1.4 COMMAND SYNTAX

Commands in program Ferret conform to the following template:

COMM [/Q1/Q2...] [SUBCOM[/S1/S2...]] [ARG1 ARG2 ...] [!comment]

where

notes...

• The length of the command line is limited to a maximum of 2048 characters.
   
• Command lines ending with back slash are regarded as incomplete -- a special prompt is given to indicate that the next line is a continuation.
   
• In the documentation, items in square brackets are optional.  In commands themselves, square brackets modify a variable with information about the context (e.g the region, data set or transformation.)
   
• One or more spaces or tabs must separate the command from the subcommand and from each of the arguments. Spaces and tabs are optional preceding qualifiers.
   
• Multiple commands, separated by semicolons, can be given on the same line (e.g. yes? CANCEL DATA/ALL; CANCEL VAR/ALL).
   
• Command names, subcommand names, and qualifiers require at most 4 characters.
  (e.g., yes? CANCEL LIST/PRECISION is equivalent to yes? CANC LIST/PREC)
   
• Some qualifiers take an argument following "=" (e.g., yes? LIST/Y=10S:10N).
   
• An exclamation mark normally signifies the end of a command and the start of (optional) comment text.
   
• The backslash character (\), when placed directly before an exclamation point (!), apostrophe ('), semicolon (;), or forward slash (/), will hide it ("escape it") from Ferret.
   
• See the Expressions section for information on algebraic expressions as arguments to commands.
   
• See the Symbols sections for information on symbol substitution in commands.

Examples:

• A simple command and argument
  yes? LIST sst

   

• A comment on the command line
  yes? SET REGION/L=1/X=130:290/Y=-23:23 ! January in the Tropical Pacific

   

• Commands with qualifiers and arguments
  yes? VECTOR/L=30/COLOR=RED u,v
  yes? LET/UNITS=M ht = z[GZ=temp] - z0

   

• Subcommands
  yes? SET MODE METAFILE
  yes? SET REGION/X=130E:120W/J=20:40/Z=0/T=1-jan-1982:31-jan-1992

   

• Symbols used in a command. Note multiple commands on a line
  yes? DEFINE SYMBOL lower = -2; DEFINE SYMBOL upper = 6
  yes? SHADE/I=($lower):($upper) temp

   

• Use Square brackets to specify a variable's dataset or grid, range and optionally a delta- for the variable, or a transformation )
  yes? PLOT temp[X=180,L=1:50]
  or
  yes? LIST temp[X=130:200@AVE,L=1:50:5]
  or
  yes? LET/UNITS=M ht = z[GX=temp] - z0

   

• Immediate mode expression: enclosed in grave accents. (The expression must evaluate to a scalar, and is evaluated before the command is parsed or executed.)
  yes? CONTOUR/Z=`temp[X=180,Y=0,Z=@LOC:15]` salt

   

• A list of values (constant array) may be formed by enclosing values in curly brackets. For example in a function call:
  yes? LET aday = DAYS1900(1989,{3,6,9},1)

   

• Text for labels is enclosed in double quotes
  yes? VECTOR/TITLE="title_string" x_expr, y_expr

  If the string is to contain a quote, the backslash preserves it:
  yes? GO my_go_script "\"(-10,10,2)"\"
  sends the string "(-10,10,2)" to the script for more on go scripts