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Full Discussion: Script to count matched string then check again from last read position
Top Forums Shell Programming and Scripting Script to count matched string then check again from last read position Post 302990150 by rbatte1 on Monday 23rd of January 2017 05:37:14 AM
Old 01-23-2017
If you know the last read line number, you can use sed to get the lines past that point:-
Code:
last_seen_record=12345            # .... or whatever you have determined it to be
sed -n "$last_seen_record,$"p  $logfile

Of course, the output is then from the point you specify onward, so working out the next last_see_record value will be tricky. You might be better with:-
Code:
last_seen_record=12345            # .... or whatever you have determined it to be
grep -c "" $logfile | sed -n "$last_seen_record,$"p

This will give you output prefixed with the line number of the whole file so you can work with that to save away the appropriate value for next time.

If you have large log files, you might hit a timing problem if you try to count the number of lines read as a separate operation with wc because of the delay between counting the lines and the process that you your to read the information out.

An alternate would be to use awk to both extract the data and keep a record count in a single operation and we can explore that if you think that is more appropriate, but it can be a little harder to grasp.


Can you post the output from uname -a so we know what OS and version we're working with, because there are variations we may need to consider.



Robin
 

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LEARN ABOUT PLAN9

pcap_can_set_rfmon

PCAP_CAN_SET_RFMON(3PCAP)												 PCAP_CAN_SET_RFMON(3PCAP)

NAME

       pcap_can_set_rfmon - check whether monitor mode can be set for a not-yet-activated capture handle

SYNOPSIS

       #include <pcap/pcap.h>

       int pcap_can_set_rfmon(pcap_t *p);

DESCRIPTION

       pcap_can_set_rfmon() checks whether monitor mode could be set on a capture handle when the handle is activated.

RETURN VALUE

       pcap_can_set_rfmon()  returns  0 if monitor mode could not be set, 1 if monitor mode could be set, PCAP_ERROR_NO_SUCH_DEVICE if the capture
       source specified when the handle was created doesn't exist, PCAP_ERROR_PERM_DENIED if the process doesn't have permission to check  whether
       monitor	mode  could  be  supported,  PCAP_ERROR_ACTIVATED if called on a capture handle that has been activated, or PCAP_ERROR if an error
       occurred.  If PCAP_ERROR is returned, pcap_geterr() or pcap_perror() may be called with p as an argument to  fetch  or  display	the  error
       text.

SEE ALSO

       pcap(3PCAP), pcap_create(3PCAP), pcap_activate(3PCAP), pcap_set_rfmon(3PCAP)

								    18 May 2010 					 PCAP_CAN_SET_RFMON(3PCAP)
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