The GEMPAK user interface is text-based, case-insensitive, and handles many abbreviations and aliases. GEMPAK programs run as a command prompt and receive input either directly from the user or from a shell script.
The GEMPAK interface is organized by rows, with variables (SFFILE) first, then a short description (Surface data file), then the current settings ($GEMPAK/data/hrcbob.sfc):
vars description current setting ---- ----------- --------------- SFFILE Surface data file $GEMPAK/data/hrcbob.sfc AREA Data area WV DATTIM Date/time LAST SFPARM Surface parameter list SKYC;TMPF;WSYM;PMSL;;DWPF OUTPUT Output device/filename T IDNTYP STNM or STID STID
GEMPAK programs are started simply by typing their name in your terminal window:
> sflist
New values are assigned by entering the definitions directly:
GEMPAK-SFLIST>sffile = $GEMDATA/nmcbob.sfc
GEMPAK-SFLIST>area = den
GEMPAK-SFLIST>sfparm = tmpf;dwpf
Variables are listed with the command list or l for short:
GEMPAK-SFLIST>l
Programs are run with command run or r for short:
GEMPAK-SFLIST>r
Programs are exited with the command exit or e for short:
GEMPAK-SFLIST>e
To begin using the GEMPAK interface, start a programs such as sflist:
A list of all current values is followed by with a prompt on the last line. Type l to show the current definitions:
GEMPAK-SFLIST>l
SFFILE = $GEMPAK/data/hrcbob.sfc
AREA = WV
DATTIM = LAST
SFPARM = SKYC;TMPF;WSYM;PMSL;;DWPF;BRBK
OUTPUT = T
IDNTYP = STID
GEMPAK-SFLIST>
Run the programs with r:
GEMPAK-SFLIST>r
PARM = SKYC;TMPF;WSYM;PMSL;DWPF;BRBK
STN YYMMDD/HHMM SKYC TMPF WSYM PMSL DWPF BRBK
BKW 910820/0600 8.00 60.00 61.00 1011.00 59.00 4190.00
BLF 910820/0600 8.00 57.00 61.00 1010.60 56.00 4180.00
CRW 910820/0600 8.00 63.00 10.00 1011.20 62.00 3200.00
...
Parameters requested: SFFILE,AREA,DATTIM,SFPARM,OUTPUT,IDNTYP.
GEMPAK-SFLIST>
The parameters defined by SFPARM are displayed for DATTIM = LAST (0600 UTC) and stations which fall inside the area defined by AREA (in this case, an area centered around West Virginia).
After checking that the definition for SFFILE has observations to display, exit the program with the command e:
GEMPAK-SFLIST>e
While in the GEMPAK prompt (which you just exited, so start sflist again), you can view the help file for any program or parameter using the command phelp:
GEMPAK-SFLIST>phelp idntyp
IDNTYP
IDNTYP sets character or numeric station identifiers to be used for
input or output. The valid values are STID and STNM. STID specifies
station character identifiers; STNM specifies station numbers.
If the value in IDNTYP is not STNM, the default of STID will be used.
For example, to update station headers in SFSTNS:
IDNTYP = STID -- compares character ids in file with those
in the station table
IDNTYP = STNM -- compares numeric ids in file with those
in the station table
Back in the terminal window, list the files in the current working directory with ls -la and make note of two new files:
gemglb.nts stores values for all GEMPAK program variables, updated by the last program run, available by default to any GEMPAK program run next. A definition of SFFILE in sflist will be available in any other program which uses SFFILE (such as sfmap), as long as this file is available.last.nts stores values from the last program run, used the same as gemglb.nts but for the last program run.The default values for parameters such as SFFILE and SFPARM come from default files located in $GEMPAK/defaults/*.nts for each program.
Environment variables are used by GEMPAK to find needed executable, table, parameter, error, help, and map files without requiring user input.
$NAWIPS - Top of the NAWIPS distribution
$GEMPAK - Directory for the top of the GEMPAK tree
$GEMDATA - Location of data files
$OS_LIB - Library directory (used for installation)
$OS_BIN - Location of executable code
$GEMPDF - Location of parameter definition files
$GEMTBL - Location of tables
$GEMERR - Location of error messages
$GEMHLP - Location of on-line help files
$GEMMAPS - Location of map files
Each of these is defined in a variable definition file (~/NAWIPS/Gemenviron for csh/tcsh, ~/NAWIPS/Gemenviron.profile for bash). Depending on your shell, one of these files MUST be sourced in the current shell environment for GEMPAK programs to work.
source ~/NAWIPS/Gemenviron. ~/NAWIPS/Gemenviron.profileIf you're currently taking part in the Unidata GEMPAK Workshop, the above step has been taken care of for you by adding the source command to your .tcsh file, executed at login.
Check that the GEMPAK environmental variable are correct with the command:
env| grep GEMPAK