R, check if special character in string

Question

How to use R to check if a string contains at least one of the following characters, /\:*?"<>|. Also, I hope the string can contain any other characters, e.g. -.

Actually these characters are the ones not allowed for windows directory (folder) name.

something like `myStr <- "this/string"; grepl("[[:punct:]]", myStr)` ? — SymbolixAU, Jul 13 '17 at 01:46
@SymbolixAU, no because `grepl("[[:punct:]]", "-")` is true. — WCMC, Jul 13 '17 at 01:46
just make your pattern a bit more explicit: `myStr <- "thisstring"; grepl("/|:|\\?|<|>|\\|\\\\|\\*", myStr)` — SymbolixAU, Jul 13 '17 at 01:49
@SymbolixAU Why not post that as an answer? Akrun is asleep right now, go on! — Tim Biegeleisen, Jul 13 '17 at 01:55

SymbolixAU · Accepted Answer · 2021-08-09T09:52:36.013

Define the pattern(s) you want to find in the string, then use grepl to find them

pattern <- "/|:|\\?|<|>|\\|\\\\|\\*"

myStrings <- c("this/isastring", "this*isanotherstring", "athirdstring")

grepl(pattern, myStrings)
# [1] TRUE TRUE FALSE

A break down of pattern:

if it were

pattern <- "/"

This would just search for "/"

The vertical bar/pipe is used as an 'OR' condition on the pattern, so

pattern <- "/|:"

is searching for either "/" OR ":"

To search for the "|" character itself, you need to escape it using "\"

pattern <- "/|:|\\|"

And to search for the "" character, you need to escape that too (and similarly for other special characters, ?, *, ...

pattern <- "/|:|\\?|<|>|\\|\\\\"

Reference: Dealing with special characters in R

R, check if special character in string

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