The routines to_file and
from_file are used for writing numeric arrays
to binary files with the extension .dat or .bin.
The following program demonstrates the use of to_file and from_file
for writing real data of rank 5 to a .dat file, reading the file
back into the program, and testing for exact equality to ensure that
there has been no loss in precision:
program main
use io_fortran_lib, only: to_file, from_file
implicit none (type, external)
real :: x(20,20,20,20,20)
real, allocatable :: x_dat(:,:,:,:,:)
call random_number(x)
call to_file(x, file="x.dat")
call from_file("x.dat", into=x_dat, data_shape=shape(x))
write(*,*) "x == x_dat : ", all(x == x_dat)
end program main
Warning
Reading into arrays of a different kind than the array that
was written will invalidate the data. Always make sure the kind is
matching for binary I/O.
TIP: The shape of an array may be written to a csv file so that the
value of data_shape can be read into the program before reading in
the main array with the corresponding value. The following program
demonstrates the above tip:
program main
use io_fortran_lib, only: to_file, from_file
implicit none (type, external)
real :: x(20,20,20,20,20)
real, allocatable :: x_dat(:,:,:,:,:)
integer, allocatable :: x_shape(:)
call random_number(x)
call to_file(x, file="x.dat")
call to_file(shape(x), file="x_shape.csv")
call from_file("x_shape.csv", into=x_shape)
call from_file("x.dat", into=x_dat, data_shape=x_shape)
write(*,*) "x == x_dat : ", all(x == x_dat)
end program main