mjhjmtu

Suppose I have search the string which give like the following result

anything1.knownKeyWord
anything2.knownKeyWord
anything3[1].knownKeyWord

How I can write generic syntax for grep such it match all 3 string.
I have done like this

^.*w+d[?[0]?[]]?.knownKeyWord.*$ 

But I think for indexing eg [1] is not written in good way, how can I achieve so that even i replace [1] with [2342jdsjf], I don't have to change the syntax much.

Using an extended regular expression:

$ grep -E '[[:alnum:]_]+[[:digit:]]+([[^]]+])?.knownKeyWord' <file
anything1.knownKeyWord
anything2.knownKeyWord
anything3[1].knownKeyWord

This would extract any line containing a string on the format

XXXNNN[YYY].knownKeyWord

or

XXXNNN.knownKeyWord

where XXX is any non-empty alphanumeric string (that may also include _), NNN is any string of (one or more) digits, and YYY is anything not including a ].

Use grep with -x if matches are to be complete lines. Use -w if matches are supposed to be complete words (i.e. not as a substring of something else).

Just using sed to show what each part of the regular expression is matching:

$ sed -E 's/([[:alnum:]_]+)([[:digit:]]+)([[^]]+])?(.knownKeyWord)/<1><2><3><4>/' <file
<anything><1><><.knownKeyWord>
<anything><2><><.knownKeyWord>
<anything><3><[1]><.knownKeyWord>

Try this,

grep -w 'knownKeyWord$' file.txt

From man

-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.