Use multicore package (R on MacOS) to grep a (Very Large Data) file-as-dataframe.

R_multicore_example

### manage memory on a large data set using multicore library
library(multicore)

# read in tab-delimited file from working dir
df = read.table(getwd(), sep="\t", header=T)
d.lines = as.character(df$charvar)            # $charvar is character-class variable you want to grep

grep_wrap <- function (pattern, x, ignore.case = FALSE, perl = FALSE, value = FALSE, fixed = FALSE, useBytes = FALSE, invert = FALSE) {
    ret = rep(0, length(x))
    ret[grep(pattern, x, ignore.case, perl, value, fixed, useBytes, invert)] = 1
    ret
}

result = pvec(d.lines, grep_wrap, pattern="\\d{7,10}\\>") # example pattern finds 7-10 digits at the end of input string