Provided by: pnetcdf-bin_1.10.0-3ubuntu1_amd64 bug

NAME

       ncmpigen - From a CDL file generate a netCDF file, a C program, or a Fortran program

SYNOPSIS

       ncmpigen [-b] [-c] [-f] [-n] [-o netcdf_filename] [-v file_format] input_file

DESCRIPTION

       ncmpigen  generates  either  a netCDF file, or C or Fortran source code to create a netCDF
       file.  The input to ncmpigen is a description of a netCDF file in a small  language  known
       as  CDL (network Common Data form Language), described below.  If no options are specified
       in invoking ncmpigen, it merely checks the syntax of the input CDL file,  producing  error
       messages  for  any  violations  of  CDL  syntax.   Other options can be used to create the
       corresponding netCDF file, to generate a C program that uses the  netCDF  C  interface  to
       create  the  netCDF  file,  or  to generate a Fortran program that uses the netCDF Fortran
       interface to create the same netCDF file.

       ncmpigen may be  used  with  the  companion  program  ncmpidump  to  perform  some  simple
       operations  on  netCDF  files.   For  example, to rename a dimension in a netCDF file, use
       ncmpidump to get a CDL version of the netCDF file, edit the CDL file to change the name of
       the dimensions, and use ncmpigen to generate the corresponding netCDF file from the edited
       CDL file.

OPTIONS

       -b     Create a (binary) netCDF file.  If the -o option is absent,  a  default  file  name
              will be constructed from the netCDF name (specified after the netcdf keyword in the
              input) by appending the `.nc'  extension.   If  a  file  already  exists  with  the
              specified name, it will be overwritten.

       -c     Generate  C  source  code  that  will  create  a  netCDF  file  matching the netCDF
              specification.  The C source code is written to standard output.

       -f     Generate Fortran source code that will create a netCDF  file  matching  the  netCDF
              specification.  The Fortran source code is written to standard output.

       -o netcdf_file
              Name  for  the binary netCDF file created.  If this option is specified, it implies
              the "-b" option.  (This option is necessary because netCDF files cannot be  written
              directly to standard output, since standard output is not seekable.)

       -n     Like  -b  option,  except  creates  netCDF  file with the obsolete `.cdf' extension
              instead of the `.nc' extension, in the absence of an output filename  specified  by
              the -o option.  This option is only supported for backward compatibility.

       -v file_format
              File  format  of  the  output  netCDF  file.  The value of file_format can be: 1 or
              classic for CDF-1 format.  2 or 64-bit-offset is CDF-2.  5 or  64-bit-variable  for
              CDF-5.  The default (if this option is not given) is CDF-1, the classic format.

EXAMPLES

       Check the syntax of the CDL file `foo.cdl':

              ncmpigen foo.cdl

       From the CDL file `foo.cdl', generate an equivalent binary netCDF file named `x.nc':

              ncmpigen -o x.nc foo.cdl

       From  the  CDL  file  `foo.cdl',  generate  a  C  program  containing  the netCDF function
       invocations necessary to create an equivalent binary netCDF file named `x.nc':

              ncmpigen -c -o x.nc foo.cdl

USAGE

   CDL Syntax Summary
       Below is an example of CDL syntax, describing a netCDF file with several named  dimensions
       (lat, lon, and time), variables (Z, t, p, rh, lat, lon, time), variable attributes (units,
       long_name, valid_range, _FillValue), and some data.  CDL keywords are in boldface.   (This
       example  is  intended to illustrate the syntax; a real CDL file would have a more complete
       set of attributes so that the data would be more completely self-describing.)

              netcdf foo {  // an example netCDF specification in CDL

              dimensions:
                   lat = 10, lon = 5, time = unlimited ;

              variables:
                   long    lat(lat), lon(lon), time(time);
                   float   Z(time,lat,lon), t(time,lat,lon);
                   double  p(time,lat,lon);
                   long    rh(time,lat,lon);

                   // variable attributes
                   lat:long_name = "latitude";
                   lat:units = "degrees_north";
                   lon:long_name = "longitude";
                   lon:units = "degrees_east";
                   time:units = "seconds since 1992-1-1 00:00:00";
                   Z:units = "geopotential meters";
                   Z:valid_range = 0., 5000.;
                   p:_FillValue = -9999.;
                   rh:_FillValue = -1;

              data:
                   lat   = 0, 10, 20, 30, 40, 50, 60, 70, 80, 90;
                   lon   = -140, -118, -96, -84, -52;
              }

       All CDL statements are terminated by a semicolon.  Spaces, tabs, and newlines can be  used
       freely for readability.  Comments may follow the characters `//' on any line.

