[R] How to get commands history as a character vector instead of displaying them?

[Yihui Xie]

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
>