fork(1) download 
  1. x <- c("not line_start 1 abc 2 def 4", "line_start 1 abc 2 def 4")
  2. regmatches(x, gregexpr("(?:\\G(?!^)|^line_start)\\D*\\K\\d+", x, perl=TRUE))
Success #stdin #stdout 0.22s 39532KB
comments (?)
stdin 
Standard input is empty
stdout 
[[1]]
character(0)

[[2]]
[1] "1" "2" "4"
https://ideone.com/tlSNzs
language:
R (R 3.5.2)
created:
6 years ago
visibility:
secret

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!