Parsing .ssh/config for proxy information - regex

Question

I would like to parse the .ssh/config file for proxy information contained therein and display each host that has related proxy information with the proxy information. Hosts that do not have any proxy information should be filtered out. Man page for .ssh/config: http://man-wiki.net/index.php/5:ssh_config
This should be done from a Unix shell script under Bash, so a standard tool like Perl, awk or sed is preferred.
Example input file:
Host ssh.foo.com
User ssh
HostName ssh.foo.com
Port 443
ProxyCommand /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth
Host ci
HostName 127.0.0.2
User ci
Host nightly
HostName 192.168.1.1
User goodnight
Host foobar.org
User git
HostName foobar.org
Port 443
ProxyCommand /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth
Host integration
HostName 192.168.1.2
User int
The expected output should look like this:
Host: ssh.foo.com - Proxy: /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth
Host: foobar.org - Proxy: /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth
The difficulty here is that the search has to cover multiple lines.

Answer 1

Try following awk command:
awk '
$1 == "Host" {
host = $1 ": " $2;
next;
}
$1 == "ProxyCommand" {
$1 = "";
sub( /^[[:space:]]*/, "" );
printf "%s - Proxy: %s\n", host, $0;
}
' .ssh/config
It yields:
Host: ssh.foo.com - Proxy: /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth
Host: foobar.org - Proxy: /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth

Answer 2

an awk oneliner may work for your requirement:
awk -v RS="" '/Proxy/{gsub(/\n/,"");gsub(/\s*User.*ProxyCommand/,"- Proxy:");print}'file
test (a.txt is your input file)
kent$ awk -v RS="" '/Proxy/{gsub(/\n/,"");gsub(/\s*User.*ProxyCommand/,"- Proxy:");print}' a.txt
Host ssh.foo.com - Proxy: /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth
Host foobar.org - Proxy: /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth

Answer 3

Just for kicks, here is a nasty sed command that seems to accomplish this.
sed -n '/^[Hh]ost/{:r;h;:l;n;/^[Hh]ost/!{/[Pp]roxy/H;bl};/^[Hh]ost/{x;/[Pp]roxy/{s/\n\s*/ - /;s/[Cc]ommand/:/;s/[Hh]ost/\0:/;p};x;br}}' ~/.ssh/config
This is more for demonstration purposes anyway since the other solutions are much easier to grasp. A commented view of this:
/^[Hh]ost/ { # Begin on a Host line
:restart # Label to jump back to
h # Copy the pattern space to the save space
:loop # Label to jump to when we don't want to wipe out the save space
n # Read in the next line
/^[Hh]ost/!{ # For lines that aren't host definitions
/[Pp]roxy/H # If they are proxy configurations, append the line to the save space
b loop # Go to :loop
}
/^[Hh]ost/{ # If they are *not* host definitions
x # Exchange the pattern and save spaces
/[Pp]roxy/{ # If the new pattern space contains a proxy configuration
s/\n\s*/ - / # Insert the required separator
s/[Cc]ommand/:/ # Change "ProxyCommand" to "Proxy:"
s/[Hh]ost/\0:/ # Change "Host" to "Host:"
p # Print the pattern space
}
x # Exchange the pattern and save spaces
b restart # Go to :restart
}
}
Example output:
Host: ssh.foo.com - Proxy: /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth
Host: foobar.org - Proxy: /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth

Answer 4

Have you checked out the Net::SSH::Perl::Config module ? It claims to read configs in the standard ssh format - albeit with a subset of keywords.
The configuration files should be in the same format used for the ssh
command line program; see the ssh manpage for information on this
format. Net::SSH::Perl::Config understands a subset of the
configuration directives that can live in these files; this subset
matches up with the functionality that Net::SSH::Perl can support.
Unknown keywords will simply be skipped.

Answer 5

One way using GNU sed:
sed -nre '/^Host/h;/ProxyCommand/{H;x;s/(Host)(.*)\n +[^ ]+ /\1:\2 - Proxy: /p}' file.txt
Results:
Host: ssh.foo.com - Proxy: /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth
Host: foobar.org - Proxy: /usr/local/bin/corkscrew proxy 8080 %h %p ~/.ssh/proxyauth

Answer 6

try this:
#! /usr/bin/perl
use strict;
use warnings;
open FD, "DATA" || die $!;
my $line = do {local $/; <FD>};
my #a = split /Host\b/, $line;
foreach (#a) {
if (defined $_ and /^\s*(\S+).*ProxyCommand\s+([^\n]+)/s) {
print "$1 - Proxy: $2\n";
}
}