10.7 Input/output extensions [mostly 5.3]

• The NEWUNIT= specifier has been added to the OPEN statement; this allocates a new unit number that cannot clash with any other logical unit (the unit number will be a special negative value). For example,

        INTEGER unit
        OPEN(FILE='output.log',FORM='FORMATTED',NEWUNIT=unit)
        WRITE(unit,*) 'Logfile opened.'
  

  The NEWUNIT= specifier can only be used if either the FILE= specifier is also used, or if the STATUS= specifier is used with the value 'SCRATCH'.
• Recursive input/output is allowed on separate units. For example, in

     Write (*,Output_Unit) f(100)
  

  the function f is permitted to perform i/o on any unit except Output_Unit; for example, if the value 100 is out of range, it would be allowed to produce an error message with

     Write (*,Error_Unit) 'Error in F:',n,'is out of range'
  

• [6.0] A sub-format can be repeated an indefinite number of times by using an asterisk (*) as its repeat count. For example,

     SUBROUTINE s(x)
       LOGICAL x(:)
       PRINT 1,x
  1    FORMAT('x =',*(:,' ',L1))
     END SUBROUTINE
  

  will display the entire array x on a single line, no matter how many elements x has. An indefinite repeat count is only allowed at the top level of the format specification, and must be the last format item.
• [6.0] The G0 and G0.d edit descriptors perform generalised editing with all leading and trailing blanks (except those within a character value itself) omitted. For example,

     PRINT 1,1.25,.True.,"Hi !",123456789
  1  FORMAT(*(G0,','))
  

  produces the output

  1.250000,T,Hi !,123456789,
  

  [7.2] Note that G0.d was not permitted by Fortran 2008 to be used for output of types Integer, Logical, or Character data, but this limitation has been removed by Fortran 2018.