Thank you very much for your suggestion...that works perfectly. Thanks, Andrew
On Mon, Apr 4, 2011 at 5:46 PM, Prof Brian Ripley <rip...@stats.ox.ac.uk> wrote: > On Mon, 4 Apr 2011, Andrew Yee wrote: > >> This has to do with using pipe() and grep and read.csv() >> >> I have a .csv file that I grep using pipe() and read.csv() as follows: >> >> read.csv(pipe('grep foo bar.csv')) >> >> However, is there a way to have this command run when for example, >> there is no "foo" text in the bar.csv file? I get an error message >> (appropriately): >> >> Error in read.table(file = file, header = header, sep = sep, quote = >> quote, : >> no lines available in input >> >> Is there a way to "inspect" the output of pipe before passing it on to >> read.csv()? > > You have to read from a pipe to 'inspect' it. So > > tmp <- readLines(pipe('grep foo bar.csv')) > if(!length(tmp)) do something else > else { > res <- read.csv(con <- textConnection(tmp)) > close(con) > } > > OTOH, unless the file is enormous you could simply read it into R and use > grep(value = TRUE) on the character vector. > >> >> Thanks, >> Andrew >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> > > -- > Brian D. Ripley, rip...@stats.ox.ac.uk > Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ > University of Oxford, Tel: +44 1865 272861 (self) > 1 South Parks Road, +44 1865 272866 (PA) > Oxford OX1 3TG, UK Fax: +44 1865 272595 > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.