I have a bunch of parameters which are being written out but I want to add an extra 256 bytes to that line.
open (1, file=filename, form='unformatted')
write (1) a,b,c,d,BLANKBYTES
write (1) array1
write (1) array2
close (1)
Is there a way to add these extra 'blank' bytes?
use ISO_FORTRAN_ENV
integer (int8), dimension (256), parameter :: zero_bytes = 0
....
write (1) a,b,c,d, zero_bytes
Another approach.
write(1)a,b,c,d,(char(0),i=1,256)
Related
I am trying to read a text file using a Fortran code. I have a file with 1999 rows and the number of columns vary with each row. Can someone please tell me how one can code such a problem. This is my code for reading a 4*2 text file but I am using do loops which I can't use in my current case.
PROGRAM myread2
IMPLICIT NONE
INTEGER, DIMENSION(100) :: a, b
INTEGER :: row,col,max_rows,max_cols
OPEN(UNIT=11, file='text.txt')
DO row = 1,4
READ(11,*) a(row), b(row)
END DO
PRINT *, a(1)
PRINT *, a(4)
PRINT*, b(4)
END PROGRAM myread2
The best way of reading a file like this depends on how you want to store the data. I'm going to use a ragged array as it's probably simplest, although other container types may be better suited depending on your requirements.
Fortran doesn't have ragged arrays natively, so first you need to define a type to hold each row. This can be done as
type :: RowData
integer, allocatable :: cols(:)
end type
type(RowData), allocatable :: rows(:)
When this container is filled out, the value in the i'th column of the j'th row will be accessed as
value = rows(j)%cols(i)
We can then write a program to read the file, e.g.
type :: RowData
integer, allocatable :: cols(:)
end type
type(RowData), allocatable :: rows(:)
integer :: no_rows
integer :: i
open(unit=11, file='text.txt')
no_rows = count_lines(11)
allocate(rows(no_rows))
do i=1,no_rows
rows(i)%cols = read_row(11)
enddo
Now we just need to write the functions count_lines, which counts the number of lines in the file, and read_row, which reads a line from the file and returns the contents of that line as an array of integers.
Following this question, count_lines can be written as
! Takes a file unit, and returns the number of lines in the file.
! N.B. the file must be at the start of the file.
function count_lines(file_unit) result(output)
integer, intent(in) :: file_unit
integer :: output
integer :: iostat
output = 0
iostat = 0
do while (iostat==0)
read(file_unit, *, iostat=iostat)
if (iostat==0) then
output = output+1
endif
enddo
rewind(file_unit)
end function
Writing read_row, to parse a line of unknown length from a file, can be done by following this question.
I was trying to copy contents of a file to a string array and I couldn't manage to fully copy the file (it was only copying the first characters in every line). I feel like something is wrong with my syntax and its possible to do it with character, dimension(:,:) but it worked with character(:), dimension(:).
This doesn't work as expected:
character, allocatable :: list(:,:)
integer :: i, line_count, line_length
open(1, "input.txt", status="old", action="read")
line_count = count_file_lines(1) ! function that returns integer
line_length = longest_line_length(1) ! function that returns integer
allocate(list(line_count, line_length))
do i = 1, line_count
read(1, *) list(i,:)
end do
close(1)
This works as expected:
character(:), allocatable :: list(:)
integer :: i, line_count, line_length
open(1, "input.txt", status="old", action="read")
line_count = count_file_lines(1) ! function that returns integer
line_length = longest_line_length(1) ! function that returns integer
allocate(character(line_length) :: list(line_count))
do i = 1, line_count
read(1, *) list(i)
end do
close(1)
I've tried switching indexes in the first example and it still didn't work. I understand that the first example is a rank 2 character array but what is the array in the second example? Maybe they both are the same type of array and I got the indexing wrong for the first one. Can someone clarify this?
In the first example you have a 2D array of single characters, of character strings of size 1. In the other example you have a 1D array of longer character strings. See Difference between "character*10 :: a" and "character :: a(10)" for the difference.
The readstatement regards each of the character in the 2D array as a separate variable it tries to read. That is why it appears storing only the first character each time. The list-directed format * you are using is not good enough for reading a character array.
You can actually read a line to a character array, but you have to read it as an array and use the appropriate format
read(1, '(*(a))') str(i,:)
You are responsible to make sure that three are enough characters on each line of your file for your arrays.
You must also be careful when printing the content, which you do not show.
Be aware that using unit 1 for your files is poor form. Unit numbers below 10 are often pre-connected by the compiler to standard input, standard output, standard error and possibly other files.
I am having trouble reading exponential from a text file using Fortran.
The entry in the text file looks like the following
0.02547163e+06-0.04601176e+01 0.02500000e+02 0.00000000e+00 0.00000000e+00 3
And the code that I am using looks like the following
read(iunit,'(ES20.8,ES20.8,ES20.8,ES20.8,ES20.8,I2)') dummy1, dummy2, Thermo_DB_Coeffs_LowT(iS,1:3),temp
The error I am getting is
Fortran runtime error: Bad value during floating point read
How can I read these values?
