Set difference

setdiff.R

#!/usr/bin/env Rscript

args <- commandArgs(trailingOnly = TRUE)

if (length(args) < 2) {
	cat("Usage: setdiff <file1> <file2> [files]\n", file = stderr())
}

ignorecase <- FALSE
if (args[[1]] == "-i") {
	ignorecase <- TRUE
	args <- args[-1]
}

if (ignorecase) {
	set <- tolower(readLines(args[[1]]))
} else {
	set <- readLines(args[[1]])
}

for (afile in args[-1]) {
	if (ignorecase) {
		set <- setdiff(set,tolower(readLines(afile)))
	} else {
		set <- setdiff(set,readLines(afile))
	}
}

writeLines(set)