Bash script with grep -w

Question

I am using the following command: x.txt | grep -w 'in' and I am getting answers like: in into ... etc.

I only want the answer: in

How should i modify the command?

Answer 1

First, the command should be

grep -w in x.txt

Your current pipe doesn't work, and it is unnecessary to cat the file just to pipe it. grep can read files directly.

Second, the -w does exactly what you want. From the man page:

-w, --word-regexp

Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore.

grep will return the complete lines where the word occurs though; that is the function of grep; I mention it to check that you don't get confused because of that.

If you just want to return the word, as you say, you can do

grep -ow in x.txt

since -o returns only the matching part, but that seems quite unfruitful. What are you really trying to do?

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EDIT: An explicit example:

$ cat test
word in word
within word
word word
$ grep -w in test
word in word

"within" is not matched.

EDIT2: Another example:

$ grep '\<in\>' test 
word in word

EDIT3: It was given that the problem was with Swedish characters. I can reproduce this, even with the environment variable LANG set to sv_SE.UTF-8. https://stackoverflow.com/questions/9260293/egrep-accented-characters-not-recognised-as-part-of-a-word suggests using Perl for UTF-8 specific tasks as the easiest solution.

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EDIT4: It seems I can use sed to get this working with Swedish characters:

$ cat test
word den word
avträden word
word word
$ sed -n '/\bden\b/p' test
word den word
$ sed -n '/\<den\>/p' test
word den word

It is a pragmatic solution, but hopefully it works for this task.