3.1. string evaluation

within the config file strings are used for all values. these value-strings will be evaluated while the config file is read. strings can optionally be delimited by double-quotes " - most of the time this is not necessary, but sometimes they help the config-parser to get things right. the evaluation will replace %()-references to defines sections with their values. example:

defines
my_name: flo
message: Hello %(my_name)

here message will evaluate to the string Hello flo.

Quoted strings can contain # characters. In unquoted single-line values, # starts a trailing line comment, so a literal hash must be quoted:

defines
literal_hash: "foo#bar"
trailing_comment: foo # this comment is ignored

these %()-references can not only refer to user-defined defines, but also to builtin-defines, builtin-functions and user-functions.

3.1.1. builtin-defines

manager: HOST_OR_IP:PORT of managers TCP-listening-socket
instance_name: name of this ln_manager instance as defined by the instance_name:-field of the instance-section described below.
hostname: hostname as reported from socket.gethostname() (host where manager runs)
CURDIR: directory-name of this config file
CURRENT: filename of this config file
_PROCESS: display-name of currently(/or last)-defined process-section
_FULL_PROCESS: full name of currently(/or last)-defined process-section
LN_LD_LIBRARY_PATH: LD_LIBRARY_PATH as used by the ln_manager itself
LN_PYTHONPATH: PYTHONPATH as used by the ln_manager itself
LN_PYTHON: filename of python executable used by the ln_manager itself
LN_PREFIX: prefix where ln_manager was installed to. (e.g. /usr/local or /usr or somewhere in your conan-cache)
LN_SHARE_DIR: share-directoy of ln_manager
LN_BASE_MANAGER: base_dir of the ln_manager itself

3.1.2. builtin-functions

Note

todo: ifeq?

env: %(env NAME[, DEFAULT_VALUE]) read value from ln_managers environment. if there is no variable of that name, return DEFAULT_VALUE if specified. if DEFAULT_VALUE is not specified a error will be generated if that variable does not exist. example: %(env "HOME") will evaluate to the contents of the HOME environment variable of the ln_manager’s environment. it will throw an error if that variable does not exist…
ifip: %(ifip IFNAME) will query the system’s network interface IFNAME and returns it’s (first) IPv4 in dottet-decimal form. (uses linux SIOCGIFADDR ioctl)
shell: %(shell CMD) executes a shell command via /bin/sh -c "CMD" and evaluates to the produced output on stdout. example: %(shell date) will evaluate to the ln_managers systems current date in some locale’s representation.
realpath: %(realpath PATH) will evaluate to the return-value of python’s os.path.realpath(PATH)
dirname: %(dirname PATH) will evaluate to the return-value of python’s os.path.dirname(PATH)
basename: %(basename PATH) will evaluate to the return-value of python’s os.path.basename(PATH)
subst: %(subst SEARCH, REPLACE, HAYSTACK) will evaluate to HAYSTACK but with all occourances of SEARCH replaced by REPLACE. example: %(substr "World", "Flo", "Hello World") will evaluate to Hello Flo.
substring: %(substring STR, START[, N]) will evaluate to the sub-string of STR, skipping the first START-characters. if N is provided only N-characters will be returned (at most). example: %(substring "Hello World", 6, 3) will evaluate to Wor.
length: %(substring STR) will evaluate to the length of STR
strip: %(strip STR) will evaluate to STR but with leading and trailing whitespace removed
findstring: %(findstring SEARCH, HAYSTACK) will evaluate to SEARCH if HAYSTACK contains SEARCH, otherwise it evaluates to the empty string. (similar to make’s $(findstring find,in))
ifndef: %(ifndef DEFINE, IF_NOT_DEFINED) will evaluate to IF_NOT_DEFINED in case DEFINE is not a known define, otherwise to the value of DEFINE:

defines
known_define: 42
message: answer is %(ifndef "known_define", "unknown")!

%(message) will evaluate to answer is 42!.

This is a string-evaluation function. It is separate from the line-level config syntax ifdef SOME_DEFINE: key: value / ifndef SOME_DEFINE: key: value described in conditional config lines: ifdef and ifndef.

ifexists: %(ifexists PATHNAME, IF_TRUE, IF_FALSE) checks if PATHNAME exists on manager’s filesystem and evaluates to either IF_TRUE or IF_FALSE. (uses the python function os.path.exists())
get_port_from_string: %(get_port_from_string ARGS...) will evaluate to a fixed port number between 1024 and 65535, depending on the value of ARGS….
get_host_ifip: %(get_host_ifip NODENAME, IFNAME) will evaluate to the ip-address of named node (can be a node-name or a host-name) and interface. example:

hosts
host1: eth0:192.168.0.1, eth1:192.168.1.1
host2: eth0:192.168.0.2, eth1:192.168.1.2

node_map
rthost: host2

defines
ip10: %(get_host_ifip "host1", "eth0")
# -> 192.168.0.1
ip21: %(get_host_ifip "rthost", "eth1")
# -> 192.168.1.2

3.1.3. runtime-variables

aside from the above %()-defines which are substituted when the config file is read, there are also some so-called runtime-variables of the form $(NAME). these are substituted only shortly before the command is executed and they can only be use in some contexts: in the command:-string of a process or within a value of an environment:-variable.

these runtime-variables exist:

$(ARCH): some string describing this hosts architecture. provided by the ln_daemon running on that host. can be configured via the arch: key in a hosts-line.
$(gui_*): some environment variable from (a possible remote) ln_manager gui. only selected env-vars are available.
$(DISPLAY) $(XAUTHORITY): values of the corresponding env-vars of the remote-gui or local manager gui. you probably want to use the forward_x11-flag instead.
$(gui_ip): ip-address of a connected remote gui.
$(manager_host): host-part of the instance-config manager: directive. This is usually empty in portable configs; you probably want to use $(LN_MANAGER) instead.
$(manager_port): listening port of the ln-manager (on the host where the manager is running). you probably want to use $(LN_MANAGER) instead.
$(LN_MANAGER): computed ip-address:port where to reach this ln_manager. this is usually automatically provided to all processes via the LN_MANAGER environment-variable.