readLines!

readLines!(handle, holder, [offset=0], [length=1])

handle is the handle of the file to read.

holder is the variable that saves the data that are imported into the system.

offset (optional) is the starting position of the holder to save the lines.

length (optional) is the number of lines to read.

Read a number of lines from the handle and save them to holder starting from the given offset, and return the number of lines read.

The readLines function returns a string vector for every call. It takes a certain amount of time to create a string vector, so it saves time if we can reuse the same vector as the buffer when a function call repeats. readLines! is such a function that accepts the existing buffer as data holder. The 2 examples below read the same amount of data for 100 times. It is faster to use readLines! than readLines .

timer(100){
fin = file("test.txt")
do{ y=fin.readLines(1024) } while(y.size()==1024)
fin.close()
};
// output
Time elapsed: 79.511 ms

timer(100){
fin = file("test.txt")
y=array(STRING,1024)
do{ lines = fin.readLines!(y,0,1024) } while(lines==1024)
fin.close()
};
// output
Time elapsed: 56.034 ms