Added improved ssh-agent support.

.bash_logout

@@ -1,4 +1,7 @@
-if (( $SHLVL == 1 )); then
+#!/bin/bash - not strictly necessary, but helps nano with syntax highlighting.
+
+# Clear the screen/console on logout.
+if (( $SHLVL == 10 )); then
   if [ -x /usr/bin/clear_console ]; then
     /usr/bin/clear_console -q
   elif [ -x /usr/bin/clear ]; then
@@ -9,3 +12,25 @@ if (( $SHLVL == 1 )); then
     echo -ne "\E[2J"
   fi
 fi
+
+# Remove the SSH_AUTH_SOCK from the agents file.
+(( $SHLVL == 1 )) && {
+  hash ssh-add ssh-agent >/dev/null 2>&1 && [[ ! -z "$SSH_AGENT_PID" ]] && [[ ! -z "$SSH_AUTH_SOCK" ]] && {
+    exec 9>~/.ssh/agents.lock
+    if flock -E 10 -w 0.5 9; then
+      _pop_agent_sock || {
+        echo -e "$(tput setaf 1 || tput AF 1)Failed to clean up agents file!$(tput op)"
+        _SLEEP=3
+      }
+    else
+      echo "$(tput setaf 1 || tput AF 1)Failed to obtain lockfile!$(tput op)"
+      _SLEEP=3
+    fi
+    exec 9>&-
+    ssh-agent -k >/dev/null 2>&1 || {
+      echo -e "$(tput setaf 1 || tput AF 1)Failed to kill ssh-agent!$(tput op)"
+      _SLEEP=3
+    }
+    sleep ${_SLEEP:-0}
+  }
+}

.bash_profile

@@ -35,43 +35,62 @@ unset _PLATFORM
 [ -d "$HOME/.local/bin" ] && export PATH="$HOME/.local/bin:$PATH"
 [ -d "$HOME/bin" ] && export PATH="$HOME/bin:$PATH"
 
-# SSH agent.
+# Make ssh-agent work better.
 hash ssh-add ssh-agent >/dev/null 2>&1 && {
-  if [ ! -z "$SSH_AUTH_SOCK" ]; then
+  if [[ -z "$SSH_AUTH_SOCK" ]]; then
-    ssh-add -l >/dev/null 2>&1
+    # Try to find an existing agent socket to connect to.
-    if (( $? < 2 )); then
+    SSH_AUTH_SOCK="$(_find_agent_sock)"
+    if ((${PIPESTATUS[0]} == 0)); then
+      # Found a socket.
+      export SSH_AUTH_SOCK
       echo "Connected to ssh-agent."
-      echo
       alias ssh='ssh-add -l >/dev/null 2>&1 && unalias ssh || { ssh-add && unalias ssh; }; ssh'
     else
-      echo -e '$(tput setaf 1 || tput AF 1)Problem connecting to forwarded ssh-agent!$(tput op)'
+      # No viable socket - try to start an agent.
-      echo
+      eval "$(ssh-agent -s | grep -v 'echo')"
-    fi
+      ssh-add -l >/dev/null 2>&1
-  else
+      if (( $? < 2 )); then
-    . ~/.ssh/agent 2>/dev/null
+        # Agent started - add new socket to the agent sockets file.
-    ssh-add -l >/dev/null 2>&1
+        exec 9>~/.ssh/agents.lock
-    if (( $? < 2 )); then
+        if flock -E 10 -w 0.5 9; then
-      echo "Connected to ssh-agent."
+          if _push_agent_sock; then
-      echo
+            echo "Started new ssh-agent."
-      alias ssh='ssh-add -l >/dev/null 2>&1 && unalias ssh || { ssh-add && unalias ssh; }; ssh'
+          else
-    else
+            echo "$(tput setaf 1 || tput AF 1)Started new ssh-agent, but failed to register socket!$(tput op)"
-      if ssh-agent -s | sed -e '/^echo/ d' >~/.ssh/agent; then
+          fi
-        . ~/.ssh/agent
-        ssh-add -l >/dev/null 2>&1
-        if (( $? < 2 )); then
-          echo "Started new ssh-agent."
-          echo
-          alias ssh='ssh-add -l >/dev/null 2>&1 && unalias ssh || { ssh-add && unalias ssh; }; ssh'
         else
-          echo "$(tput setaf 1 || tput AF 1)Problem connecting to local ssh-agent!$(tput op)"
+          echo "$(tput setaf 1 || tput AF 1)Failed to obtain lockfile!$(tput op)"
-          echo
         fi
+        exec 9>&-
+        alias ssh='ssh-add -l >/dev/null 2>&1 && unalias ssh || { ssh-add && unalias ssh; }; ssh'
       else
-        echo "$(tput setaf 1 || tput AF 1)Failed to start local ssh-agent!$(tput op)"
+        echo "$(tput setaf 1 || tput AF 1)Failed to start new ssh-agent!$(tput op)"
-        echo
+        unset SSH_AGENT_PID SSH_AUTH_SOCK
       fi
     fi
+  else
+    # Got a forwarded ssh-agent connection.
+    export SSH_AUTH_SOCK
+    ssh-add -l >/dev/null 2>&1
+    if (( $? < 2 )); then
+      # Agent is connected - add new socket to the agent sockets file.
+      exec 9>~/.ssh/agents.lock
+      if flock -E 10 -w 0.5 9; then
+        if _push_agent_sock; then
+          echo "Connected to forwarded ssh-agent."
+        else
+          echo -e "$(tput setaf 1 || tput AF 1)Failed to register forwarded ssh-agent socket!$(tput op)"
+        fi
+      else
+        echo "$(tput setaf 1 || tput AF 1)Failed to obtain lockfile!$(tput op)"
+      fi
+      exec 9>&-
+      alias ssh='ssh-add -l >/dev/null 2>&1 && unalias ssh || { ssh-add && unalias ssh; }; ssh'
+    else
+      echo -e "$(tput setaf 1 || tput AF 1)Problem connecting to forwarded ssh-agent!$(tput op)"
+    fi
   fi
+  echo
 }
 
