Dan Bernstein's multilog can apparently do this - or perhaps most of it, while providing an outlet via file descriptors to !processor to make up the difference as you like - though the 20M/1G size specifications may take some finagling as it seems 16M is its outside limit per log. What follows is, in the majority, a copy+paste selection from the link above, though the link also details other options such as timestamping per line, maintaining [an]other file[s] containing only the most recent line matching pattern and more.
...script consists of any number of arguments. Each argument specifies one action. The actions are carried out in order for each line of input.
Each line is initially selected. The action...
...deselects the line if pattern matches the line. The action...
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.
Automatically rotated logs
If dir 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.
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. It has not been processed.
...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.
(Note: I suspect the
schedule builtin could be easily persuaded to send an
ALRM at specified intervals if necessary.)
...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.
...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