glob2rx: Change Wildcard or Globbing Pattern into Regular Expression

Description

Change wildcard aka globbing patterns into the corresponding regular expressions (regexp).

Usage

glob2rx(pattern, trim.head = FALSE, trim.tail = TRUE)

Arguments

pattern

character vector

trim.head

logical specifying if leading "^.*" should be trimmed from the result.

trim.tail

logical specifying if trailing ".*$" should be trimmed from the result.

Value

A character vector of the same length as the input pattern where each wildcard is translated to the corresponding regular expression.

Details

This takes a wildcard as used by most shells and returns an equivalent regular expression. ? is mapped to . (match a single character), * to .* (match any string, including an empty one), and the pattern is anchored (it must start at the beginning and end at the end). Optionally, the resulting regexp is simplified.

Note that now even (, [ and { can be used in pattern, but glob2rx() may not work correctly with arbitrary characters in pattern.

Examples

Run this code

stopifnot(glob2rx("abc.*") == "^abc\\.",<!-- % '\\' doubled in Rd file! -->
          glob2rx("a?b.*") == "^a.b\\.",
          glob2rx("a?b.*", trim.tail = FALSE) == "^a.b\\..*$",
          glob2rx("*.doc") == "^.*\\.doc$",
          glob2rx("*.doc", trim.head = TRUE) == "\\.doc$",
          glob2rx("*.t*")  == "^.*\\.t",
          glob2rx("*.t??") == "^.*\\.t..$",
          glob2rx("*[*")  == "^.*\\["
)