getline(3f) - [M_io:READ] read a line of arbintrary length from specified
LUN into allocatable string (up to system line length limit)
(LICENSE:PD)
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
open(unit=stdin,pad='yes')
INFINITE: do
call getline(stdin,line,iostat,iomsg)
if(iostat /= 0) exit INFINITE
write(*,'(a)')'['//line//']'
enddo INFINITE
if(iostat /= iostat_end)then
write(*,*)'error reading input:',iomsg
endif
end program demo_getline
| Type | Intent | Optional | 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 |
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 = 32768
character(len=BUFFER_SIZE) :: buffer
character(len=256) :: msg
integer :: size
integer :: stat
allocate(character(len=0) :: line)
do
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
exit
end if
end do
if (stat /= 0) then
if (present(iomsg)) iomsg = trim(msg)
end if
iostat = stat
end subroutine getline