Grepping for exact words with UNIX

问题:

I want to search Exact word pattern in Unix. Example: Log.txt file contains following text:

aaa
bbb
cccaaa   ---> this should not be counted in grep output looking for aaa

I am using following code:

count=$?
count=$(grep -c aaa $EAT_Setup_BJ3/Log.txt)

Here output should be ==> 1 not 2, using above code I am getting 2 as output. Something is missing, so can any one help me for the this please?

回答1:

Word boundary matching is an extension to the standard POSIX grep utility. It might be available or not. If you want to search for words portably, I suggest you look into perl instead, where you would use

perl -ne 'print if /\baaa\b/' $EAT_Setup_BJ3/Log.txt

回答2:

Use whole word option:

grep -c  -w aaa $EAT_Setup_BJ3/Log.txt

From the grep manual:

-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.

As noted in the comment -w is a GNU extension. With a non GNU grep you can use the word boundaries:

grep -c "\<aaa\>" $EAT_Setup_BJ3/Log.txt