is there a way to read a specific column from a txt file

Sometimes, it is too costly to read the whole data file into R.
I am looking for solution in scan() and read.Lines() but don't they work.

Try the following (assuming a 3 columns data file):

mydata <- read.table(file="myfile",header=T,colClasses=c(NA,"NULL",NA))

"NULL" indicates the column to be omitted.

Hope this helps you,

Paul