# Special \$ Variables

> [HTML Version](special$variables.htm)

_Revised January 2024; see History_

The DO file processor supports various special information variables or built-in macros which  all have a \$ prefix, followed by one or more alphabetic characters and possibly an arithmetic suffix. The supported variables are listed here; those that are A-Shell extensions are noted at the end of the list.

Also note that the special \$ variables are only expanded within DO files, not CMD files.

| **Variable** | **Value** |
|------|------|
| \$: | Original device (e.g. "DSK0:") |
| \$P | Original ppn (e.g. "7,6") |
| \$\$ | Real dollar sign |
| \$TM | Time of day in 24 hour HH:MM format (e.g. "13:27") |
| \$TD | Current date in YYMMDD format |
| \$TW | Current day of week as a number (0=Mon, 1=Tue,...) |
| \$NJ | Current job name (e.g. "TSKAAA") |
| \$NT | Current terminal name |
| \$ND | Current terminal driver name |
| \$NS | Current OS (e.g. "AIX") |
| \$SV | Current OS version |
| \$UX | Current radix (e.g. "8" or "16") |
| \$LG | Current language (e.g. "ENGLISH") |
| \$LY | Yes character (e.g. "Y") |
| \$LN | No character (e.g. "N") |
| \$NU | Current login name (e.g. "root") |




The following are supported only under A-Shell:

| **Variable** | **Value** |
|------|------|
| \$HF | Current host full path (e.g. "/vm/miame/dsk0/001004") |
| \$HD | Current host disk (e.g. "/vm/miame/dsk0") |
| \$HP | Current host ppn (e.g. "001004") |
| \$HM | MIAME environmental variable definition (e.g. "/vm/miame") |
| \$MMDDYY\{+/-##\} | Each of these evaluates to current date in the specified format, with an optional +/- days adjustment. |
| \$DDMMYY\{+/-##\} | 
| \$YYMMDD\{+/-##\} | 

**Comments**

These special information variables are typically used in IF statements or in output messages.

Note that unlike ASB string symbols defined with the [DEFINE](define_compiler.md) statement, these special \$ variables in DO files do not contain their own quotes, so if they are used in a context that requires a quoted string, explicit quotes must be added.

**Examples**

IF "\$NU" = "jack"      ; (correct)

IF \$NU = jack          ; (incorrect)



IF LEFT("\$NJ",3) = "TAS"          ; (correct)

IF LEFT(\$NJ,3) = "TAS"            ; (incorrect)

IF "LEFT(\$NJ,3)" = "TAS"          ; (incorrect)



If today were December 1, 2023, then:

\$MMDDYY       equals     120123

\$MMDDYY+15    equals     121623

\$DDMMYY       equals     011223

\$DDMMYY-1     equals     301123

\$YYMMDD       equals     231201

\$YYMMDD+32    equals     240101



**History**

2024 January, A-Shell 7.0.1753:  Support added for date variables.