r grep by regex - finding a string that contains a sub string exactly one once

Question

I am using R in Ubuntu, and trying to go over list of files, some of them i need and some of them i don\'t need,

I try to get the one\'s i need by finding a sub string

Answer 1

We can use stringi::stri_count:

library(stringi)
library(purrr)

# simulate some data
set.seed(1492)
(map_chr(1:10, function(i) {
  paste0(sample(letters, sample(10:30), replace=TRUE), collapse="")
}) -> strings)

## [1] "jdpcypoizdzvfzs"               "gyvcljnfmrzmdmkufq"           
## [3] "xqwrmnklbixnccwyaiadrsxn"      "bwbenawcwvdevmjfvs"           
## [5] "ytzwnpkuromfbklfsdnbwwnlrw"    "wclxpzftqgwxyetpsuslgohcdenuj"
## [7] "czkhanefss"                    "mxsrqrackxvimcxqcqsditrou"    
## [9] "ysqshvzjjmwes"                 "yzawyoqxqxiasensorlenafcbk" 

# How many "w"s in each string?
stri_count_regex(strings, "w{1}")

## [1] 0 0 2 3 4 2 0 0 1 1