Read a text file in R line by line

Question

I would like to read a text file in R, line by line, using a for loop and with the length of the file. The problem is that it only prints character(0). This is the code:

fileName="up_down.txt" con=file(fileName,open="r") line=readLines(con)  long=length(line) for (i in 1:long){     linn=readLines(con,1)     print(linn) } close(con) 

Answer 1

You should take care with readLines(...) and big files. Reading all lines at memory can be risky. Below is a example of how to read file and process just one line at time:

processFile = function(filepath) {   con = file(filepath, "r")   while ( TRUE ) {     line = readLines(con, n = 1)     if ( length(line) == 0 ) {       break     }     print(line)   }    close(con) } 

Understand the risk of reading a line at memory too. Big files without line breaks can fill your memory too.