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Full Discussion: Grep or Tail in shell script
Top Forums Shell Programming and Scripting Grep or Tail in shell script Post 302221168 by jim mcnamara on Sunday 3rd of August 2008 07:43:53 PM
Old 08-03-2008
Save a wc -l result from the logfile in a file, then use sed to resume where you left off
Code:
start=$(cat wherewasi)
now=$(sed -n '=$' logfile)
if [[ $now -lt $start]] ; then
   start=0
fi
echo $now > wherewasi
sed -n "$start, $now p" logfile | grep 'stuff i want to find'

 

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BOOTLOGD(8)						Linux System Administrator's Manual					       BOOTLOGD(8)

NAME
bootlogd - record boot messages SYNOPSIS
/sbin/bootlogd [-c] [-d] [-r] [-s] [-v] [ -l logfile ] [ -p pidfile ] DESCRIPTION
Bootlogd runs in the background and copies all strings sent to the /dev/console device to a logfile. If the logfile is not accessible, the messages will be kept in memory until it is. OPTIONS
-d Do not fork and run in the background. -c Attempt to write to the logfile even if it does not yet exist. Without this option, bootlogd will wait for the logfile to appear before attempting to write to it. This behavior prevents bootlogd from creating logfiles under mount points. -r If there is an existing logfile called logfile rename it to logfile~ unless logfile~ already exists. -s Ensure that the data is written to the file after each line by calling fdatasync(3). This will slow down a fsck(8) process running in parallel. -v Show version. -l logfile Log to this logfile. The default is /var/log/boot. -p pidfile Put process-id in this file. The default is no pidfile. BUGS
Bootlogd works by redirecting the console output from the console device. (Consequently bootlogd requires PTY support in the kernel con- figuration.) It copies that output to the real console device and to a log file. There is no standard way of ascertaining the real con- sole device if you have a new-style /dev/console device (major 5, minor 1) so bootlogd parses the kernel command line looking for con- sole=... lines and deduces the real console device from that. If that syntax is ever changed by the kernel, or a console type is used that bootlogd does not know about then bootlogd will not work. AUTHOR
Miquel van Smoorenburg, miquels@cistron.nl SEE ALSO
dmesg(8),fdatasync(3). Jul 21, 2003 BOOTLOGD(8)
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