when reading data from standard input ( stdin ), they are duplicated in standard output ( stdout ). examples:

$ echo "10" | r -e 'x<-readLines()' 10 $ echo "10" | r -e 'x<-scan(quiet=T)' 1: 10 2:

How to avoid this duplication?

  • one
    @AK, no, I do not want. - aleksandr barakin

1 answer 1

Although it is written in the description of both functions that the default reading is from stdin , you should explicitly open stdin using the file() function and pass the object it created to the mentioned reading functions (argument con for readLines() and file for scan() ).

 $ echo "10" | r -e 'x<-readLines(con=file("stdin"))' $ echo "10" | r -e 'x<-scan(file=file("stdin"),quiet=T)' $

Examples supplemented with real processing of the entered data and output of results:

 $ echo "10" | r -e 'x<-readLines(con=file("stdin")); cat(as.numeric(x[1])+1)' 11 $ echo "10" | r -e 'x<-scan(file=file("stdin"),quiet=T); cat(x[1]+1)' 11

ps in the case of the scan() function, you can even do without calling the file() function, immediately passing the value stdin file argument:

 $ echo "10" | r -e 'x<-scan(file="stdin",quiet=T); cat(x[1]+1)' 11