You can also use the wildcard () to select all files in a directory.
The output highlights the string you wanted to grep.Grep patterns are regular expressions (aka regex, regexp, RE), basic regular expressions (BRE) unless one of -E/ -F/ -P/ -K/ -X option (only the first two of which being standard) is used. * is a regexp operator that matches 0 or more of the preceding atom. In BREs, when at the start of the pattern or when following the ^ or \( regexp operators, it matches a literal * only (it's also taken literally inside bracket expressions). So grep '*README.md*' matches on lines that contain a literal * followed by README followed by any single character (the. (the ^s showing what within the line is matched by the regular expression, which you could see with -color) Since any number includes 0, that's functionally equivalent to grep '*README.m' (which would make no difference to which lines are being matched, only on what may be matched within the line (which would show with the -color option of GNU grep for instance)).įor instance, it would match on those 2 lines: *README mike regexp operator) followed by m followed by any number of ds. Here, it seems you're confusing regular expressions with shell wildcard patterns. The * wildcard operator which matches on 0 or more characters can be written. Therefore, the following command would match every line in the file : grep ' ' report7 UNIX Documentation Avoids the Term Wildcard In cards, a wildcard. Would again be the same as: grep 'README\.md'Īs grep looks for a match within the line as opposed to finding lines that match the pattern exactly (for which you need -x). So with that grep implementation, you can do: grep -K 'README.md' With ast-open grep, which is also ksh93's grep builtin (not always built-in by default, and you need to enable it by putting /opt/ast/bin ahead of $PATH), you can use the -K option for grep to use shell wildcards (extended ksh93 ones). To match on lines that contain README.md. With that same implementation, wildcard matching can also be enabled within extended ( -E), augmented ( -X) or perl-like ( -P) regular expressions with the (?K) operator (and \(?K\) in basic regular expressions which actually breaks POSIX conformance, so I wouldn't rely on it as it could be removed in a future version). find one or more of any character.With any modern grep implementation, you can also do: grep -F README.mdįor a fixed-string search (where. * as previously mentioned - the dot is a wildcard character, and the star, when modifying the dot, means find one or more dot ie.
If you want * in regular expressions to act as a wildcard, you need to use. However, in regular expressions, * is a modifier, meaning that it only applies to the character or group preceding it. In the console, * is part of a glob construct, and just acts as a wildcard (for instance ls *.log will list all files that end in. * in a regular expression is not exactly the same as * in the console. If you want to just match abc, you could just say grep 'abc' myFile. * - the dot means any character ( within certain guidelines). If you want to match anything, you need to say. *abc*/ matches a string containing ab and zero or more c's (because the second * is on the c the first is meaningless because there's nothing for it to repeat). The asterisk is just a repetition operator, but you need to tell it what you repeat. Will match a string that contains abc followed by def with something optionally in between.
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