 # Screen.

.bashrc

@@ -1,3 +1,105 @@
+# Functions.
+_agent_prompt_command() {
+  hash ssh-add >/dev/null 2>&1 && {
+    local SOCK
+    declare -g _SSH_PROMPT_ERROR_ISSUED
+    # Check the ssh agent socket is still alive.
+    ssh-add -l >/dev/null 2>&1
+    if (($? >= 2)); then
+      # Auth socket has become unusable, search for a new one.
+      SOCK="$(_find_agent_sock)"
+      if ((${PIPESTATUS[0]} == 0)); then
+        export SSH_AUTH_SOCK="$SOCK"
+        _SSH_PROMPT_ERROR_ISSUED=0
+        echo "Connected to alternate ssh-agent - you may need to re-add keys."
+      else
+        if [[ -z "$(egrep -v '^$' ~/.ssh/agents)" ]]; then
+          ((${_SSH_PROMPT_ERROR_ISSUED:-0} == 0)) && {
+            echo "$(tput setaf 1 || tput AF 1)Lost connection to ssh-agent - no alternate available!$(tput op)"
+            unset SSH_AUTH_SOCK
+            _SSH_PROMPT_ERROR_ISSUED=1
+          }
+        else
+          ((${_SSH_PROMPT_ERROR_ISSUED:-0} == 0)) && {
+            echo "$(tput setaf 1 || tput AF 1)Lost connection to ssh-agent - failed to connect to new agent!$(tput op)"
+            unset SSH_AUTH_SOCK
+            _SSH_PROMPT_ERROR_ISSUED=1
+          }
+        fi
+      fi
+    else
+      _SSH_PROMPT_ERROR_ISSUED=0
+    fi
+    unset SOCK
+  }
+}
+
+_clean_agent_socks() {
+  local I SSH_AUTH_SOCK
+  # Go through the array of sockets and validate each one.
+  for ((I = 0; I < ${#SOCKS[@]}; I++)); do
+    SSH_AUTH_SOCK="${SOCKS[$I]}" ssh-add -l >/dev/null 2>&1
+    (($? >= 2)) && {
+      unset SOCKS[$I]
+    }
+  done
+}
+
+_find_agent_sock() {
+  local I IFS=$'\n' REPLY SOCKS=() SSH_AUTH_SOCK="$SSH_AUTH_SOCK"
+  # Load the array of sockets, minus the one we know is unusable.
+  if ((${BASH_VERSINFO[0]} >= 4)); then
+    mapfile -t SOCKS < <(egrep -v "^$SSH_AUTH_SOCK\$" ~/.ssh/agents 2>/dev/null)
+  else
+    while read -r; do
+      SOCKS+=("$REPLY")
+    done < <(egrep -v "^$SSH_AUTH_SOCK\$" ~/.ssh/agents 2>/dev/null)
+  fi
+  # Search backwards through the list to find an active socket.
+  for ((I = (${#SOCKS[@]} - 1); I >= 0; I--)); do
+    SSH_AUTH_SOCK="${SOCKS[$I]}" ssh-add -l >/dev/null 2>&1
+    (($? <= 1)) && [[ ! -z "${SOCKS[$I]}" ]] && {
+      printf "%s" "${SOCKS[$I]}"
+      return 0
+    }
+  done
+  return 1
+}
+
+_pop_agent_sock() {
+  local IFS=$'\n' REPLY SOCKS=()
+  # Read the current list of auth sockets.
+  if ((${BASH_VERSINFO[0]} >= 4)); then
+    mapfile -t SOCKS < <(egrep -v "^$SSH_AUTH_SOCK\$" ~/.ssh/agents 2>/dev/null)
+  else
+    while read -r; do
+      SOCKS+=("$REPLY")
+    done < <(egrep -v "^$SSH_AUTH_SOCK\$" ~/.ssh/agents 2>/dev/null)
+  fi
+  # Clean up any dead sockets - this modifies the SOCKS array.
+  _clean_agent_socks
+  # Write the new list back to disk.
+  printf "%s\n" "${SOCKS[@]}" >~/.ssh/agents
+  return $?
+}
+
+_push_agent_sock() {
+  local IFS=$'\n' REPLY SOCKS=()
+  # Read the current list of auth sockets.
+  if ((${BASH_VERSINFO[0]} >= 4)); then
+    mapfile -t SOCKS <~/.ssh/agents
+  else
+    while read -r; do
+      SOCKS+=("$REPLY")
+    done <~/.ssh/agents
+  fi
+  # Clean up any dead sockets - this modifies the SOCKS array.
+  _clean_agent_socks
+  # Write the new list back to disk.
+  printf "%s\n" "${SOCKS[@]}" "$SSH_AUTH_SOCK" >~/.ssh/agents
+  return $?
+}
+
 # Make bash a little more pleasent - these are valid for all versions.
 shopt -s cdspell checkhash checkwinsize cmdhist histappend no_empty_cmd_completion