Preloadable library to redirect syslog(3) output to stderr

Copyright (c) 2019-2020 SATOH Fumiyasu @ OSS Technology Corp., Japan
License: BSD-like (2-clause)
URL: https://GitHub.com/fumiyas/syslog-redirect
Twitter: https://twitter.com/satoh_fumiyasu

What's this?

This is a $LD_PRELOAD-able library and a wrapper script to run a command with the special syslog(3) function for redirecting syslog output to the standard error (stderr).

Use case

Run a syslog-aware service in a container environment (e.g., Docker) without a syslog daemon or the /dev/log.

How to build

Required packages: autoconf, automake, libtool, make, cc (gcc or misc)

$ sh autogen.sh
$ ./configure --prefix=/usr/local
$ make
$ sudo make install

Usage

Run a command with $LD_PRELOAD-able library:

$ LD_PRELOAD=/usr/local/lib/syslog-redirect.so syslog-aware-command
...

or:

$ /usr/local/bin/syslog-redirect --help
Usage: /usr/local/bin/syslog-redirect [OPTIONS] COMMAND [ARGUMENT ...]

Options:
 --log-level LEVEL
    Specify log level
    Default: 4 (LOG_WARNING)
 -i, --print-identity
    Print identity string to log
 -f, --print-facility
    Print facility string to log
 -l, --print-level
    Print log level string to log
 -a, --print-all
    Print identity, facility and log level string to log
$ /usr/local/bin/syslog-redirect --log-level 7 --print-all syslog-aware-command
...

Environment Variables

SYSLOG_REDIRECT_LOG_LEVEL
- Specify log level
SYSLOG_REDIRECT_PRINT_IDENTITY
- Print identity string to log if set
SYSLOG_REDIRECT_PRINT_FACILITY
- Print facility string to log if set
SYSLOG_REDIRECT_PRINT_LEVEL
- Print log level string to log if set

Note

If a target command does not call openlog(3) before syslog(3), all $SYSLOG_REDIRECT_* options do NOT function.
Some logger(1) implementations do NOT use syslog(3) function, thus syslog-redirect does not affect it.