.TH cyclog 1
.SH NAME
cyclog \- write a log to disk, with automatic rotation
.SH SYNOPSIS
.B cyclog
[
.B \-s\fIsize
] [
.B \-n\fInum
] [
.B \-m\fImargin
]
.I dir
.SH DESCRIPTION
.B cyclog
copies its input to a log file in the
.I dir
directory.
When that file reaches 100000 bytes,
.B cyclog
makes sure it is safely written to disk
and starts writing to a new file.
.B cyclog
also removes old files
to guarantee that there are at most 10 log files in
.IR dir .

The name of a log file is the TAI timestamp
when the file was started.
The mode of the file is 444 if it has been safely written to disk,
644 otherwise.
A log file that has not been written to disk is
not guaranteed to survive a system crash.

The
.I dir
directory must exist and be writable to
.IR cyclog .
.SH OPTIONS
.TP 5
.B \-s\fIsize
(Default: 104000. Minimum: 512.)
Maximum file size.
After writing this many bytes to one file,
.B cyclog
will start a new file.
.TP
.B \-n\fInum
(Default: 10. Minimum: 1.)
Maximum number of log files.
If
.B cyclog
sees this many files before it opens a new file,
it removes the oldest,
as determined by the starting timestamps.
.TP
.B \-m\fImargin
(Default: 4000.)
.B cyclog
tries to chop log files at line boundaries.
If it sees a newline within
.I margin
bytes of the maximum file size,
it starts a new file.
.SH "SEE ALSO"
fsync(2)