I have task to create quite complicated bash script, which at first part is checking the connection to host:port with telnet and- if telnet would fail or would not be installed, try the connection using netcat.
I have problem with loop, where it will skip netcat if telnet would connect to the host and also, if both- telnet and netcat would fail- script would finish with error message.
The script:
#!/bin/bash
echo Type host IP address
read REMOTEHOST
echo Type port number
read REMOTEPORT
TIMEOUT=5
echo quit | timeout --signal=9 5 telnet $REMOTEHOST $REMOTEPORT
if nc -w $TIMEOUT -z $REMOTEHOST $REMOTEPORT; then
echo "I was able to connect to ${REMOTEHOST}:${REMOTEPORT}"
else
echo "Connection to ${REMOTEHOST}:${REMOTEPORT} failed. Exit code from Netcat was ($?)."
fi
You can use the $? variable to get the exit code from the last command.
I found that your original telnet command exits with error code 1 on my system because the escape character is ^]. When I telnet manually I need to hit ctrl-] to enter the telnet prompt, then I can enter 'quit'.
The trick here is you cannot just type ^], you have to type ctrl-v ctrl-]
ctrl-v tells the system to capture the next ctrl character.
The following gives me an exit code of 0, and you can verify by running it manually with echo $? at the command line
-- remember to use ctrl-v ctr-]
$ (echo ^]; echo quit) | timeout --signal=9 5 telnet <REMOTEHOST> <REMOTEPORT>
$ echo $?
Then you can use this in your script:
#!/bin/bash
echo Type host IP address
read REMOTEHOST
echo Type port number
read REMOTEPORT
TIMEOUT=5
(echo ^]; echo quit) | timeout --signal=9 5 telnet $REMOTEHOST $REMOTEPORT > /dev/null 2>&1
TELNET_EXIT_CODE=$?
if [[ $TELNET_EXIT_CODE -ne 0 ]]; then
nc -w $TIMEOUT -z $REMOTEHOST $REMOTEPORT > /dev/null 2>&1
NC_EXIT_CODE=$?
fi
if [[ $TELNET_EXIT_CODE -eq 0 ]] || [[ $NC_EXIT_CODE -eq 0 ]]; then
echo "success"
else
echo "fail"
fi
Tested on Ubuntu 20.04.04, GNU bash version 5.0.17, Telnet version 0.17-41
I have following IP in a server
192.168.1.1
192.168.1.2
192.168.1.3
192.168.1.4
I need to know if those IP are being used or not?
I could find using lsof but it's too slow
for ip in ${server_ip_list[#]}; do
lsof -i #$ip &>/dev/null && echo "$ip is used" || echo "$ip is unused"
done
Below command is faster but I need to specify port and protocol
true &>/dev/null </dev/tcp/192.168.1.1/80 && echo used || echo unused
I'm looking for a faster command using which I can determine if the IP is used regardless of protocol or port.
I'd appreciate if anyone could help with a solution or links where I can read about it.
Maybe you could use command ping to check if specific ip is being used (not disable ICMP in firewall). If you think for or while loop operation is too slow, you could try to use command parallel to execute command simultaneously.
Code sample like
ip_check(){
ip="$1"
ping -c 1 -W 1 "$ip" &> /dev/null
if [[ $? -eq 0 ]]; then
echo 'used'
else
echo 'unused'
fi
}
export -f ip_check
cat ip_file.txt | parallel -k -j 0 ip_check 2> /dev/null
I'm looking for a quick and simple method for properly testing if a given TCP port is open on a remote server, from inside a Shell script.
I've managed to do it with the telnet command, and it works fine when the port is opened, but it doesn't seem to timeout when it's not and just hangs there...
Here's a sample:
l_TELNET=`echo "quit" | telnet $SERVER $PORT | grep "Escape character is"`
if [ "$?" -ne 0 ]; then
echo "Connection to $SERVER on port $PORT failed"
exit 1
else
echo "Connection to $SERVER on port $PORT succeeded"
exit 0
fi
I either need a better way, or a way to force telnet to timeout if it doesn't connect in under 8 seconds for example, and return something I can catch in Shell (return code, or string in stdout).
