Question

Here is my problem.A existed file named data.f,I use collating symbol “48”,I want to match “48”in my file with Collating symbols in bracket expressions.

grep '[[.48.]]' data.f

but there is some error tip:

grep: Invalid collation character

but, there is no problem with character classes in bracket expressions.

grep "[[:alpha:]]" data.f

Answer 1

if you want to grep 48

grep 48 file

if you want to grep “48”

grep '"48"' file

// to avoid discussion in comments I extend my post with more examples

if you want to grep n occurrences of “48” in one line you should use regular expressions

cat file | grep '\(.*"48"\)\{n\}' | grep -v '\(.*"48"\)\{n+1\}'

basically you grep lines with at least n occurrences, and then with invert-match you exclude lines with n+1 occurrences of string, so you get n occurrences

in you comment you mentioned you wanted to grep lines with 5 occurrences of “48”, that CAN be separated by other characters (that’s the reason I put .* before “48”)
so here is the sample

cat file | grep '\(.*"48"\)\{5\}' | grep -v '\(.*"48"\)\{6\}'