regex-validate.R

library(tidyverse)

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test  = c(1231456759123, "1231456759   ", "A1231456759")
target = c(TRUE, TRUE, FALSE)

validate_char = function(x){
  l_dec = str_length(str_extract(x, "\\d+ *"))
  
  l_dec  == 13
}

validate_char(test)

## [1]  TRUE  TRUE FALSE