I know of the Perl method, which uses the IO::Socket::INET module and wrote a successful script that tests a port, but would rather like to avoid using Perl if possible.
Note: This is what my server is running (where I need to run this from)
SunOS 5.10 Generic_139556-08 i86pc i386 i86pc
As pointed by B. Rhodes, nc (netcat) will do the job. A more compact way to use it:
nc -z <host> <port>
That way nc will only check if the port is open, exiting with 0 on success, 1 on failure.
For a quick interactive check (with a 5 seconds timeout):
nc -z -v -w5 <host> <port>
It's easy enough to do with the -z and -w TIMEOUT options to nc, but not all systems have nc installed. If you have a recent enough version of bash, this will work:
# Connection successful:
$ timeout 1 bash -c 'cat < /dev/null > /dev/tcp/google.com/80'
$ echo $?
0
# Connection failure prior to the timeout
$ timeout 1 bash -c 'cat < /dev/null > /dev/tcp/sfsfdfdff.com/80'
bash: sfsfdfdff.com: Name or service not known
bash: /dev/tcp/sfsfdfdff.com/80: Invalid argument
$ echo $?
1
# Connection not established by the timeout
$ timeout 1 bash -c 'cat < /dev/null > /dev/tcp/google.com/81'
$ echo $?
124
What's happening here is that timeout will run the subcommand and kill it if it doesn't exit within the specified timeout (1 second in the above example). In this case bash is the subcommand and uses its special /dev/tcp handling to try and open a connection to the server and port specified. If bash can open the connection within the timeout, cat will just close it immediately (since it's reading from /dev/null) and exit with a status code of 0 which will propagate through bash and then timeout. If bash gets a connection failure prior to the specified timeout, then bash will exit with an exit code of 1 which timeout will also return. And if bash isn't able to establish a connection and the specified timeout expires, then timeout will kill bash and exit with a status of 124.
TOC:
Using bash and timeout
Command
Examples
Using nc
Command
RHEL 6 (nc-1.84)
Installation
Examples
RHEL 7 (nmap-ncat-6.40)
Installation
Examples
Remarks
Using bash and timeout:
Note that timeout should be present with RHEL 6+, or is alternatively found in GNU coreutils 8.22. On MacOS, install it using brew install coreutils and use it as gtimeout.
Command:
$ timeout $TIMEOUT_SECONDS bash -c "</dev/tcp/${HOST}/${PORT}"; echo $?
If parametrizing the host and port, be sure to specify them as ${HOST} and ${PORT} as is above. Do not specify them merely as $HOST and $PORT, i.e. without the braces; it won't work in this case.
Example:
Success:
$ timeout 2 bash -c "</dev/tcp/canyouseeme.org/80"; echo $?
0
Failure:
$ timeout 2 bash -c "</dev/tcp/canyouseeme.org/81"; echo $?
124
If you must preserve the exit status of bash,
$ timeout --preserve-status 2 bash -c "</dev/tcp/canyouseeme.org/81"; echo $?
143
Using nc:
Note that a backward incompatible version of nc gets installed on RHEL 7.
Command:
Note that the command below is unique in that it is identical for both RHEL 6 and 7. It's just the installation and output that are different.
$ nc -w $TIMEOUT_SECONDS -v $HOST $PORT </dev/null; echo $?
RHEL 6 (nc-1.84):
Installation:
$ sudo yum install nc
Examples:
Success:
$ nc -w 2 -v canyouseeme.org 80 </dev/null; echo $?
Connection to canyouseeme.org 80 port [tcp/http] succeeded!
0
Failure:
$ nc -w 2 -v canyouseeme.org 81 </dev/null; echo $?
nc: connect to canyouseeme.org port 81 (tcp) timed out: Operation now in progress
1
If the hostname maps to multiple IPs, the above failing command will cycle through many or all of them. For example:
$ nc -w 2 -v microsoft.com 81 </dev/null; echo $?
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
1
RHEL 7 (nmap-ncat-6.40):
Installation:
$ sudo yum install nmap-ncat
Examples:
Success:
$ nc -w 2 -v canyouseeme.org 80 </dev/null; echo $?
Ncat: Version 6.40 ( http://nmap.org/ncat )
Ncat: Connected to 52.202.215.126:80.
