WHAT IS IT? =========== flog (file logger) is a program that reads input from STDIN and writes to a file. if a SIGHUP is received, the file will be reopened, allowing for log rotation [see logrotate(8) on RH.] The log file will only be reopened if flog detects that rotation has occurred (ie, old file gone or inode changed). flog is very small (less than 500 bytes memory footprint.) USAGE ===== Typically flog is used to log STDERR output from a daemon. It's also very useful with Apache. This way you never have to HUP apache itself: ErrorLog "|/bin/flog /httpd/logs/error_log" Typical example: (mydaemon >stdout.file) |& flog [-t] stderr.file this will redirect daemon's STDOUT to a file called "stdout.file" and STDERR (thru flog) to "stderr.file". (example uses zsh: the best shell! like bash but better) The -t option causes a timestamp to be prepended to each line. The -T option causes a timestamp to be prepended to each line with a user specified time format. See strftime(3) for how to specify the format. The -z option (pre-1.8 default behavior) causes the log file to be truncated to free up disk space in case the device gets full. In v1.8 the default is now to buffer additional data in ram until there is disk space available again. FEATURES ======== if flog fills up a device (write returns ENOSPC), the log file will be truncated back to 0 and restarted. (this is an emergency avoidance feature only! always use logrotate to recycle logs) send as many HUPs as you want to flog, when a HUP is caught, the LOG will only be reopened if flog detects a logrotation. (ie, inode changed, or file disappeard) CHANGE LOG ========== version 1.4 2005-01-17 Added large-file support (-D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE=1) O_LARGEFILE version 1.5 2005-02-04 Re-arm signal handler (needed for solaris. thanks Claude) version 1.6 2005-06-02 Now compiles on OpenBSD version 1.7 2005-09-01 Added -l option to limit file length (patch by dsong@teramail.com) version 1.8 2009-02-04 Added -z option, but the default is now to buffer, not to truncate log if disk gets full. AUTHOR ====== Copyright (c) 2001-2009 Fredrik Sjoholm License: GPL - The GNU General Public License