Read hosts in ssh client configuration.

ssh-lookup.sh

#!/bin/sh

# - ssh-lookup -
#
# This script read configuration file for ssh client. Without argument it list
# all hosts entries in the file. With host as argument, it print the real address
# for this entry.
#
# $ ssh-lookup.sh
# host1.domain.tld
# host2.domain.tld
# ...
#
# compare old and new script version:
# - old script [ real 0m0.969s | user 0m1.208s | sys 0m0.468s ]
# - awk script [ real 0m0.009s | user 0m0.008s | sys 0m0.000s ]
#
# $ ssh-lookup.sh host1.domain.tld
# host1.domain.tld => www@www.domain.tld:2212
#
# or with ProxyCommand (ssh other.domain.tld nc -q 1 www.domain.tld 22):
# $ ssh-lookup.sh host2.domain.tld
# host2.domain.tld => www@www.domain.tld:2212 via other.domain.tld:22
#

if [ $# -eq 0 ]; then
	exec awk '
		BEGIN {
			count = 0
		}

		/^[Hh]ost/ {
			count += 1
			print $2
		}

		END {
			printf "\n%d item(s)\n", count
		}' $HOME/.ssh/config
else
	for host in $@; do
		awk --assign arg="$host" '
			BEGIN {
				proceed = 0
				hostname = arg
				port = 22
				user = ENVIRON["USER"]
			}

			/^[Hh]ost / {
				if (arg == $2) {
					proceed = 1
				} else {
					if (proceed == 1) {
						proceed = 0
					}
				}
			}

			/[Hh]ostname/ {
				if (proceed == 1) {
					hostname = $2
				}
			}

			/[Uu]ser/ {
				if (proceed == 1) {
					user = $2
				}
			}

			/[Pp]ort/ {
				if (proceed == 1) {
					port = $2
				}
			}

			/[Pp]roxy[Cc]ommand/ {
				if (proceed == 1) {
					phost = $3
					proxy = $7":"$8
				}
			}

			END {
				if (proxy == "") {
					print arg" => "user"@"hostname":"port
				} else {	
					print arg" => "user"@"proxy" via "phost":"port
				}
			}' $HOME/.ssh/config
	done
fi

exit 0