Ncat: 0 bytes sent, 0 bytes received in 0.22 seconds.
0
Failure:
$ nc -w 2 -v canyouseeme.org 81 </dev/null; echo $?
Ncat: Version 6.40 ( http://nmap.org/ncat )
Ncat: Connection timed out.
1
If the hostname maps to multiple IPs, the above failing command will cycle through many or all of them. For example:
$ nc -w 2 -v microsoft.com 81 </dev/null; echo $?
Ncat: Version 6.40 ( http://nmap.org/ncat )
Ncat: Connection to 104.43.195.251 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection to 23.100.122.175 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection to 23.96.52.53 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection to 191.239.213.197 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection timed out.
1
Remarks:
The -v (--verbose) argument and the echo $? command are of course for illustration only.
With netcat you can check whether a port is open like this:
nc my.example.com 80 < /dev/null
The return value of nc will be success if the TCP port was opened, and failure (typically the return code 1) if it could not make the TCP connection.
Some versions of nc will hang when you try this, because they do not close the sending half of their socket even after receiving the end-of-file from /dev/null. On my own Ubuntu laptop (18.04), the netcat-openbsd version of netcat that I have installed offers a workaround: the -N option is necessary to get an immediate result:
nc -N my.example.com 80 < /dev/null
In Bash using pseudo-device files for TCP/UDP connections is straight forward. Here is the script:
#!/usr/bin/env bash
SERVER=example.com
PORT=80
</dev/tcp/$SERVER/$PORT
if [ "$?" -ne 0 ]; then
echo "Connection to $SERVER on port $PORT failed"
exit 1
else
echo "Connection to $SERVER on port $PORT succeeded"
exit 0
fi
Testing:
$ ./test.sh
Connection to example.com on port 80 succeeded
Here is one-liner (Bash syntax):
</dev/tcp/localhost/11211 && echo Port open. || echo Port closed.
Note that some servers can be firewall protected from SYN flood attacks, so you may experience a TCP connection timeout (~75secs). To workaround the timeout issue, try:
timeout 1 bash -c "</dev/tcp/stackoverflow.com/81" && echo Port open. || echo Port closed.
See: How to decrease TCP connect() system call timeout?
I needed a more flexible solution for working on multiple git repositories so I wrote the following sh code based on 1 and 2. You can use your server address instead of gitlab.com and your port in replace of 22.
SERVER=gitlab.com
PORT=22
nc -z -v -w5 $SERVER $PORT
result1=$?
#Do whatever you want
if [ "$result1" != 0 ]; then
echo 'port 22 is closed'
else
echo 'port 22 is open'
fi
check ports using bash
Example
$ ./test_port_bash.sh 192.168.7.7 22
the port 22 is open
Code
HOST=$1
PORT=$2
exec 3> /dev/tcp/${HOST}/${PORT}
if [ $? -eq 0 ];then echo "the port $2 is open";else echo "the port $2 is closed";fi
If you're using ksh or bash they both support IO redirection to/from a socket using the /dev/tcp/IP/PORT construct. In this Korn shell example I am redirecting no-op's (:) std-in from a socket:
W$ python -m SimpleHTTPServer &
[1] 16833
Serving HTTP on 0.0.0.0 port 8000 ...
W$ : </dev/tcp/127.0.0.1/8000
The shell prints an error if the socket is not open:
W$ : </dev/tcp/127.0.0.1/8001
ksh: /dev/tcp/127.0.0.1/8001: cannot open [Connection refused]
You can therefore use this as the test in an if condition:
SERVER=127.0.0.1 PORT=8000
if (: < /dev/tcp/$SERVER/$PORT) 2>/dev/null
then
print succeeded
else
print failed
fi
The no-op is in a subshell so I can throw std-err away if the std-in redirection fails.
I often use /dev/tcp for checking the availability of a resource over HTTP:
W$ print arghhh > grr.html
W$ python -m SimpleHTTPServer &
[1] 16863
Serving HTTP on 0.0.0.0 port 8000 ...
