multilog - reads a sequence of lines from stdin and appends selected lines to
any number of logs.
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
is run from a shell.
exits 0 when it sees the end of stdin. If stdin has a partial
final line then multilog
inserts a final newline.
writes a message to stderr and exits 111, without reading any
input, if it runs out of memory or if another multilog
writing to one of the same automatically rotated logs.
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
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.
Each line is initially selected. The action
- deselects the line if pattern matches the line. The
- selects the line if pattern matches the line.
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
string that does not include the next character in pattern
. A star at
the end of pattern
matches any string.
For example, the action
selects hello. It does not select hello world.
-named[*]: Cleaned cache *
deselects named: Cleaned cache of 3121 RRs. The first star matches any
string that does not include a right bracket.
deselects every line.
To save memory, multilog
actually checks pattern against only the first
1000 characters of each line.
- prints (the first 200 bytes of) each selected line to
- 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
maintains log/status as a copy of the most recent line starting with
- 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
starts with a dot or slash then the action
- 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:
- This file is completely processed and safely written to
- 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
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
- 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
- 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
- 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.
supervise(8), svc(8), svok(8), svstat(8), svscanboot(8), svscan(8),
readproctitle(8), fghack(8), pgrphack(8), tai64n(8), tai64nlocal(8),
setuidgid(8), envuidgid(8), envdir(8), softlimit(8), setlock(8)