Examples

   1.$ NAME = "PAOLO TESTA"
     $ FIRST = F$EXTRACT(0,5,NAME)
     $ SHOW SYMBOL FIRST
       FIRST = "PAOLO"

     This portion of a command procedure uses the F$EXTRACT function
     to extract the first 5 characters from the character string
     assigned to the symbol NAME. The offset and length arguments
     are integers, and the string argument is a symbol. You do not
     need to use quotation marks (" ")  around integers or symbols
     when they are used as arguments for lexical functions.

   2.$ P1 = "MYFILE.DAT"
     $ FILENAME = F$EXTRACT(0,F$LOCATE(".",P1),P1)

     This portion of a command procedure shows how to locate a
     character within a string, and how to extract a substring
     ending at that location.

     The lexical function F$LOCATE gives the numeric value
     representing the offset position of a period in the character
     string value of P1. (The offset position of the period is equal
     to the length of the substring before the period.)

     This F$LOCATE function is used as an argument in the F$EXTRACT
     function to specify the number of characters to extract from
     the string. If a procedure is invoked with the parameter
     MYFILE.DAT, these statements result in the symbol FILENAME
     being given the value MYFILE.

     Note that the F$LOCATE function in the above example assumes
     that the file specification does not contain a node name or
     a directory specification containing a subdirectory name. To
     obtain the file name from a full file specification, use the
     F$PARSE function.

   3.$ IF F$EXTRACT(12,2,F$TIME()) .GES. "12" THEN GOTO AFTERNOON
     $ MORNING:
     $ WRITE SYS$OUTPUT "Good morning!"
     $ EXIT
     $ AFTERNOON:
     $ WRITE SYS$OUTPUT "Good afternoon!"
     $ EXIT

     This example shows a procedure that displays a different
     message, depending on whether the current time is morning or
     afternoon. It first obtains the current time of day by using
     the F$TIME function. The F$TIME function returns a character
     string, which is the string argument for the F$EXTRACT
     function. The F$TIME function is automatically evaluated when
     it is used as an argument, so you do not need to use quotation
     marks.

     Next, the F$EXTRACT function extracts the hours from the date
     and time string returned by F$TIME. The string returned by
     F$TIME always contains the hours field beginning at an offset
     of 12 characters from the start of the string.

     The F$EXTRACT function extracts 2 characters from the string,
     beginning at this offset, and compares the string value
     extracted with the string value 12. If the comparison is true,
     then the procedure writes "Good afternoon!". Otherwise, it
     writes "Good morning!".

     Note that you can also use the F$CVTIME function to extract
     the hour field from a time specification. This method is easier
     than the one shown in the above example.