opening char variable data file

Hi all,

I am not sure why the following is not working, maybe someone will point out
the obvious to me ?

I set
file_name_use as WORK/aos__files.dat

indeed
write (*,*)"Opening ",file_name_use
does produce
Opening "WORK/aos__files.dat"

and
call system ("more "//file_name_use)
does
aos0412.all
AOS0412.ALL2
aos.430
bor53402.gps
bor53430.gps
bor53461.gps
..
..
..
which is correct

so, why does
open(unit=35,file=file_name_use)
give me
Fortran runtime error: No such file or directory
???

Anybody's guess?

Thank you.

G

.