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Full Discussion: BASH logging to file, limit lines
Top Forums Shell Programming and Scripting BASH logging to file, limit lines Post 303002705 by RudiC on Thursday 31st of August 2017 03:31:55 AM
Old 08-31-2017
While Don Cragun's fine proposal works brilliantly, it preserves the line count on hand, be it 8 or 800. Try piping into this (shamelessly stolen from Don Cragun) to make log.txt exactly 20 lines long, no matter what its size be:
Code:
while IFS='' read -r line
  do    tail -19 log.txt > _log.txt
        { cat _log.txt
          printf '%s\n' "$line"
        } > log.txt
  done

This User Gave Thanks to RudiC For This Post:
Don Cragun
 

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LEARN ABOUT MOJAVE

monitor

monitor(1)                                                        monitor command                                                       monitor(1)

NAME

       monitor - receive logging information from LPD

SYNOPSIS

       monitor [ -u ] [ -t ] [ port ]

DESCRIPTION

       The  monitor  program is a template for a printer status monitoring program.  It will open the specified TCP and/or UDP port, and then wait
       for accounting or other information to be sent.  It prints this information on it standard output.

OPTIONS

       -u   wait for connections on the UDP port.

       -t   wait for connections on the TCP port.

       port Use the specified port number.

EXIT STATUS

       The following exit values are returned:

       zero (0)       Successful completion.

       non-zero (!=0) An error occurred.

SEE ALSO

       lpd.conf(5), lpc(8), lpd(8), checkpc(8), lpr(1), lpq(1), lprm(1), printcap(5), lpd.conf(5), pr(1), lprng_certs(1), lprng_index_certs(1).

AUTHOR

       Patrick Powell <papowell@lprng.com>.

HISTORY

       LPRng is a enhanced printer spooler system with functionality similar to the Berkeley LPR software.  The LPRng developer  mailing  list  is
       lprng-devel@lists.sourceforge.net; subscribe by visiting https://lists.sourceforge.net/lists/listinfo/lprng-devel or sending mail to lprng-
       request@lists.sourceforge.net with the word subscribe in the body.
       The software is available via http://lprng.sourceforge.net

LPRng                                                               2006-12-09                                                          monitor(1)
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