How to get commands history as a character vector instead of displaying them?
Thanks, Wacek and Romain! Your solutions worked very well in RGui and Rterm in interactive mode. My final purpose was to obtain the file name of the postscript device in Rweb (http://pbil.univ-lyon1.fr/Rweb/); now I found savehistory() would not work because Rweb was non-interactive. I didn't realize it until I try(savehistory()) and got an error message. Now I found a solution by myself: we can list the *.ps files and pick the most recently created (modified, visited, ...) one, e.g. x = file.info(list.files(pattern = ".*\\.ps$")) x = x[order(x$atime), ] rownames(x)[nrow(x)] Regards, Yihui -- Yihui Xie <xieyihui at gmail.com> Phone: +86-(0)10-82509086 Fax: +86-(0)10-82509086 Mobile: +86-15810805877 Homepage: http://www.yihui.name School of Statistics, Room 1037, Mingde Main Building, Renmin University of China, Beijing, 100872, China On Mon, Mar 23, 2009 at 6:13 PM, Wacek Kusnierczyk
<Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> wrote:
Romain Francois wrote:
Yihui Xie wrote:
Hi Everyone, I want to get the commands history as a character vector instead of just displaying them, but the function history() just returns NULL. I checked the source code of 'history' and could not find a solution. Anybody has an idea? Thanks!
history eventually calls file.show, which will use the pager option to
determine how to show the file, so you can do something like that:
history <- function( ... ){
old.op <- options( pager = function( files, header, title, delete.file
) readLines( files ) ); on.exit( options( old.op ) )
utils::history(...)
}
history( pattern = "png" )
i think the following is an acceptable alternative:
? ?history = function() {
? ? ? file = tempfile()
? ? ? on.exit(unlink(file))
? ? ? savehistory(file)
? ? ? readLines(file) }
the output is *lines* of text, but if you need whole executable
expressions, you can parse the output:
? ?1 + 1
? ?ph = parse(text=history())
? ?as.list(ph)
? ?ph[length(ph)-1]
? ?# expression(1 + 1)
? ?eval(ph[length(ph)-1])
? ?# [1] 2
vQ