Ubuntu Manpage: multilog - reads a sequence of lines from stdin and appends selected lines to any number of logs.

Provided by: daemontools_0.76-3ubuntu3_amd64

NAME

       multilog - reads a sequence of lines from stdin and appends selected lines to any number of logs.

SYNOPSIS

       multilog script

DESCRIPTION

       script  consists  of any number of arguments. Each argument specifies one action. The actions are carried
       out in order for each line of input. Note that actions may contain shell metacharacters that need  to  be
       quoted when multilog is run from a shell.

       multilog exits 0 when it sees the end of stdin. If stdin has a partial final line then multilog inserts a
       final newline.

       multilog writes a message to stderr and exits 111, without reading any input, if it runs out of memory or
       if another multilog process is writing to one of the same automatically rotated logs.

       If  multilog  has  trouble  writing to disk after it starts reading input, it writes a message to stderr,
       pauses, and tries again, without losing any data. Note that this may block any program feeding  input  to
       multilog.

       If  multilog receives a TERM signal, it will read and process data until the next newline, and then exit,
       leaving stdin at the first byte of data it has not processed.

SELECTING LINES

       Each line is initially selected. The action

       -pattern
              deselects the line if pattern matches the line. The action

       +pattern
              selects the line if pattern matches the line.

       pattern is a string of stars and non-stars. It matches any concatenation of strings matched  by  all  the
       stars  and  non-stars  in  the  same  order.  A non-star matches itself. A star before the end of pattern
       matches any string that does not include the next character in pattern.  A star at  the  end  of  pattern
       matches any string.

       For example, the action

         +hello

       selects hello. It does not select hello world.

       The action

         -named[*]: Cleaned cache *

       deselects  named[135]: Cleaned cache of 3121 RRs. The first star matches any string that does not include
       a right bracket.

       The action

         -*

       deselects every line.

       To save memory, multilog actually checks pattern against only the first 1000 characters of each line.

ALERTS

       The action

       e      prints (the first 200 bytes of) each selected line to stderr.

STATUS FILES

       The action

       =file  replaces the contents of file with (the first 1000 bytes  of)  each  selected  line,  padded  with
              newlines to 1001 bytes. There is no protection of file against power outages.

              For example, the sequence of actions

                   -*
                   +STAT*
                   =log/status

              maintains log/status as a copy of the most recent line starting with STAT.

TIMESTAMPING

       The action

       t      inserts  an  @,  a  precise timestamp, and a space in front of each line, using the same format as
              tai64n(8).  This is required to be the first action.

       Patterns apply to the line after the timestamp is inserted. For example, if

         multilog t '-*' '+* fatal: *' ./main

       reads the line

         fatal: out of memory

       then it will log a line such as

         @400000003b4a39c23294b13c fatal: out of memory

       with the first * matching the timestamp.

       You can use tai64nlocal(8) to convert these timestamps to human-readable form.

AUTOMATICALLY ROTATED LOGS

If dir starts with a dot or slash then the action

dir appends each selected line to a log named dir. If dir does not exist, multilog creates it.

Do not attempt to write to one log from two simultaneous multilog processes, or two actions in one
process.

The log format is as follows. dir is a directory containing some number of old log files, a log
file named current, and other files for multilog to keep track of its actions. Each old log file
has a name beginning with @, continuing with a precise timestamp showing when the file was
finished, and ending with one of the following codes:

.s This file is completely processed and safely written to disk.

.u This file was being created at the moment of an outage. It may have been truncated and has not
been processed.

Beware that NFS, async filesystems, and softupdates filesystems may discard files that were not
safely written to disk before an outage.

While multilog is running, current has mode 644. If multilog sees the end of stdin, it writes
current safely to disk, and sets the mode of current to 744. When it restarts, it sets the mode of
current back to 644 and continues writing new lines.

When multilog decides that current is big enough, it writes current safely to disk, sets the mode
of current to 744, and renames current as an old log file. The action

ssize sets the maximum file size for subsequent dir actions. multilog will decide that current is big
enough if current has size bytes. (multilog will also decide that current is big enough if it
sees a newline within 2000 bytes of the maximum file size; it tries to finish log files at line
boundaries.) size must be between 4096 and 16777215. The default maximum file size is 99999.

In versions 0.75 and above: If multilog receives an ALRM signal, it immediately decides that
current is big enough, if current is nonempty. The action

nnum sets the number of log files for subsequent dir actions. After renaming current, if multilog sees
num or more old log files, it removes the old log file with the smallest timestamp. num must be
at least 2. The default number of log files is 10. The action

!processor
sets a processor for subsequent dir actions. multilog will feed current through processor and
save the output as an old log file instead of current. multilog will also save any output that
processor writes to descriptor 5, and make that output readable on descriptor 4 when it runs
processor on the next log file. For reliability, processor must exit nonzero if it has any trouble
creating its output; multilog will then run it again. Note that running processor may block any
program feeding input to multilog.