fdb-read¶

Read data from the FDB and write this data into a specified target file. This may involve visiting multiple databases if required by the request.

Usage¶

fdb-read request.mars target.grib
fdb-read --extract source.grib target.grib

Options¶

`--extract`	Extract the request(s) from an existing GRIB file
`--statistics`	Report timing statistics

Examples¶

Specify the [MARS request](MARS.md) in a plain text file. Note that this MARS request must be fully expanded. For example, it may not contain the /to/ or /by/ statements that the MARS client is able to expand.

% cat myrequest
retrieve,class=od,expver=0001,stream=oper,date=20151004,time=1200,domain=g,type=an,levtype=pl,step=0,levelist=700,param=155

# this will retrieve 2 fields
% fdb-read myrequest foo.grib
retrieve,class=od,date=20151004,domain=g,expver=0001,levelist=500/700,levtype=pl,param=155,step=0,stream=oper,time=1200,type=an
Compress handle: 3.3e-05 second elapsed, 3.2e-05 second cpu
Compress handle: 2e-06 second elapsed, 2e-06 second cpu
Read  rate: 4.7575 Gbytes per second
Write rate: 2.54081 Gbytes per second
Save into: 0.022224 second elapsed, 0.022182 second cpu

Obtain data from the FDB using the MARS request that would be implied by an existing GRIB file. In this example, foo.grib contains 2 fields that identify what needs to be retrieved.

% fdb-read --extract foo.grib out.grib
retrieve,class=od,date=20151004,domain=g,expver=0001,levelist=500,levtype=pl,param=155,step=0,stream=oper,time=1200,type=an
...
Compress handle: 3.3e-05 second elapsed, 3.2e-05 second cpu
Compress handle: 2e-06 second elapsed, 2e-06 second cpu
Read  rate: 4.7575 Gbytes per second
Write rate: 2.54081 Gbytes per second
Save into: 0.022224 second elapsed, 0.022182 second cpu