(!******************************************************
   Mosel User Guide Example Problems
   =================================

   file errio.mos
   ``````````````
   Handling I/O errors during "initializations".
   
  (c) 2011 Fair Isaac Corporation
      author: Y.Colombani, Aug. 2011, rev. May 2015
*******************************************************!)

model "IO error handling"
 uses 'mmsystem'

 parameters
  toread="errio.dat"
 end-parameters

 declarations
  a,b,c:dynamic array(range) of integer
 end-declarations

!******** Display counting information for a label ********
 procedure dispcnt(l:string)
  if getreadcnt(l)<1 then
   writeln("label '", l, "' has not been initialised")
  else
   writeln(getreadcnt(l), " item(s) read for label '", l, "'")
  end-if
 end-procedure
!**********************************************************

! Check whether the file we want to access exists
 if bittest(getfstat(toread),SYS_TYP)<>SYS_REG then
  writeln("File '", toread, "' does not exist or is not a regular file")
  exit(1)
 end-if

! Read input data with modified I/O controls to obtain info about what is read
 setparam("ioctrl", true)       ! Enable IO control by the model
 setparam("readcnt", true)      ! Enable per label counting (see 'getreadcnt')

 fopen("null:", F_ERROR)        ! Optional: Disable error stream

 initialisations from toread
  a b c
 end-initialisations
 
! Revert to default settings of controls
 setparam("readcnt", false)     
 setparam("ioctrl", false)
 
 fclose(F_ERROR)                ! Stop error redirection (re-enable default)

! Check for errors during reading
! - Since we have enabled "ioctrl" the model does not stop when an error occurs
!   during the initialization of data, it is therefore necessary to perform
!   our own test of the "iostatus".
! - If the error stream has been redirected to 'null' no error message gets
!   displayed by Mosel, without the redirection you should see a message.
 iostatus:=getparam("iostatus")
 if iostatus<>0 then
  writeln("Read failed")
  writeln("Total number of items read :", getparam("nbread"))
  dispcnt("a")
  dispcnt("b")
  dispcnt("c")
 end-if

end-model


With file 'errio.dat' as follows:
a:[(1) 1]
c:[(2) 2 (10) 5]

Output is:
>exe errio
Mosel: E-33: Initialization from file `errio.dat' failed for: `b'.
read failed
Total number of items read :3
1 item(s) read for label 'a'
label 'b' has not been initialised
2 item(s) read for label 'c'
Returned value: 0