If we have a short R script or a single R function we can emberd this R command into a bash script and process it using one cores using the bash EOF function.
The export bash fonticon and the Sys.getenv() R function allows to exchange variables between R and bash. We can use this functionality to embed an R command in bash.

cd ~/Documents/multi_core
mod=1
t=24
path=~/Documents/multi_core/output
export mod
export t
export path
 
R --vanilla --no-readline   -q  << EOF
mod.t = Sys.getenv(c('mod','t','path'))
mod = as.numeric(mod.t[1])
t = as.numeric(mod.t[2])
path = as.character(mod.t[3])
print(mod)
print(t)
print(path)
my_output=paste("We have processed  mod ",mod," and t ",t," ---- output path is   ",path,sep=" ")
write.table(my_output,paste(path,"/mytext.txt",sep=""))
EOF

We can built an R script using Sys.getenv() and launch it in a loop using multi cpu