Subset according to patterns in file names

Question

I have the following file names in a folder:

1_myfile.txt, 2_myfile.txt, 3_myfile.txt, and 4_best_myfile.txt, 5_best_myfile.txt, 6_best_myfile.txt.

I would like to use regex in pattern = "" when listing files with list.files() in order to subset files containing "_myfile.txt" from files containing "_best_myfile.txt". I tried using:

 files = list.files(path = ".", "*[^best_myfile.txt]$") 

Unfortunately it does not work because it subsets only files that do not end with .txt. How can I solve this?

Answer 1

We can modify the pattern to "\\d+_best_myfile\\.txt"

files <- list.files("\\d+_best_myfile\\.txt") 

It implies one or more numbers (\\d+) followed by a _ and the string best_myfile.txt. Also, note that some characters needs to be escaped i.e. . is a metacharacter and it implies any character. So, to get the literal dot character, we need to escape (\\) it