I have read
How to set max ppsize in R?
and I have the same problem. I am currently working in Rstudio and I need to set max ppsize to a greater value.
It looks like, you were writing this code into the R-console. But with "command line" its is meant what you upen under windows by searching for cmd (s. e.g. this video for windows or this for mac OS X or this for Linux).