Well here is what I usually do when it is too painful to hand edit the file...
CHARACTER(LEN=256) :: Line
INTEGER, PARAMETER :: Start = 1
INTEGER :: Fin, Trailing_Int, I
DOUBLE, DIMENSION(6) :: Element
...
Ingest_All_Rows: DO WHILE(.TRUE.)
READ(...) Line ! Into a character-string
<if we get to the end of the file, then 'EXIT Ingest_All_Rows'>
Start =1
Single_Row_Ingest: DO I = 1, 6
Fin = SCAN(Line,'eE')+3 !or maybe it is 4?
IF(I ==6) Fin = LEN_TRIM(Line)
READ(Line(Start:Fin),*) Element(I) !fron the string(len-string) to the double.
Line = Line((Fin+1):)
IF(I ==6) Trailing_Int = Element(6)
ENDDO Single_Row_Ingest
<Here we shove the row's 5 elements into some array, and the trailing int somewhere>
ENDDO Ingest_All_Rows
You will have to fill in the blanks, but I find that SCAN and LEN_TRIM can be useful in these cases
I need to read from a txt file into three arrays in order to calculate distances between coordinates. I have looked through other answers and pieced together the script bellow. The columns of the input file need to be come my x, y and z arrays respectively. There are 64 rows and 16 decimal places for each entry. Pointers would be greatly appreciated.
the data format:
0.8607595188703266 0.9252035918116585 0.4094258340665792
0.5246038490998378 0.9804633529144733 0.5325820695466118
0.6955271184611949 0.3304908806613460 0.7154502550542654
and my script so far:
PROGRAM readtest
use, intrinsic :: iso_fortran_env
implicit none
integer, parameter :: ArrayLen = 64
real(real64), DIMENSION(ArrayLen) :: x
real(real64), DIMENSION(ArrayLen) :: y
real(real64), DIMENSION(ArrayLen) :: z
integer :: i, ReadCode, num
OPEN(1, FILE='contcar.txt', STATUS='old', ACTION='read')
OPEN(2, FILE='xyz.txt', STATUS='replace', ACTION='write')
num = 0
ReadLoop: do i=1, ArrayLen
read (1, '(A,F18.16)', iostat=ReadCode ) x(i), y(i), z(i)
if ( ReadCode /= 0 ) then
if ( ReadCode == iostat_end ) then
exit ReadLoop
else
write ( *, '( / "Error on read: ", I0 )' ) ReadCode
stop
end if
end if
num = num + 1
end do ReadLoop
WRITE(3, 100) x, y, z
100 format (A,F18.16)
END PROGRAM readtest
The xyz.txt is appearing blank and I am not getting any errors at this stage, what is wrong here that is stopping the array filling and writing to the file?
Sorry, if this is too much of mess to approach, any help would be appreciated.
Thanks
You have two problems with you approach:
Your format specifications are wrong
Your write won't do what you want
First off, the format A,F18.16 reads two items, a character and a floating point number. What you want is to read 3 floating point numbers. With the file provided, there are two spaces before each number so you could use
read (1, '(3(2X,F18.16))', iostat=ReadCode ) x(i), y(i), z(i)
but this is not very flexible if your input format changes and it is easier to just do list-directed input:
read (1, *, iostat=ReadCode ) x(i), y(i), z(i)
which will do what you want and is not sensitive to the exact positioning of the numbers within the file and how many intervening spaces exist.
This will load your data into the arrays. Now for output you want the same thing. You want to duplicate the output so we can use the first format about to stipulate that output (3(2X,F18.16)). This will output 3 numbers per line with 2 spaces before each number. The next problem is that you are attempting
WRITE(3, 100) x, y, z
which will transpose your array. It will write all of the x, then all of the y and lastly all of the z. If you want the same output, put it in a loop. Putting the above together, use:
do i=1, ArrayLen
WRITE(2, 100) x(i), y(i), z(i)
end do
100 format (3(2X,F18.16))
As a note, don't use single digit unit numbers, particularly the first few which conflict with system defined standard input/output/error units on most compilers.
This is a follow up to my get_command_argument() question.
I'm reading a command line argument (arg) into a Fortran program. Then I want to store the value of arg as an integer. ichar() doesn't do the job.
This seems kind of basic, so clearly I'm doing something wrong. Any hints?
program test_get_command_argument
integer :: i,j
character(len=32) :: arg
i = 0
do
call get_command_argument(i,arg)
if (LEN_TRIM(arg) == 0) EXIT
write (*,*) trim(arg)
i = i + 1
end do
j = ichar(arg)
end program
You want to use the "internal files" capability.
You should have a statement like read(arg,*) j.
This will read the character variable arg as if it were a file
and store the result into j.
This isn't an answer but an extended comment:
That's a bizarre way to loop over the command line arguments. What's wrong with the straightforward and obvious
do i = 1, command_argument_count()
call get_command_argument(i,arg)
! do funky stuff
end do