Error: grep: find: Is a directory

Question

I am new to Linux and going through some tutorials and samples. I created a file called test and put alex and alexander in it. I'm trying to find instances of just alex .

If I do grep alex * I get the error:

grep: find: Is a directory.

If I do cat test | grep alex cat test | grep alex then I get (as expected)

alex
alexander (with alex in red)

Why does the first cause an error, and the second produce expected results?

Answer 1

If you want to grep phrase from specific file use:

# grep "alex" test

In case you use grep alex * it will search through all files inside the current work directory. In case subdirectory will be met it will tell you something like grep: find: Is a directory
If you want to perform a recursive search use -r key. For example

# grep -r "alex" /some/folder/

In this case all files and files inside subdirectories from /some/folder/ will be checked.
And you can always use man grep .

Answer 2

正确答案是：

grep -d skip alex /etc/*

Answer 3

Setting the environmental variable GREP_OPTIONS to include the value "--directories=skip" should suppress that “Is a directory” message (ie enter GREP_OPTIONS="--directories=skip" or add that line to one of your login initialization files like .bashrc to make that behavior permanent).

> cat test
alex
alexander

> grep alex *    
grep: mysql_data: Is a directory
grep: sql_updates: Is a directory
test:alex
test:alexander
grep: tmp_files: Is a directory

> GREP_OPTIONS="--directories=skip"

> grep alex *                      
test:alex
test:alexander

Also since there is a command named “test” and another named “find” it's usually not advisable to use those as file or directory names. That shouldn't be a problem here but it can lead to other conflicts.

Answer 4

If you wanted to go through all the directories including the find directory, you can run this command:

grep alex * -r

Which will go through all the directories in your current directory recursively.

Answer 5

Or using grep with -l flag or -w flag

$ grep -l alex /etc/* 

To return list of files containing word "alex" in the /etc directory

$ grep -w alex /etc/*

To return list of lines from files in the /etc directory containing "alex" word