doing recursive searches in specific files, you are much better off using ack-grep. The syntax here would be:

ack-grep -i "My term" --cpp --h

To remove the permission error messages, you may want to run the same command with sudo:

ack-grep -i "My term" --cpp --h

But eventually, if you want to search installed packages, look at those various options: https://www.google.com/search?q=ubuntu%20search%20inside%20installed%20packages

Grep, ignore warnings

5 Answers5