W$ (print -u9 'GET /grr.html HTTP/1.0\n';cat <&9) 9<>/dev/tcp/127.0.0.1/8000
HTTP/1.0 200 OK
Server: SimpleHTTP/0.6 Python/2.6.1
Date: Thu, 14 Feb 2013 12:56:29 GMT
Content-type: text/html
Content-Length: 7
Last-Modified: Thu, 14 Feb 2013 12:55:44 GMT
arghhh
W$
This one-liner opens file descriptor 9 for reading from and writing to the socket, prints the HTTP GET to the socket and uses cat to read from the socket.
While an old question, I've just dealt with a variant of it, but none of the solutions here were applicable, so I found another, and am adding it for posterity. Yes, I know the OP said they were aware of this option and it didn't suit them, but for anyone following afterwards it might prove useful.
In my case, I want to test for the availability of a local apt-cacher-ng service from a docker build. That means absolutely nothing can be installed prior to the test. No nc, nmap, expect, telnet or python. perl however is present, along with the core libraries, so I used this:
perl -MIO::Socket::INET -e 'exit(! defined( IO::Socket::INET->new("172.17.42.1:3142")))'
In some cases where tools like curl, telnet, nc o nmap are unavailable you still have a chance with wget
if [[ $(wget -q -t 1 --spider --dns-timeout 3 --connect-timeout 10 host:port; echo $?) -eq 0 ]]; then echo "OK"; else echo "FAIL"; fi
If you want to use nc but don't have a version that support -z, try using --send-only:
nc --send-only <IP> <PORT> </dev/null
and with timeout:
nc -w 1 --send-only <IP> <PORT> </dev/null
and without DNS lookup if it's an IP:
nc -n -w 1 --send-only <IP> <PORT> </dev/null
It returns the codes as the -z based on if it can connect or not.
Building on the most highly voted answer, here is a function to wait for two ports to be open, with a timeout as well. Note the two ports that mus be open, 8890 and 1111, as well as the max_attempts (1 per second).
function wait_for_server_to_boot()
{
echo "Waiting for server to boot up..."
attempts=0
max_attempts=30
while ( nc 127.0.0.1 8890 < /dev/null || nc 127.0.0.1 1111 < /dev/null ) && [[ $attempts < $max_attempts ]] ; do
attempts=$((attempts+1))
sleep 1;
echo "waiting... (${attempts}/${max_attempts})"
done
}
I needed short script which was run in cron and hasn't output. I solve my trouble using nmap
open=`nmap -p $PORT $SERVER | grep "$PORT" | grep open`
if [ -z "$open" ]; then
echo "Connection to $SERVER on port $PORT failed"
exit 1
else
echo "Connection to $SERVER on port $PORT succeeded"
exit 0
fi
To run it You should install nmap because it is not default installed package.
I'm guessing that it's too late for an answer, and this might not be a good one, but here you go...
What about putting it inside of a while loop with a timer on it of some sort. I'm more of a Perl guy than Solaris, but depending on the shell you're using, you should be able to do something like:
TIME = 'date +%s' + 15
while TIME != `date +%s'
do whatever
And then just add a flag in the while loop, so that if it times out before completing, you can cite the timeout as reason for failure.
I suspect that the telnet has a timeout switch as well, but just off the top of my head, I think the above will work.
This uses telnet behind the scenes, and seems to work fine on mac/linux. It doesn't use netcat because of the differences between the versions on linux/mac, and this works with a default mac install.
Example:
$ is_port_open.sh 80 google.com
OPEN
$ is_port_open.sh 8080 google.com
CLOSED
is_port_open.sh
PORT=$1
HOST=$2
TIMEOUT_IN_SEC=${3:-1}
VALUE_IF_OPEN=${4:-"OPEN"}
VALUE_IF_CLOSED=${5:-"CLOSED"}
function eztern()
{
if [ "$1" == "$2" ]
then
echo $3
else
echo $4
fi
}
# cross platform timeout util to support mac mostly
# https://gist.github.com/jaytaylor/6527607
function eztimeout() { perl -e 'alarm shift; exec #ARGV' "$#"; }
function testPort()
{
OPTS=""
# find out if port is open using telnet
# by saving telnet output to temporary file
# and looking for "Escape character" response
# from telnet
FILENAME="/tmp/__port_check_$(uuidgen)"
RESULT=$(eztimeout $TIMEOUT_IN_SEC telnet $HOST $PORT &> $FILENAME; cat $FILENAME | tail -n1)
rm -f $FILENAME;
SUCCESS=$(eztern "$RESULT" "Escape character is '^]'." "$VALUE_IF_OPEN" "$VALUE_IF_CLOSED")
echo "$SUCCESS"
}
testPort
My machine does not support nc or /dev/tcp/$hostname/$port but timeout, so I came back to telnet as follows:
if echo "quit" | timeout 2 telnet $SERVER $PORT 2>&1 | grep -q 'Connected to'; then
echo "Connection to $SERVER on port $PORT succeeded"
exit 0
else
echo "Connection to $SERVER on port $PORT failed"
exit 1
fi
nmap-ncat to test for local port that is not already in use
availabletobindon() {
port="$1"
nc -w 2 -i 1 localhost "$port" 2>&1 | grep -v -q 'Idle timeout expired'
return "$?"
