Which is an example of pattern matching in Bash?
The following example uses pattern matching in a %% parameter expansion to remove the extension from all image files: A feature that I just recently became aware of is that you can do the above action in one fell swoop: if you use “*” or “@” as the variable name, the transformation is done on all the command-line arguments at once.
What happens when a parameter is expanded in Bash?
Bash uses the value formed by expanding the rest of parameter as the new parameter; this is then expanded and that value is used in the rest of the expansion, rather than the expansion of the original parameter.
Which is an example of substring expansion in Bash?
Here are some examples illustrating substring expansion on parameters and subscripted arrays: If parameter is ‘ @ ’, the result is length positional parameters beginning at offset . A negative offset is taken relative to one greater than the greatest positional parameter, so an offset of -1 evaluates to the last positional parameter.
Is there a glob pattern matching feature in Bash?
The bash man page refers to glob patterns simply as “Pattern Matching”. First, let’s do a quick review of bash’s glob patterns. In addition to the simple wildcard characters that are fairly well known, bash also has extended globbing, which adds additional features. These extended features are enabled via the extglob option.
How to check if a file name matches regex?
Write your pattern as one: ? and * have a different meaning in regexes; they modify what they stand after, whereas in glob patterns, they can stand on their own (see the manual ). The corresponding pattern would become: $ realFilePath=”/data/file/abcd_12bd_def_ghijk.txt” $ [ [ $mypath =~ $fileNameRegex ]] && echo “Matches!”
When to use a wildcard for pattern matching?
Wildcards allow you to specify succinctly a pattern that matches a set of filenames (for example, *.pdf to get a list of all the PDF files). Wildcards are also often referred to as glob patterns (or when using them, as “globbing”). But glob patterns have uses beyond just generating a list of useful filenames.