02-28-2020
A more detailed explanation follows.
The main awk code runs for each input line.
!a[$0]++ is ultra-condensed, quick and dirty.
A bit more explicit is !($0 in A) { A[$0]; print }:
If not $0 in array A (A[$0] not defined) then define A[$0] (no A[$0]=value needed here) and print $0.
The array A is associative (string-addressed). So if the same $0 will occur in another input line it will see a defined A[$0] and won't print.
If there is a pre-condition and no { action code } following then the default for a true condition is { print }, and print without arguments defaults to print $0.
Now to the quick and dirty !A[$0]++:
Define A[$0] with value 0 if undefined, if the negated value is non-zero (true) then default-print. Also post-increment A[$0].
If the same $0 will occur then the A[$0] value will be 1, negated 0 (false), won't print, but post-incremented.
If the same $0 will occur then the A[$0] value will be 2, negated 0 (false), won't print, but post-incremented.
...
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LEARN ABOUT OPENSOLARIS
print-service
print-service(1M) System Administration Commands print-service(1M)
NAME
print-service - select, report, import, export active print service on a system
SYNOPSIS
print-service [-s service [-m] | -q | -e file | -i file]
DESCRIPTION
The print-service utility manages print service selection, as well as export and import of basic print queue configuration.
Only a user root privileges or with the Printer Management profile can change the active print service or import print queue configuration.
OPTIONS
The following options are supported:
-s service
Select the active print service for on a host. service can be one of lp or cups.
-m
Migrate print queue configuration during print service selection.
-q
Report the active print service on a host.
-e file
Export basic print queue configuration to a file.
-i file
Import basic print queue configuration from a file.
EXAMPLES
Example 1 Selecting a Print Service
The following command selects the CUPS print service as the active print service on a host.
# print-service -s cups
Example 2 Reporting the Active Print Service
The following command reports the active print service on a host.
# print-service -q
Example 3 Exporting a Print Queue Configuration
The following command exports the print queue configuration from the active print service.
# print-service -e /tmp/queues
Example 4 Importing a Print Queue Configuration
The following command imports the print queue configuration to the active print service.
# print-service -i /tmp/queues
EXIT STATUS
0
Successful completion.
non-zero
An error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWpcu |
+-----------------------------+-----------------------------+
|Interface Stability |Obsolete |
+-----------------------------+-----------------------------+
SEE ALSO
intro(1), attributes(5)
NOTES
The print queue configuration saved and restored during export, import, and migration is limited to queue name and device name. It is
likely that further configuration changes will be required before imported or migrated print queues become usable.
SunOS 5.11 18 Mar 2008 print-service(1M)