       A  CDL  description  consists  of  three  optional parts: dimensions, variables, and data,
       beginning with the keyword dimensions:, variables:, and data, respectively.  The  variable
       part may contain variable declarations and attribute assignments.

       A  netCDF  dimension  is  used  to define the shape of one or more of the multidimensional
       variables contained in the netCDF file.  A netCDF dimension has a name  and  a  size.   At
       most  one  dimension  in a netCDF file can have the unlimited size, which means a variable
       using this dimension can grow to any length (like a record number in a file).

       A variable represents a multidimensional array of values of the same type.  A variable has
       a  name,  a data type, and a shape described by its list of dimensions.  Each variable may
       also have associated attributes (see below) as well as data values.  The name, data  type,
       and  shape of a variable are specified by its declaration in the variable section of a CDL
       description.  A variable may have the same name as  a  dimension;  by  convention  such  a
       variable   is  one-dimensional  and  contains  coordinates  of  the  dimension  it  names.
       Dimensions need not have corresponding variables.

       A netCDF attribute contains information about a netCDF variable or about the whole  netCDF
       dataset.  Attributes are used to specify such properties as units, special values, maximum
       and minimum valid values, scaling factors, offsets, and parameters.  Attribute information
       is represented by single values or arrays of values.  For example, "units" is an attribute
       represented by a character array such  as  "celsius".   An  attribute  has  an  associated
       variable,  a  name, a data type, a length, and a value.  In contrast to variables that are
       intended for data, attributes are intended for metadata (data about data).

       In CDL, an attribute is designated by a variable and attribute name, separated by `:'.  It
       is  possible to assign global attributes not associated with any variable to the netCDF as
       a whole by using `:' before the attribute name.  The data type of an attribute in  CDL  is
       derived  from  the  type  of  the value assigned to it.  The length of an attribute is the
       number of data values assigned to it, or the number of characters in the character  string
       assigned  to  it.   Multiple values are assigned to non-character attributes by separating
       the values with commas.  All values assigned to an attribute must be of the same type.

       The names for CDL dimensions, variables, and attributes  must  begin  with  an  alphabetic
       character or `_', and subsequent characters may be alphanumeric or `_' or `-'.

       The  optional  data  section  of  a  CDL  specification  is  where netCDF variables may be
       initialized.  The syntax of an initialization is simple: a variable name, an equals  sign,
       and  a comma-delimited list of constants (possibly separated by spaces, tabs and newlines)
       terminated with a semicolon.  For multi-dimensional  arrays,  the  last  dimension  varies
       fastest.   Thus  row-order rather than column order is used for matrices.  If fewer values
       are supplied than are needed to fill a variable, it  is  extended  with  a  type-dependent
       `fill  value',  which  can be overridden by supplying a value for a distinguished variable
       attribute named `_FillValue'.  The types of constants need not match the type declared for
       a  variable;  coercions  are done to convert integers to floating point, for example.  The
       constant `_' can be used to designate the fill value for a variable.

   Primitive Data Types
              char characters
              byte 8-bit data
              short     16-bit signed integers
              long 32-bit signed integers
              int  (synonymous with long)
              float     IEEE single precision floating point (32 bits)
              real (synonymous with float)
              double    IEEE double precision floating point (64 bits)

       Except for the added data-type byte and the  lack  of  unsigned,  CDL  supports  the  same
       primitive  data  types as C.  The names for the primitive data types are reserved words in
       CDL, so the names of variables, dimensions, and attributes must not  be  type  names.   In
       declarations, type names may be specified in either upper or lower case.

       Bytes  differ from characters in that they are intended to hold a full eight bits of data,
       and the zero byte has no special significance, as it does for  character  data.   ncmpigen
       converts  byte  declarations  to  char  declarations  in  the  output  C  code  and to the
       nonstandard BYTE declaration in output Fortran code.

       Shorts can hold values between -32768 and 32767.  ncmpigen converts short declarations  to
       short  declarations  in  the output C code and to the nonstandard INTEGER*2 declaration in
       output Fortran code.

