RegexOne - Learn Regular Expressions - Problem 5: Matching specific filenames

Problem 5: Matching specific filenames

If you use Linux or the command line frequently, are often dealing with lists of files. Most files have a filename component as well as an extension, but in Linux, it is also common to have hidden files that have no filename.

In this simple example, extract the filenames and extension types of only image files (not including temporary files for images currently being edited). Image files are defined as .jpg,.png, and .gif.

Exercise 5: Capturing filename data

Task	Text	Capture Groups
skip	.bash_profile
skip	workspace.doc
capture	img0912.jpg	img0912 jpg
capture	updated_img0912.png	updated_img0912 png
skip	documentation.html
capture	favicon.gif	favicon gif
skip	img0912.jpg.tmp
skip	access.lock

Solution

We are only looking for image files ending with the 'jpg', 'png' and 'gif' file extensions, so we can capture all such filenames using the expression (\w+)\.(jpg|png|gif)$.

Solve the above task to continue on to the next problem, or read the Solution.

Lesson Notes

	abc…	Letters
	123…	Digits
	\d	Any Digit
	\D	Any Non-digit character
	.	Any Character
	\.	Period
	[abc]	Only a, b, or c
	[^abc]	Not a, b, nor c
	[a-z]	Characters a to z
	[0-9]	Numbers 0 to 9
	\w	Any Alphanumeric character
	\W	Any Non-alphanumeric character
	{m}	m Repetitions
	{m,n}	m to n Repetitions
	*	Zero or more repetitions
	+	One or more repetitions
	?	Optional character
	\s	Any Whitespace
	\S	Any Non-whitespace character
	^…$	Starts and ends
	(…)	Capture Group
	(a(bc))	Capture Sub-group
	(.*)	Capture all
	(abc\|def)	Matches abc or def