Sometimes you don't want to actually capture the string, you just want to match it. Using the parenthesis groups foo|bar into a capture-group, so the surrounding \b will be applied to anything inside the parenthesis, reducing the noise. There's a lot of duplication in that little pattern though, and regular expressions let us trim out the replication: %w.grep(/\b(foo|bar)\b/) # => For our purposes though \b and the default behavior is probably fine. I STRONGLY recommend reading about that as there are additional potential issues you can run into. \w is the pattern used, and it's defined in the Regexp documentation. The \b means a "word-boundary" which is the transition between a non-word character and a word character. To fix this we have to tell the regex engine to only find words: %w.grep(/\bfoo\b|\bbar\b/) # => foo|bar/ are actually matching substrings, not complete words: %w.grep(/foo|bar/) # => Grep Multiple Patterns GNU grep supports three regular expression syntaxes, Basic, Extended, and Perl-compatible.
#Grep multiple strings from same file how to#
This isn't the entire solution because there are dragons waiting in the woods. Bash scripting tutorial for beginners In this article, we’re going to show you how to use GNU grep to search for multiple strings or patterns. grep will iterate over the array, and finds both. | means "or", so the pattern /foo|bar/ is looking for "foo" or "bar". this will look for all files containing filename in the file's name under the /path/to/dir, than for every file found, search for the line with searchstring and replace old with new. It isn't entirely clear what you're asking, but from the context it looks like you want a pattern that can be used to search for multiple entries in an array, since readlines returns an array containing the lines of the file.Ī simple pattern example would be: %w.grep(/foo|bar/) # =>
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