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Full Discussion: Shell script to read multiple options from file, line by line
Top Forums Shell Programming and Scripting Shell script to read multiple options from file, line by line Post 302653625 by haggismn on Saturday 9th of June 2012 03:45:09 PM
Old 06-09-2012
Shell script to read multiple options from file, line by line
Hi all
I have spent half a day trying to create a shell script which reads a configuration file on a line by line basis.

The idea of the file is that each will contain server information, such as IP address and various port numbers. The line could also be blank (The file is user created). Here is an example

Code:
$ cat /tmp/servers
172.18.1.1

172.18.50.1 tcp SSH SSL=8443

The script should ignore any empty lines, obviously. For the line with server 172.18.1.1, default settings should be used as nothing else is specified (Default is UDP mode port 500). For the line 172.18.50.1, the specified settings are that tcp mode is to be used, and SSH and SSL on port 8443 options are also to be used.

This is what I have created, as an example. The final product will obviously do much more, it is the reading in of the lines and variables that I need help with.

Code:
#!/bin/sh
cat /tmp/servers | while read SRV ; do
IP=$(grep -o '^[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}' $SRV)
if [ ! -z $IP ] ; then
if grep -i "tcp" $SRV ; then TCP=1 ; fi
if grep -i "udp" $SRV ; then UDP=1 ; fi
if ! grep -i "tcp" $SRV ; then UDP=1 ; fi
SSL=$(grep -i -o 'ssl=[0-9]\{1,5\}' $SRV | cut -d = -f2) ; if [ -z $SSL] ; then if grep -i "ssl" $SRV ; then SSL=443 ; fi ; fi
SSH=$(grep -i -o 'ssh=[0-9]\{1,5\}' $SRV | cut -d = -f2) ; if [ -z $SSH] ; then if grep -i "ssh" $SRV ; then SSH=22 ; fi ; fi
HTTP=$(grep -i -o 'http=[0-9]\{1,5\}' $SRV | cut -d = -f2) ; if [ -z $HTTP] ; then if grep -i "http" $SRV ; then HTTP=80 ; fi ; fi 
echo "$IP $SSL $SSH $HTTP" 
fi ; done

The idea here is that each line will be read in. grep will attempt to find a valid IP address in that line, and if it does ( if [ ! -z $IP ] ) then the line will be checked for all possible options. Otherwise if there is no valid IP address on the line it will go to the next line.

I know that I am going wrong somewhere. I cannot use the $SRV string to get any information, although this pasted script simply gives no response. I also believe that using
Code:
if [ ! -z $SRV ]

will not work with the servers file where the line contains spaces. Is this true?

Can anyone advise on the commands I should be using to read the lines and gain these variables. Could I use a for loop instead?

Thanks for any help

PS also, is the usage of grep ok? I had used awk before but this seems to work ok and be shorter. Is there any advantage of one over the other? Thanks
Last edited by haggismn; 06-09-2012 at 06:05 PM.. Reason: fixed ssl,ssh,http if -z statements
 

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LEARN ABOUT DEBIAN

sslh

SSLH(1p)						User Contributed Perl Documentation						  SSLH(1p)

NAME

       sslh - Switch incoming connection between SSH and SSL/HTTPS servers

SYNOPSIS

       sslh [ -v ] [ -p [host:]port ] [ -t timeout ]
	    [ --ssh [host:]port ] [ --ssl [host:]port ]

DESCRIPTION

       sslh is a simple script that lets you switch an incoming connection on a single port between distinct SSH and SSL/HTTPS servers.

       sslh listens for connections on a port and is able to redirect them either to an HTTPS web server or a SSH server.

       This lets one setup both a HTTPS web server and a SSH server and access them through the same host+port.

OPTIONS

       The program follows the usual GNU command line syntax, with long options starting with two dashes.

       -p, --port [host:]port
	   The port the proxy will listen to.  If no port is given, 443 is used by default.  If no host is given, "localhost" is used by default.

       -s, --ssh [host:]port
	   The SSH server which the SSH connections must be forwarded to.  If omitted, the default is localhost:22.

       -l, --ssl, --https [host:]port
	   The HTTPS server which the HTTPS connections must be forwarded to.  If omitted, the default is localhost:443.

       -t, --timeout delay
	   Timeout in seconds before a silent incoming connection is considered as a SSH connection. The number can be fractional.

	   The default is 2seconds.

       -v, --verbose
	   Verbose output.  This option can be used several times for more verbose output.

EXAMPLE OF USE

       Is this tool actually useful? Yes.

       For example one can use it to access both a SSH server and a secure web server via a corporate proxy that only accepts to relay connections
       to port 443. Creating a tunnel that passes SSH connection through a CONNECT-enabled web proxy is easy with connect-tunnel (also included in
       the "Net::Proxy" distribution).

       The proxy will let both SSH and HTTPS connections out (since they all point to port 443), and the home server will connect those incoming
       connections to the appropriate server. This only requires to run the HTTPS server on a non standard port (not 443).

TECHNICAL NOTE

       How can this proxy find out what kind of protocol is using a TCP connection to port 443, without being connected (yet) to the server?  We
       actually rely on a slight difference between the SSL and SSH protocols (found thanks to ethereal):

       SSH Once the TCP connection is established, the server speaks first, presenting itself by saying something like:

	       SSH-2.0-OpenSSH_3.6.1p2 Debian 1:3.6.1p2-1

       SSL With SSL, it's always the client that speaks first.

       This means that sslh can be used with any pair of protocols/services that share this property (the client speaks first for one and the
       server speaks first for the other).

AUTHORS

       Original idea and C version
	   Frederic Ple "<sslh@wattoo.org>".

       Perl versions
	   Philippe 'BooK' Bruhat "<book@cpan.org>".

SCRIPT HISTORY

       Version 0.01 of the script was a quick hack designed in 2003 as a proof of concept.

       Version 0.02 (and higher) are based on "Net::Proxy", and included with the "Net::Proxy" distribution. Version 0.02 didn't work, though.

       Version 0.03 correctly initialised the "in" connector.

       Version 0.04 lets the proxy listen on any address (instead of "localhost", which is still the default). Thanks to Dieter Voegtli for
       spotting this.

SEE ALSO

       Net::Proxy, Net::Proxy::Connector::dual.

COPYRIGHT

       Copyright 2003-2006, Philippe Bruhat. All rights reserved.

LICENSE

       This module is free software; you can redistribute it or modify it under the same terms as Perl itself.

perl v5.10.1							    2009-10-18								  SSLH(1p)
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