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5.1.3 Extensions to namelist ¶

GNU Fortran fully supports the Fortran 95 standard for namelist I/O including array qualifiers, substrings and fully qualified derived types. The output from a namelist write is compatible with namelist read. The output has all names in upper case and indentation to column 1 after the namelist name. The following extensions are permitted:

• Old-style use of ‘$’ instead of ‘&’

  $MYNML
   X(:)%Y(2) = 1.0 2.0 3.0
   CH(1:4) = "abcd"
  $END
  

  It should be noted that the default terminator is ‘/’ rather than ‘&END’.

• Querying of the namelist when inputting from stdin. After at least one space, entering ‘?’ sends to stdout the namelist name and the names of the variables in the namelist:

   ?
  
  &mynml
   x
   x%y
   ch
  &end
  

  Entering ‘=?’ outputs the namelist to stdout, as if WRITE(*,NML = mynml) had been called:

  =?
  
  &MYNML
   X(1)%Y=  0.000000    ,  1.000000    ,  0.000000    ,
   X(2)%Y=  0.000000    ,  2.000000    ,  0.000000    ,
   X(3)%Y=  0.000000    ,  3.000000    ,  0.000000    ,
   CH=abcd,  /
  

  To aid this dialog, when input is from stdin, errors send their messages to stderr and execution continues, even if IOSTAT is set.

• PRINT namelist is permitted. This causes an error if -std=f95 is used.

  PROGRAM test_print
    REAL, dimension (4)  ::  x = (/1.0, 2.0, 3.0, 4.0/)
    NAMELIST /mynml/ x
    PRINT mynml
  END PROGRAM test_print
  

• Expanded namelist reads are permitted. This causes an error if -std=f95 is used. In the following example, the first element of the array is given the value 0.00 and the two succeeding elements are given the values 1.00 and 2.00.

  &MYNML
    X(1,1) = 0.00 , 1.00 , 2.00
  /
  

When writing a namelist, if no DELIM= is specified, by default a double quote is used to delimit character strings. With -std=f95 or later, the delim status is set to 'none'. Defaulting to quotes ensures that namelists with character strings can be subsequently read back in accurately.