log-file-tail ( path limit -- lines omitted-bytes )

Vocabulary

logging.parser

Inputs

path	a log file path
limit	a positive byte count

Outputs

lines	a sequence of strings
omitted-bytes	the number of omitted bytes

Word description

Reads at most the last limit bytes of a log file, discarding a partial first line before decoding UTF-8. The file is closed on both success and failure.

Definition

USING: io io.encodings.binary io.encodings.string
io.encodings.utf8 io.files kernel math math.order namespaces
sequences splitting ;

IN: logging.parser

:: log-file-tail ( path limit -- lines omitted-bytes )
    limit integer? [ limit 0 > ] [ f ] if
    [ limit invalid-log-tail-limit ] unless path binary [
        input-stream get stream-length 0 or limit - 0 max
        :> start start 0 >
        [ start 1 - seek-absolute seek-input read1 10 = ] [ t ]
        if :> line-boundary? limit read B{ } or
        :> bytes line-boundary?
        [ 0 ] [ 10 bytes index [ 1 + ] [ bytes length ] if* ] if
        :> partial bytes partial tail utf8 decode
        split-lines start partial +
    ] with-file-reader ;