String

A string is a data type in OpenVMS that represents a sequence of ASCII characters. Here is a symbol that has a string type:

$ TEST == "This is a string symbol"
$ SHOW SYMBOL TEST
  TEST == "This is a string symbol"
 

To label a sequence of characters as a string, put it in double quotes.

String Operations

The following string operations are possible:

• string concatenation:

$ a = "This is a "
$ b = "string"
$ c = a + b
$ show sym c
  C = "This is a string"
 

• string subtraction (works for the first substring located inside of the string):

3$ d = c-"a"
SMAN43$ show sym d
  D = "This is  string"
 

• locating substrings in a string (with F$LOCATE()):

$ WRITE SYS$OUTPUT F$LOCATE("E","HELLO")
1
 

• obtaining string length (with F$LENGTH()):

$ WRITE SYS$OUTPUT F$LENGTH("HELLO")
5
 

• extracting a substring from a string (with F$EXTRACT()):

$ WRITE SYS$OUTPUT F$EXTRACT("1",2,"HELLO")
EL
 

• extracting an element from a string with delimiters (with F$ELEMENT()):

$ WRITE SYS$OUTPUT F$ELEMENT(0,"/","1/2/3")
1
 

• changing string case with F$EDIT():

$ a = "HeLlO"
$  write sys$output f$edit(a,"UPCASE")
HELLO
$ write sys$output f$edit(a,"LOWERCASE")
hello
 

• removing double spaces from a string:

SMAN43$ a = "           hello     there"
SMAN43$ write sys$output f$edit(a,"compress")
 hello there
 

• removing all spaces from a string:

SMAN43$ a = "           hello     there"
SMAN43$ write sys$output f$edit(a,"collapse")
hellothere
 

• removing comments from a string:

$ a = "Hello! How can I help?"
$ write sys$output f$edit(a,"uncomment")
Hello
 

• formatting a string with F$FAO()
• wilcard matching with F$MATCH_WILD()

Strings vs Integers

You can convert an integer into a string with F$STRING(). To convert a string into an integer, use F$INTEGER(). If the string being converted to an integer consists of numbers, it will be converted to that number:

SMAN43$ a = "12"
SMAN43$ b = f$integer(a)
SMAN43$ show sym b
  B = 12   Hex = 0000000C  Octal = 00000000014
 

If it contains alphanumeric characters, the evaluation of the Boolean value is used: all strings beginning with "Y" or "y" are evaluated as 1 and all other strings as 0:

SMAN43$ a = "a12"
SMAN43$ b = f$integer(a)
SMAN43$ show sym b
  B = 0   Hex = 00000000  Octal = 00000000000
 

String Symbols

To define a string symbol, you can use either a colon (:) before the equals sign or the double quotes (") around the equivalence string. The difference is that the quotes preserve the case of the string and the colon does not:

SMAN43$ a := Hello
SMAN43$ show sym a
  A = "HELLO"
SMAN43$ a = "Hello"
SMAN43$ show sym a
  A = "Hello"
 

Literal Quotes

To put double quotes inside of a string, use two sets of double quotes:

$ a = "Here are some ""quotes"" for you"
$ show sym a
  A = "Here are some "quotes" for you"
 

A single double quote (") symbol can be defined like this:

$ a = """"
$ show sym a
  A = """
 

To put single quotes inside of a string, define a symbol for a single quote and then concatenate that with the other strings:

$ a = "'"
$ show sym a
  A = "'"
$ b = "Here are some "+a+"single quotes"+a+" for you"
$ show sym b
  B = "Here are some 'single quotes' for you"
 

The reason you cannot just put single quotes inside of a string is that they are used to force symbol substitution inside of a string.