Generate ~/.ssh/config from files in ~/.ssh/config.d

ssh_generate_config.sh

#!/bin/bash

#
# Generates SSH config from elements in config.d directory
# 2013/09/24 kristiaan.bonjean@newtec.eu
#

# Returns last modification epoch seconds for given file
# Usage: GetLastModification path
GetLastModification() {
	if [[ ! -f "$1" ]]; then
		echo "File $1 not found: defaulting last modification time to epoch 0" >&2
		echo 0
		return 0
	fi

	if [[ $(uname -a|cut -d' ' -f1) == 'Darwin' ]]; then
		# On Mac OS X
		eval $(stat -s "$1")
		echo $st_mtime
	else
		# On Linux (assuming this works)
		stat -c '%Y' "$1"
	fi
}

SSH_CONFIG=~/.ssh/config
SSH_CONFIGD=~/.ssh/config.d
M_CONFIG=$(GetLastModification $SSH_CONFIG)

[[ ! -d $SSH_CONFIGD ]] && mkdir -p $SSH_CONFIGD
LAST_M_ELEM=$(find $SSH_CONFIGD -type f|xargs ls -t|head -1)
if [[ "$LAST_M_ELEM" == "" ]]; then
	echo "No SSH config elements found: not generating SSH config file" >&2
	exit 1
fi

M_ELEM=$(GetLastModification $LAST_M_ELEM)

if [[ $M_ELEM -gt $M_CONFIG ]]; then
	# A config element was found newer than SSH config
	echo "Regenerating SSH config"
	cat <<-HEADEREND > $SSH_CONFIG
		### SSH config generated by $(basename $0) on $(date)
		### Do not modify this file directly: modify elements in ${SSH_CONFIGD} and regenerate.

	HEADEREND
	(find $SSH_CONFIGD -type f|sort|xargs cat) >> $SSH_CONFIG
fi

echo "SSH config up-to-date."