Filenames Versus Patterns Metacharacters, Listed by UNIX Program Metacharacters Examples of Searching A number of UNIX text-editing utilities let you search for, and in some cases change, text patterns rather than fixed strings. These utilities include the editing programs ed, ex, vi, and sed, the awk scripting language, and the commands grep and egrep .
Double quotes suffice in most cases, but single quotes are the safest bet.