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logwrap

logwrap.sh detects your nodejs or node binary and offers some more features that you can enable by setting these environment variables:

Space bug

As the manpage of my version of xinetd says: "There is no way to put a SPACE in an environment variable." If yours has the same problem, you can work around this with LW_ENVDEC, but only for vars that don't start with LW_ or are listed below LW_ENVDEC.

LW_DELAY

First of all, sleep a bit. Meant to slow down rapid server respawns and the resulting syslog flood. Value can be anything that your sleep command would accept, e.g. 30s.

LW_UMASK

Invoke the umask bash command early, with this argument. Defaults to 0022, i.e. let anyone read and execute newly create files/ directories/ pipes but not modify them.

LW_FUNC

Run just this one function, instead of the entire logwrap script. Meant for debugging logwrap itself.

LW_DUMPENV

Dump some debug info into this file about what the shell context looks like from inside: environment variables, paths, file descriptors, …

  • If it doesn't start with a slash, /tmp/ is prefixed.
  • If it ends with a slash, try to create a directory with that name (no-op it exists already), then append a probably-unique filename.

LW_SYSLOG_TAG

Try to redirect all output to syslog, using this tag name. Only affects output that LW_STDOUT and LW_STDERR failed to grab.

LW_STDOUT

  • . (U+002E full stop): Try to redirect stdout to stderr. (Useful to capture what would have been sent over the network.)
  • anything else: Try to redirect stdout to this file, appending to it.

LW_STDERR

Try to redirect stderr to this file, appending to it.

LW_ENVDEC

A colon-separated list of names of LV_… vars whose values shall be decoded. In this list (NOT in the actual environment), names are case-insensitive and you may omit the leading LV_.

The encoded value should be prefixed with a codec name and a colon. These codecs are supported:

  • base64: RFC 4648; also accepts base64url.
    • When using the base64 utility in your shell to encode values, double-check whether you meant to include a final newline in your input. Example: base64 <<<'hello' → aGVsbG8K → "hello\n"
  • printf: Let bash's printf render it.
  • urldecode: %hh hex decoding, using perl and a regexp.

LW_SOURCE_INIT

A colon-separated list of files that logwrap should source (meaning the so-named bash command) before it tries to use node.js.

You may want to set this to /etc/profile in order to get your usual env vars, including NODE_PATH.

  • Some versions of node ship with a profile script that discards the previous value of NODE_PATH, so with them there's no use in setting NODE_PATH via your xinetd service manifest. You can add paths via LW_NODE_PATH though.

List item magic:

  • A leading ? marks an item as optional, and the ? will be removed.
  • A leading ~/ will be replaced with the value of the the $HOME environment variable and a /.
  • If the resulting path is not a file (e.g. because it doesn't exist), logwrap will complain and fail – unless the item is optional, in which case it will be skipped silently.
  • If the source operation fails, logwrap will complain and fail, even for optional items.

LW_NODE_PATH

Will be added to your NODE_PATH environment variable. If it has been set already, old and new value are separated with a colon.

Evaluated after LW_SOURCE_INIT in order to work even when a profile script discards the old value (see above).

LW_NODEJS_CMD

What command to use to invoke node.js. Should be something like nodejs, node, or an absolute path to your node.js binary.

  • Default: Try to guess, with a fallback of node.
  • This program is used for stuff like LW_CWD_RESOLVE.

You can use newline characters to sneak arguments in.

LW_SERVER_CMD

The command to be used for the actual server invocation. Default: use LW_NODEJS_CMD

  • Special value / means to skip this part when constructing the effective command. Use this if you want to "just write your command" in the server_args setting of your xinetd service config. It's a bit like configuring server = /usr/bin/env except you can use all of the other LW_* features, like LW_STDERR=/dev/null.
  • You can use newline characters to sneak arguments in.

LW_CWD_RESOLVE

Meant to chdir into some node module's directory. If you want to chdir here, you'd set this to inetd-util-pmb/README.md, or more reliably, inetd-util-pmb/package.json.

Takes a colon-separated list of node module identifiers. They're each require.resolve()d with node, stopping at the first success. (If none of them resolve, fatal error.) If the resolved path has any slashes in it, cut at the last slash. Try to chdir into whatever remains.

LW_CWD

Try to chdir into whatever this variable's value is. This happens after LW_CWD_RESOLVE so you can refine its result.

LW_SOURCE_LATE

Like LW_SOURCE_INIT but it happens later, especially after the chdirs, which may give you better opportunities for some relative paths.

LW_REQUIRE

Takes a colon-separated list of node module identifiers. Each of them is given to nodejs via the -r option.

LW_EVAL

Given to nodejs via the -e option.

LW_PVAL

Given to nodejs via the -p option.

LW_SCRIPT

Path to your node script, if you want to run one.

Added to the nodejs command after all the potential -r/-e/-p options. Also, -- is added after the script path.

LW_BASH_REPL

Start a bash(!) REPL (read-eval-print loop) just before nodejs would be started.

If you have redirected output (normal and/or errors), remember to watch the destination in addition to your input channel.

The value is expected to be a file system path to an acceptable REPL input, i.e. something that forgets those bytes that have been read from it, like a named pipe or a character device or a socket. If it's neither, tries to create a named pipe with that name.

  • - is an alias for /dev/stdin. This will only work for services with wait=no, as you'd need a client socket on stdin.

As long as it's (still) an acceptable REPL input, the REPL reads one line from it, then evals it, unless it's one of these magic commands:

  • pid: Show the REPL's process ID.
  • unrepl or Q: Quit the REPL cleanly, to continue normal operation.
  • rmrepl or Qr: Like Q but try to delete the input pipe.
  • flinch or panic or DIE: Alias for exit 42.

If you delete the input while the REPL is still active, it will remind you to clean up, then fail, which should make logwrap flinch.

LW_FAIL_BASH

In case your main nodejs command failed, eval this in bash. Magic values:

  • REPL: + optional path: Do the REPL stuff as described for LW_BASH_REPL. Empty path means to use LW_BASH_REPL; if that's empty as well, do nothing.

LW_FAIL_WAIT

In case your main nodejs command failed, take a nap, like LW_DELAY.