}
I am trying to write a shell script which takes an IP address and a port number as input and outputs whether the port is open on the host.. My shell script looks like this
#!/bin/bash
name=$(echo exit | telnet $1 $2 | grep "Connected")
if [ "$name" == "" ]
then
echo "Port $2 is not open on $1"
else
echo "Port $2 is open on $1"
fi
It works fine but my output contains 2 lines, something like this:
[root#ip-172-31-8-36 Scripts]# ./test.sh 172.31.35.246 7199
Connection closed by foreign host.
Port 7199 is open on 172.31.35.246
OR
[root#ip-172-31-8-36 Scripts]# ./test.sh 172.31.35.246 7200
telnet: connect to address 172.31.35.246: Connection refused
Port 7200 is not open on 172.31.35.246
I want to suppress the 1st line from the output in both cases.
Any idea how to do it?
Direct telnet's error output to /dev/null:
name=$(echo exit | telnet $1 $2 2>/dev/null | grep "Connected")
The poor-man's nmap in pure bash:
host="127.0.0.1"
for port in {1..1024}
do
echo "" > /dev/tcp/$host/$port && echo "Port $port is open"
done 2>/dev/null
How about using netcat instead?
$ nc -v -z <host> <port>
Connection to <host> <port> port [tcp/https] succeeded!
I have a file containing multiple hosts and IPs in the format above:
alpha, 192.168.1.1
beta, 192.168.1.2
gamma, 192.168.1.3
I am trying to create a script that says something like:
"Pinging hostname alpha"
ping 192.168.1.1
and jump to the next ip in the list.
I don't want the entire script, just some suggestions.
Thanks,
Alex
If you add a comma to the input field separator, it'll help parse the lines:
IFS=$IFS,
while read name ip; do
echo -n "Pinging hostname $name..."
ping -c2 "$ip" &>/dev/null && echo success || echo fail
done < /tmp/hosts
I'd read in the lines with read. You'll probably also want to give ping an option telling it how many times to ping. The default on most Linux systems for example is to ping forever, which doesn't seem like it would work well in your situation.
You could use AWK:
$ awk '{print "Pinging hostname "$1; system("ping -c 3 "$2) }' ips
Pinging hostname alpha,
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
You can also remove that comma if is it important to you:
$ awk '{sub(/,/,"");print "Pinging hostname "$1; system("ping -c 3 "$2) }' ips
Pinging hostname alpha
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
I might be a bit late to the party, but how about fping? Use -f to read from a file (requires sudo), or pipe the file with < (as suggested on the man page). It won't tell you "pinging alpha", but it will quickly tell you whether or not you can get in touch with the hosts.
Script for hosting 100+ hosts in same scheme like 192.168.xx.xxx
#!/bin/bash
for i in `seq ${2} ${3}`
do
ping -c 1 ${1}.${i} > /dev/null 2>&1
if [ $? -eq 0 ]; then
echo "${1}.${i} responded."
else
echo "${1}.${i} did not respond."
fi
done
command to ping the host
bash test.sh 192.168.1 0 100
Try this
#!/bin/bash
IPLIST="path_to_the_Ip_list_file"
for ip in $(cat $IPLIST)
do
ping $ip -c 1 -t 1 &> /dev/null
if [ $? -ne 0 ]; then
echo $ip ping faild;
else
echo $ip ping passed;
fi
done