fortran - 如何删除 Fortran 文件中的特定行？

Question

我必须制作一个编辑待办事项列表的应用程序（文件 to_do.txt）。我可以阅读它，也可以添加新任务，但我无法删除文件的特​​定行而不破坏所有内容。我该怎么做？这是我的代码

 program compito4
        implicit none
        
        ! Declaring the variables
        integer :: unit, stat, counter, i
        character (len = 1) action
        character (len = 200) line, new_task
    
    
        ! Open the program
    
        open(newunit = unit, file = 'to_do.txt', status = 'OLD', position = 'APPEND')
        do
            print *, 'What would you like to do? (a)dd, (d)elete, (l)ist, (q)uit'
            read (*,*) action
            if (action == 'a') then
                print *, 'Insert the new task'
                read (*, '(A)') new_task
                write (unit, '(A)') '\n' // new_task    ! // is the string concatenation operator
                print *, 'New task successfully added'
            else if (action == 'd') then
                print *, 'Insert the number of the task to be removed'
                read (*,*) i
                print *, i
                counter = 0
                rewind unit
                do
                    read(unit, '(A)', iostat = stat) line
                    if (stat .ne. 0) then
                        backspace unit
                        exit
                    
                    else if (i == counter) then
                        print *, 'You are in the right spot'
                        print *, counter
                        backspace unit
                        write (unit, '(2A)') trim(line), ('->Task done')
                    end if
                    counter = counter + 1
                end do
            else if (action == 'l') then
                rewind unit
                counter = 0
                do
                    read(unit, '(A)', iostat = stat) line
                    if (stat .ne. 0) then        ! It handles the end of file!
                        backspace unit
                        exit
                    end if
                    print *, counter,') ', line
                    counter = counter + 1
            
                end do
            else if (action == 'q') then
                print *, 'Closing the program'
                exit
            else
                print *, 'Invalid choice'
            end if
        end do
    
        close(unit)
        
    
        
    end program compito4

标签： fortran