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Top Forums UNIX for Beginners Questions & Answers Bash script, find the next closed (not in use) port from some port range. Post 303036750 by yossi on Wednesday 10th of July 2019 10:36:31 AM
Old 07-10-2019
Bash script, find the next closed (not in use) port from some port range.

hi,
i would like to create a bash script that check which port in my Linux server are closed (not in use) from a specific range, port range (3000-3010).
the print output need to be only 1 port, and it will be nice if the output will be saved as a variable or in same file.

my code is:
Code:
#!/bin/bash
IP=$1
first_port=$2
last_port=$3
function scanner

{
for ((port=$first_port; port<=$last_port; port++))
        do
                (echo >/dev/tcp/$IP/$port)> /dev/null 2>&1 && echo $port open || echo "$port closed"
        done
}

scanner

than to run it i use:
./demo2.sh 127.0.0.1 3000 3010

the output for this code is:
Quote:
3000 open
3001 open
3002 closed
3003 closed
3004 closed
3005 closed
3006 closed
3007 closed
3008 closed
3009 closed
3010 closed
the result that i am trying to get is only:
Quote:
3002
 

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CLOSE(7)						  PostgreSQL 9.2.7 Documentation						  CLOSE(7)

NAME
CLOSE - close a cursor SYNOPSIS
CLOSE { name | ALL } DESCRIPTION
CLOSE frees the resources associated with an open cursor. After the cursor is closed, no subsequent operations are allowed on it. A cursor should be closed when it is no longer needed. Every non-holdable open cursor is implicitly closed when a transaction is terminated by COMMIT or ROLLBACK. A holdable cursor is implicitly closed if the transaction that created it aborts via ROLLBACK. If the creating transaction successfully commits, the holdable cursor remains open until an explicit CLOSE is executed, or the client disconnects. PARAMETERS
name The name of an open cursor to close. ALL Close all open cursors. NOTES
PostgreSQL does not have an explicit OPEN cursor statement; a cursor is considered open when it is declared. Use the DECLARE(7) statement to declare a cursor. You can see all available cursors by querying the pg_cursors system view. If a cursor is closed after a savepoint which is later rolled back, the CLOSE is not rolled back; that is, the cursor remains closed. EXAMPLES
Close the cursor liahona: CLOSE liahona; COMPATIBILITY
CLOSE is fully conforming with the SQL standard. CLOSE ALL is a PostgreSQL extension. SEE ALSO
DECLARE(7), FETCH(7), MOVE(7) PostgreSQL 9.2.7 2014-02-17 CLOSE(7)
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