Package noaa.coastwatch.tools

Class hdatt

java.lang.Object

noaa.coastwatch.tools.hdatt

public final class hdatt
extends Object

The attribute tool reads and writes HDF file attributes.

Name

hdatt - reads or writes HDF file attributes.

Synopsis

hdatt [OPTIONS] input

Options:

-h, --help
-n, --name=STRING
-t, --type=TYPE
-l, --value=STRING1[/STRING2/...]
-V, --variable=STRING
--version

Description

The attribute tool reads or writes HDF file attributes using the HDF Scientific Data Sets (SDS) interface. The two modes work as follows:

Read mode

In read mode, the tool can read from either the global attribute set (the default), or the attribute set specific to a variable (when then --variable option is specified). It can read either all attribute values in the set (the default), or just a single attribute value (when the --name option is specified).

Write mode

Write mode is specified by the use of the --value option, which provides a value for a named attribute. In write mode, the user is required to supply an attribute name and value, and optionally a type. If no type is specified, the type defaults to 'string' (see the --type option below for the meanings of various type names). Attributes may be written to the global attribute set (the default), or to specific variables in the data file using the --variable option.

Note: The attribute tool is currently limited to reading and writing only the signed HDF data types. In read mode, unsigned HDF attribute data are read correctly, but the value displayed as if it were signed.

Parameters

Main parameters:

input

The input data file name.

Options:

-n, --name=STRING

The name of the attribute to read or write.

-t, --type=TYPE

The attribute data type (write mode only). The valid types and their HDF equivalents are as follows:

Attribute Types

Type name	HDF type
string	DFNT_CHAR8
byte	DFNT_INT8
short	DFNT_INT16
int	DFNT_INT32
long	DFNT_INT64
float	DFNT_FLOAT32
double	DFNT_FLOAT64

-l, --value=STRING1[/STRING2/...]

The value(s) for the named attribute. If specified, this places the tool into write mode, and --name must specify an attribute name. If an attribute already exists, its value is overwritten with the new value. If an attribute with the name does not exist, it is created and the new value assigned to it. By default if this option is not used, the tool is in read mode.

-V, --variable=STRING

The variable to read or write the attribute data. By default, the attribute is read from or written to the global attribute set.

--version

Prints the software version.

Exit status

0 on success, > 0 on failure. Possible causes of errors:

• Invalid command line option
• Invalid input or output file names
• Invalid variable name
• Invalid attribute name in read mode
• Invalid attribute type in write mode
• Value does not convert to the specified attribute data type

Examples

As an example of read mode, the following command reads and prints all the global attribute data from a CoastWatch HDF file:

   phollema$ hdatt 2005_095_1522_n17_er.hdf

   satellite = noaa-17
   sensor = avhrr
   origin = USDOC/NOAA/NESDIS CoastWatch
   cwhdf_version = 3.2
   pass_type = day
   pass_date = 12878
   start_time = 55371.0
   projection_type = mapped
   projection = Mercator
   gctp_sys = 5
   gctp_zone = 0
   gctp_parm = 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
   gctp_datum = 12
   et_affine = 0.0 -1470.0 1470.0 0.0 -8804259.100925786 5723777.271647277
   rows = 1401
   cols = 1302
   polygon_latitude = 45.83810150571052 45.83810150571052 45.83810150571052 
     45.83810150571052 45.83810150571052 42.51315402540104 38.99999999998719 
     35.30179546333813 31.424886223357582 31.424886223357582 31.424886223357582 
     31.424886223357582 31.424886223357582 35.30179546333813 38.99999999998719 
     42.51315402540104 45.83810150571052
   polygon_longitude = -79.09000515710031 -74.79500257855015 -70.5 -66.20499742144985 
     -61.90999484289969 -61.90999484289969 -61.90999484289969 -61.90999484289969 
     -61.90999484289969 -66.20499742144985 -70.5 -74.79500257855015 -79.09000515710031 
     -79.09000515710031 -79.09000515710031 -79.09000515710031 -79.09000515710031
   history = cwimport product.tshdf product.hdf
 

To dump only a single attribute:

   phollema$ hdatt --name satellite 2005_095_1522_n17_er.hdf

   noaa-17
 

or a single attribute from a specific variable:

   phollema$ hdatt --name units --variable avhrr_ch3a 2005_095_1522_n17_er.hdf

   albedo*100%
 

As an example of write mode, suppose that we wanted to save the date when the file was originally downloaded from the server:

   phollema$ hdatt --name download_date --value "Mon Apr 11 18:20:15 PDT 2005" 
     2005_095_1522_n17_er.hdf
 

Now suppose we wanted to assign an integer quality value of 65% to the file based on some test that was performed on the file data:

   phollema$ hdatt --name quality_value --value 65 --type int 2005_095_1522_n17_er.hdf
 

Finally, suppose that we wanted to change the units and scaling factor / offset of a variable, originally in degrees Celsius and scaled by 0.01, to degrees Fahrenheit:

   phollema$ hdatt --name units --value "deg F" --variable sst 2005_095_1522_n17_er.hdf
   phollema$ hdatt --name scale_factor --value 0.018 --type double --variable sst 
     2005_095_1522_n17_er.hdf
   phollema$ hdatt --name add_offset --value -1777.777777 --type double --variable sst 
     2005_095_1522_n17_er.hdf
 

Since:

3.2.0

Author:

Peter Hollemans

Method Summary

Modifier and Type	Method	Description
static void	main(String[] argv)	Performs the main function.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

main

public static void main(String[] argv)

Performs the main function.

Parameters:

argv - the list of command line parameters.