demo_parse.R

a <- "X123456789050102550703
A123456987050102660703
B123456789050102"
gregexpr("(?<id>[A-Z]\\d{9})(?<b_date>\\d{6})(?<d_date>\\d{6}){0,1}", a, perl=TRUE)
# [[1]]
# [1]  1 24 47
# attr(,"match.length")
# [1] 22 22 16
# attr(,"useBytes")
# [1] TRUE
# attr(,"capture.start")
#      id b_date d_date
# [1,]  1     11     17
# [2,] 24     34     40
# [3,] 47     57      0
# attr(,"capture.length")
#      id b_date d_date
# [1,] 10      6      6
# [2,] 10      6      6
# [3,] 10      6      0
# attr(,"capture.names")
# [1] "id"     "b_date" "d_date"