ssh_agent_share [OPTION]...
--help print this help message
--[no-]-inherit use/ignore SSH_AUTH_SOCK from environment
--lockwait W seconds to wait for lock (default: 1.5)
--timeout T default expiry time for all identities (3 days in secs)
--dir PATH agent credential cache path (~/.ssh/.ssh_agent_share/)
--host HOST override default hostname
Example:
eval >/dev/null "$(ssh_agent_share --lockwait 3)"
# optimized
[ -w "${SSH_AUTH_SOCK:-} ]" ||
eval >/dev/null "$(exec ssh_agent_share --lockwait 3)"
This program caches ssh-agent output (SSH_AUTH_SOCK=, SSH_AGENT_PID=) so that credentials are available across shell sessions. If --inherit is active and the environment contains a valid SSH_AUTH_SOCK, the program exits (there's nothing to configure). Otherwise, it:
- checks for a valid cache
- starts a new agent if necessary, caching the output
- sends the cached credentials to stdout (which may be
eval'd by.bashrcor other shell scripts).
Access to the cache file is protected by a lock. This avoids race conditions when starting multiple shell sessions (e.g. via tmux resurrect). The program tries to acquire the lock for --lockwait seconds, then gives up (to avoid hangs).
This program is implemented in perl. On the one hand, perl provides integrated, cross-platform flock and timeout facilities; on the other, while the interpreter startup cost is negligible, the same cannot be said about various imported modules (in particular, this is why I've eschewed using Getopt::Long and pod2usage, and why the optimized usage above doesn't call the program at all if a valid SSH_AUTH_SOCK is present).
It's possible to achieve the same functionality in .bashrc using timeout (from GNU coreutils) and flock from util-linux (or equivalents). This will reduce portability across platforms / shells, but turns out to be a bit faster (even though external executables need to be called).
Alin Mr [email protected] / MIT license.