IO commands

To read or write on a file in Fortran one must first open it. To open a file name mytextfile.txt one can write
open(unit=10, file="mytextfile.txt", status = new/old, action = read/write)
Only the first two argument (unit and file) are mandatory. You can choose any integer for unit (it can also be a variable integer), as long as it is not used by another file (for example mytextfile_2.txt).
After working on the file, you need to close it with the command
close(10)

Reading

Fortran will read line by line, so if your file is a data file with one observation per line and 5 variables, say, you can get this data into a matrix in the following way
do j=1,15
read(10,*) var1(j) var2(j) var3(j) var4(j) var5(j)
end do

Writing

To write in a file, if you have a matrix with N lines with an identifier and a result (scalar) you can write
do j=1,N
write(10,*) (matresult(j,i),i=1,2)
end do
Last modified 4yr ago