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--- openvms:openvms-cheatsheet [2023/07/01 07:45] – dodger
+++ openvms:openvms-cheatsheet [2023/07/01 08:10] (current) – dodger
@@ Line 36: / Line 36: @@
 | ''-F-'' | ''4'' | SEVERE |
+====== Programming ======
+More or less
 ===== Symbols (Variables)  =====
 ^ Creation ^ Description ^
-| ''SYMBOL = <value> '' | Creates a **local** symbol (string or integer) |
+| ''SYMBOLNAME = <value> '' | Creates a **local** symbol (string or integer) |
-| ''SYMBOL == <value> '' | Creates a **global** symbol (string or integer) |
+| ''SYMBOLNAME == <value> '' | Creates a **global** symbol (string or integer) |
-| ''SYMBOL := <value> '' | Creates a **local** STRING symbol |
+| ''SYMBOLNAME := <value> '' | Creates a **local** STRING symbol |
-| ''SYMBOL :== <value> '' | Creates a **global** STRING symbol |
+| ''SYMBOLNAME :== <value> '' | Creates a **global** STRING symbol |
+| ''DELETE/SYMBOL SYMBOLNAME'' | Destroy local variable''SYMBOLNAME'' |
+| ''DELETE/SYMBOL/GLOBAL SYMBOLNAME'' | Destroy global variable ''SYMBOLNAME'' |
+| ''SHOW SYMBOL SYMBOLNAME'' | Show content of the variable ''SYMBOLNAME'' |
+===== Aliases through symbols =====
+Create an alias ''EDT'' with a frequently used command:
+<code DCL>
+EDT :== EDIT/EDT/COMMAND=SYS$LOGIN:EDTINI.DDT
+</code>
+Replace a command with the command you want:
+<code DCL>
+PRINT :== PRINT/NOBURST/NOFLAG/NOTRAILER/NOTIFY
+</code>
+This will replace the command ''PRINT'' with ''PRINT/NOBURST/NOFLAG/NOTRAILER/NOTIFY'' everytime you launch it.
+===== Operations with symbols =====
+==== Arithmetic operations (integers) ====
+<code DCL>
+$ APPLES = 10
+$ SHOW SYMBOL APPLES
+  APPLES = 10    Hex = 0000000A    Octal = 00000000012
+$ APPLES = 2 * (4+5)
+$ SHOW SYMBOL APPLES
+  APPLES = 18    Hex ...
+$ ORANGES = 15
+$ TOTAL_FRUIT = APPLES + ORANGES
+$ SHOW SYMBOL TOTAL_FRUIT
+  TOTAL_FRUIT = 33
+</code>
+=== List of operations ===
+^ Operation ^
+| ''+'' |
+| ''-'' |
+| ''*'' |
+| ''/'' |
+==== String operations ====
+<code DCL>
+$ APPLES = "Apples"
+$ SHOW SYMBOL APPLES
+  APPLES = "Apples"
+$ FRUIT = "Oranges and " + APPLES
+$ SHOW SYMBOL FRUIT
+  FRUIT = "Oranges and Apples"
+</code>
+==== Using subshells in commands ====
+Sub-shell is invoqued with ''2 SINGLE QUOTES+VARIABLE+1 SINGLE QUOTE'', for examples:
+<code DCL>
+$ FILETYPE = "login.com"
+$ TYPEIT = "TYPE ''filename'"
+$ SHOW SYMBOL TYPEIT
+  "TYPE login.com"
+</code>
+<WRAP center round tip 60%>
+Take care with string usage '':=''
+</WRAP>
+What works and what not (as a sub-shell):
+  * Works:
+<code DCL>
+$ FILETYPE := "login.com"
+$ TYPEIT := "TYPE ''filename'"
+$ SHOW SYMBOL TYPEIT
+  "TYPE login.com"
+</code>
+  * DON'T Work (as a literal)
+<code DCL>
+$ FILETYPE := "login.com"
+$ TYPEIT := "TYPE" +  filename
+$ SHOW SYMBOL TYPEIT
+  "TYPE FILENAME"
+</code>
+<WRAP center round tip 60%>
+In the other hand, without forcing string assignment
+</WRAP>
+Both are assigned as a variable:
+<code DCL>
+$ FILETYPE = "login.com"
+$ TYPEIT = "TYPE ''filename'"
+$ SHOW SYMBOL TYPEIT
+  "TYPE login.com"
+</code>
+<code DCL>
+$ FILETYPE = "login.com"
+$ TYPEIT = "TYPE" +  filename
+$ SHOW SYMBOL TYPEIT
+  "TYPE login.com"
+</code>
 ====== Startup ======