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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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semanage_port(3)					   Libsemanage API documentation					  semanage_port(3)

NAME
semanage_port - SELinux Network Ports Management API SYNOPSIS
#include <semanage/port_record.h> #include <semanage/ports_policy.h> #include <semanage/ports_local.h> This object contains properties associated with a range of network ports. For details on a specific function, see its manual page. Record API Overview semanage_port_create(3)- create a port range semanage_port_free(3)- release resources for this port range semanage_port_key_create(3)- create a key, which can be used to identify a port range semanage_port_key_free(3)- release resources for this port range key semanage_port_key_extract(3)- create a key matching this port range semanage_port_clone(3)- create an identical port range (deep-copy clone) semanage_port_compare(3)- compare this port range to the provided key semanage_port_compare2(3)- compare this port range to another Properties API Overview semanage_port_get_proto(3)- return the protocol for this port range semanage_port_get_proto_str(3)- return a string representation of the given port protocol semanage_port_set_proto(3)- set the protocol for this port range semanage_port_get_low(3)- return the low port number for this port range semanage_port_get_high(3)- return the high port number for this port range semanage_port_set_port(3)- set the port number (same low and high) for this port range semanage_port_set_range(3)- set the low and high port number for this port range semanage_port_get_con(3)- return the SELinux context for this port range semanage_port_set_con(3)- set the SELinux context for this port range Record Store API Overview semanage_port_modify_local(3)- add or update a port range in the local store semanage_port_del_local(3)- delete a port range from the local store semanage_port_exists(3)- check if a port range is defined in the persistent policy semanage_port_exists_local(3)- check if a port range is defined in the local store semanage_port_query(3)- query a port range in the persistent policy semanage_port_query_local(3)- query a port range in the local store semanage_port_count(3)- count the number of port ranges defined in the persistent policy semanage_port_count_local(3)- count the number of port ranges defined in the local store semanage_port_iterate(3)- execute a callback for each port range in the persistent policy semanage_port_iterate_local(3)- execute a callback for each port range in the local store semanage_port_list(3)- return an array containing all port ranges in the persistent policy semanage_port_list_local(3)- return an array containing all port ranges in the local store ivg2@cornell.edu 16 March 2006 semanage_port(3)
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