Differences

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--- dcl_symbols [2018/10/03 22:48] – add content lricker
+++ dcl_symbols [2018/10/23 19:41] – <code>...</code> tweaks lricker
@@ Line 12: / Line 12: @@
 DCL variables have **scope** (visibility):
-  * Global symbols, created/assigned with the **''==''** (or '':=='') operator, are visible at any level, including on the command line (level 0) and within executing command files (scripts, level 1 and higher/deeper).
+  * Global symbols, created/assigned with the **''==''** (or **'':==''**) operator, are visible at any level, including on the command line (level 0) and within executing command files (scripts, level 1 and higher/deeper).
-  * Local symbols, created/assigned with the ''='' (or '':='') operator, usually used and visible only within command files where created (and in nested command files).
+  * Local symbols, created/assigned with the **''=''** (or **'':=''**) operator, usually used and visible only within command files where created (and in nested command files).
 A DCL symbol can be used as a **command alias** -- the global variable's value is a string of characters, the first element or "word" of which is an executable DCL command; for example:
-  $ ls == "DIRECTORY /SIZE /DATE /PROTECTION"
+<code>
-  $ ls com:*.com;0
+$ ls == "DIRECTORY /SIZE /DATE /PROTECTION"
+$ ls com:*.com;0
-  Directory DSA2:[JSMITH.COM]
+Directory DSA2:[JSMITH.COM]
-  BELL.COM;2                         4  20-SEP-2017 09:41:19.35  (RWED,RWED,,)
-  ...
+BELL.COM;2                         4  20-SEP-2017 09:41:19.35  (RWED,RWED,,)
-  BUILD.COM;1                        1  26-JUL-1997 17:48:20.58  (RWED,RWED,RE,)
+...
-  CD.COM;1                           6   9-FEB-2016 08:51:05.90  (RWED,RWED,,)
+BUILD.COM;1                        1  26-JUL-1997 17:48:20.58  (RWED,RWED,RE,)
-  CLS.COM;10                         5  11-FEB-2016 10:41:25.45  (RWED,RWED,,)
+CD.COM;1                           6   9-FEB-2016 08:51:05.90  (RWED,RWED,,)
-  ...
+CLS.COM;10                         5  11-FEB-2016 10:41:25.45  (RWED,RWED,,)
+...
-  Total of 37 files, 247 blocks.
+Total of 37 files, 247 blocks.
+</code>
 A DCL variable can be used as a **counter** -- this example might be found in a command file (script):
-  $ count = 0   ! create and initialize
+<code>
-  $LOOP:
+$ count = 0   ! create and initialize
-  $ IF count .gt. 10 THEN GOTO LOOP_EXIT
+$LOOP:
-  $ WRITE sys$output "Loop iteration: ", count
+$ IF count .gt. 10 THEN GOTO LOOP_EXIT
-  $ count = count + 1
+$ WRITE sys$output "Loop iteration: ", count
-  $ GOTO LOOP
+$ count = count + 1
-  $LOOP_EXIT:
+$ GOTO LOOP
-  $ EXIT 1
+$LOOP_EXIT:
+$ EXIT 1
+</code>
 **Message strings** can be built-up (concatenated) using string variables:
-  $ Brother == "John"
+<code>
-  $ Sister  == "Jane"
+$ Brother == "John"
-  $ WRITE sys$output Sister, " & ", Brother, " are siblings."
+$ Sister  == "Jane"
-  Jane & John are siblings.
+$ WRITE sys$output Sister, " & ", Brother, " are siblings."
-  $ DELETE /SYMBOL /GLOBAL Sister
+Jane & John are siblings.
-  $ DELETE /SYMBOL /GLOBAL Brother
+$ DELETE /SYMBOL /GLOBAL Sister
+$ DELETE /SYMBOL /GLOBAL Brother
+</code>
 These examples only scratch the surface of what's possible with DCL variables.  The best places to learn more are to read existing command files, including your system's own SYS$SYLOGIN script, your own LOGIN.COM file, and various application or utility scripts that may be available.