list.files pattern argument in R, extended regular expression use

Question

I run

  dir.create(\'./junk_data\')
  file.create(paste(\'./junk_data/QWE\',01:12,01:31,2005:2015,\'.3\',sep=\'\'))
  file.create(paste(\'./junk_data/RTY\',0         


        

Answer 1

As Arun showed in his example, a dot usually means "match any character", so to match a dot you need to escape it: \\.. You can create the pattern most easily with glob2rx, which uses * as a wildcard and matches other characters as though they are fixed.

glob2rx("QWE*2011.3")   #"^QWE.*2011\\.3$"
list.files("./junk_data/", pattern = glob2rx("QWE*2011.3"), full.names = TRUE)