       Longs can  hold  values  between  -2147483648  and  2147483647.   ncmpigen  converts  long
       declarations  to  long  declarations  in  the output C code and to INTEGER declarations in
       output Fortran  code.   int  and  integer  are  accepted  as  synonyms  for  long  in  CDL
       declarations.   Now  that  there are platforms with 64-bit representations for C longs, it
       may be better to use the int synonym to avoid confusion.

       Floats can hold values between about -3.4+38 and 3.4+38.  Their external representation is
       as  32-bit  IEEE  normalized  single-precision  floating point numbers.  ncmpigen converts
       float declarations to float declarations in the output C code and to REAL declarations  in
       output Fortran code.  real is accepted as a synonym for float in CDL declarations.

       Doubles can hold values between about -1.7+308 and 1.7+308.  Their external representation
       is as 64-bit IEEE standard normalized double-precision floating point  numbers.   ncmpigen
       converts  double  declarations  to  double declarations in the output C code and to DOUBLE
       PRECISION declarations in output Fortran code.

   CDL Constants
       Constants assigned to attributes or variables may be of any of  the  basic  netCDF  types.
       The  syntax  for  constants  is  similar  to  C  syntax, except that type suffixes must be
       appended to shorts and floats to distinguish them from longs and doubles.

       A byte constant is represented by a single character or multiple character escape sequence
       enclosed in single quotes.  For example,
               'a'           // ASCII `a'
               '\0'          // a zero byte
               '\n'          // ASCII newline character
               '\33'         // ASCII escape character (33 octal)
               '\x2b'        // ASCII plus (2b hex)
               '\377'        // 377 octal = 255 decimal, non-ASCII

       Character  constants  are enclosed in double quotes.  A character array may be represented
       as a string enclosed in double quotes.  The usual C string escape conventions are honored.
       For example
              "a"             // ASCII `a'
              "Two\nlines\n"  // a 10-character string with two embedded newlines
              "a bell:\007"   // a string containing an ASCII bell
       Note  that  the  netCDF  character array "a" would fit in a one-element variable, since no
       terminating NULL character is assumed.  However, a zero  byte  in  a  character  array  is
       interpreted  as  the end of the significant characters by the ncmpidump program, following
       the C convention.  Therefore, a NULL byte should not be embedded  in  a  character  string
       unless  at  the  end: use the byte data type instead for byte arrays that contain the zero
       byte.  NetCDF and CDL have no string type, but only fixed-length character  arrays,  which
       may be multi-dimensional.

       short  integer constants are intended for representing 16-bit signed quantities.  The form
       of a short constant is an integer constant with an  `s'  or  `S'  appended.   If  a  short
       constant  begins with `0', it is interpreted as octal, except that if it begins with `0x',
       it is interpreted as a hexadecimal constant.  For example:
              -2s      // a short -2
              0123s    // octal
              0x7ffs   //hexadecimal

       Long integer constants are intended for representing 32-bit signed quantities.   The  form
       of a long constant is an ordinary integer constant, although it is acceptable to append an
       optional `l' or `L'.  If a long constant begins with `0',  it  is  interpreted  as  octal,
       except that if it begins with `0x', it is interpreted as a hexadecimal constant.  Examples
       of valid long constants include:
              -2
              1234567890L
              0123i         // octal
              0x7ff         // hexadecimal

       Floating point constants of type float are appropriate  for  representing  floating  point
       data  with  about  seven significant digits of precision.  The form of a float constant is
       the same as a C floating point constant with an `f' or  `F'  appended.   For  example  the
       following are all acceptable float constants:
               -2.0f
               3.14159265358979f    // will be truncated to less precision
               1.f
               .

       Floating  point  constants  of type double are appropriate for representing floating point
       data with about sixteen significant digits of precision.  The form of a double constant is
       the  same  as  a  C floating point constant.  An optional `d' or `D' may be appended.  For
       example the following are all acceptable double constants:
              -2.0
              3.141592653589793
              1.0e-20
              1.d

DATE

       PNETCDF_RELEASE_DATE

BUGS

       The programs generated by ncmpigen when using the -c or -f use  initialization  statements
       to store data in variables, and will fail to produce compilable programs if you try to use
       them for large datasets, since the resulting statements may  exceed  the  line  length  or
       number of continuation statements permitted by the compiler.

       The CDL syntax makes it easy to assign what looks like an array of variable-length strings
       to a netCDF variable, but the strings will simply be concatenated into a single  array  of
       characters,  since  netCDF  cannot  represent  an  array of variable-length strings in one
       netCDF variable.

       NetCDF and CDL do not yet support a type corresponding to a 64-bit integer.