head() for files
On 25/07/2008 7:30 AM, Gorjanc Gregor wrote:
Hi!
I was thinking about using the head and tail functions also for files i.e.
show me the first/last few lines of a file. For example:
zz <- file("ex.data", "w") # open an output file connection
cat("TITLE extra line", "2 3 5 7", "", "11 13 17", file = zz, sep = "\n")
cat("One more line\n", file = zz)
close(zz)
readLines("ex.data")
head.character <- function(x, n=6, ...) readLines(con=x, n=n, ...)
head.character("ex.data")
As can be seen, this is essentially a wrapper for readLines, but a handy one.
Of course, S3 "linking" is needed, perhaps also for class "connection".
I am not prefectly satisfied with it as I would like to see printout line by line.
Any ideas?
I think you should have called it head.connection, and then
head(file("ex.data"))
would sort of work. The problems with this are open connections: what
should it do on one of those? Seeking to the start would make sense,
but not all connections can do that.
Duncan Murdoch