getline Subroutine

public subroutine getline(unit, line, iostat, iomsg)


 getline(3f) - [M_io:READ] read a line of arbintrary length from specified
 LUN into allocatable string (up to system line length limit)


subroutine getline(unit,line,iostat,iomsg)

integer,intent(in)                       :: unit
character(len=:),allocatable,intent(out) :: line
integer,intent(out)                      :: iostat
character(len=:), allocatable, optional  :: iomsg


Read a line of any length up to programming environment maximum
line length. Requires Fortran 2003+.

It is primarily expected to be used when reading input which will
then be parsed or echoed.

The input file must have a PAD attribute of YES for the function
to work properly, which is typically true.

The simple use of a loop that repeatedly re-allocates a character
variable in addition to reading the input file one buffer at a
time could (depending on the programming environment used) be
inefficient, as it could reallocate and allocate memory used for
the output string with each buffer read.


LINE    The line read when IOSTAT returns as zero.
LUN     LUN (Fortran logical I/O unit) number of file open and ready
        to read.
IOSTAT  status returned by READ(IOSTAT=IOS). If not zero, an error
        occurred or an end-of-file or end-of-record was encountered.
IOMSG   error message returned by system when IOSTAT is not zero.


Sample program:

program demo_getline
use,intrinsic :: iso_fortran_env, only : stdin=>input_unit
use,intrinsic :: iso_fortran_env, only : iostat_end
use FPM_filesystem, only : getline
implicit none
integer :: iostat
character(len=:),allocatable :: line, iomsg
      call getline(stdin,line,iostat,iomsg)
      if(iostat /= 0) exit INFINITE
   enddo INFINITE
   if(iostat /= iostat_end)then
      write(*,*)'error reading input:',iomsg
end program demo_getline


Type IntentOptional Attributes Name
integer, intent(in) :: unit

Formatted IO unit

character(len=:), intent(out), allocatable :: line

Line to read

integer, intent(out) :: iostat

Status of operation

character(len=:), optional, allocatable :: iomsg

Error message

Source Code

subroutine getline(unit, line, iostat, iomsg)

    !> Formatted IO unit
    integer, intent(in) :: unit

    !> Line to read
    character(len=:), allocatable, intent(out) :: line

    !> Status of operation
    integer, intent(out) :: iostat

    !> Error message
    character(len=:), allocatable, optional :: iomsg

    integer, parameter :: BUFFER_SIZE = 1024
    character(len=BUFFER_SIZE)       :: buffer
    character(len=256)               :: msg
    integer :: size
    integer :: stat

    allocate(character(len=0) :: line)
        read(unit, '(a)', advance='no', iostat=stat, iomsg=msg, size=size) &
            & buffer
        if (stat > 0) exit
        line = line // buffer(:size)
        if (stat < 0) then
            if (is_iostat_eor(stat)) then
                stat = 0
            end if
        end if
    end do

    if (stat /= 0) then
        if (present(iomsg)) iomsg = trim(msg)
    end if
    iostat = stat

end subroutine getline