# Sending nohup commands to R scripts

How I use nohup commands for time consuming R projects

There are times when I am connected remotely to an RStudio server and I want to run a time-consuming script which might take a few hours or days. As part of my PhD I had to calculate a number of large distance matrices which took considerable time since the data was quite large. Another script I developed was to download and parse 150,000 documents. It took a week to download and parse them and during this time I lost connection to the server a few times causing the code to break.

The free version of RStudio only allows one session open at any time and leaving the script running for a week meant that I couldn’t keep coding in R! Many of the problems I faced actually didn’t require RStudio since the models were either downloading and storing data or calculating matrices so just an R connection would be sufficient. So, I wanted to find a way to run an R file without logging off or without any interruption. I come across the nohup command in Unix operating systems.

The nohup or no hang-up command can execute a script and tell the system to continue running it even if the session is disconnected. I use it in the following way, once I have developed a model myRFile.R using RStudio, verified it works on a sample of the data etc. and saved it into a folder called myFolder. I can go to the terminal (which I usually connect to using PuTTY) and run the following:

nohup Rscript ./myFolder/myRFile.R </dev/null>myRFile_Output.out 2>myRFile_ErrorMessages.err &

This will run the .R file and store any output usually printed to the console to a text file myRFile_Ouput.out and any error messages to another text file myRFile_ErrorMessages.err where we can check on the progress whilst the script is running. I usually add progress messages in side the function such as:

foo <- function(x){
print(paste("Year", x, "has started ", Sys.time()))

do.something

print(paste("Year", x, "has ended ", Sys.time()))
return(x)
}

years <- seq(from = "2005", to = "2018")
sapply(years, foo)  

Which prints out the progress of the function to myRFile_Output.out, i.e. if I needed to apply a function across years.

By running nohup commands from the terminal allows me to free up my RStudio for other tasks also.

##### Matthew Smith
###### Researcher in Dept Finance

I am a researcher with a focus on Machine Learning methods applied to economics and finance.