io - How to skip over an array in a Fortran unformatted file? -

io - How to skip over an array in a Fortran unformatted file? -

my programme reads “unformatted” file in fortran. among other things, file contains array programme not need, can quite large. skip array.

if programme writing data:

program write real :: useless(10), useful=42 open(123, file='foo', form='unformatted') write(123) size(useless) write(123) useless write(123) useful end programme write

then works reading:

program read integer :: n real, allocatable :: useless(:) real :: useful open(123, file='foo', form='unformatted') read(123) n allocate(useless(n)) read(123) useless read(123) useful print*, useful end programme read

but avoid allocating “useless” array. discovered this

program read2 integer :: n, real :: useless real :: useful open(123, file='foo', form='unformatted') read(123) n i=1,n read(123) useless end read(123) useful print*, useful end programme read2

does not work (because of record lengths beingness written file [edit, see francescalus' answer]).

it not alternative alter format of file.

it isn't sin read fewer file storage units in record.

program read real :: useful open(123, file='foo', form='unformatted') read(123) read(123) read(123) useful print*, useful end programme read

each "empty" read still advances record file connected sequential access.

as farther comment: sec effort doesn't fail "because of record lengths". fails because of effort read separate records. examples of significance of difference can found in many posts.

io fortran binaryfiles