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Top Forums Programming Open Source Splitting files using awk and reading filename value from input data Post 302976078 by rbatte1 on Thursday 23rd of June 2016 01:35:45 PM
Old 06-23-2016
Splitting files using awk and reading filename value from input data

I have a process that requires me to read data from huge log files and find the most recent entry on a per-user basis. The number of users may fluctuate wildly month to month, so I can't code for it with names or a set number of variables to capture the data, and the files are large so I don't want to read the it several times.

The entries of interest have a particular string so I can extract just them from the overall log file and I have a way to split the output into separate files on a per-user basis, my plan being to then just read the last line of each files created with tail -1 and the filename giving me the user account in question.

My boss, however, worries about false-positive data matches for my expression (by chance or maliciously) that might try to overwrite a critical file.


My data has a syslog-type date in it which means doing a sort -u is proving tricky too. I've got this far with splitting the data out to files under /tmp/logs as splitlog.rbatte1 or similar but if field 11 were ever */../../etc/passwd then potentially I would be in trouble.

The date is the first three fields and 'as far as I am aware' a valid user name would be in field 11, but ........

A simplified part of the code would be:-
Code:
grep "Active transaction started" /var/log/qapplog | awk "{print \$1, \$2, \$3, \$11> \"/tmp/logs/splitlog.\"\$11}"
for userfile in /tmp/logs/splitlog.*
do
   lastrecord=$(tail -1 $userfile)
   printf "User %s last record is %s\n" "$userfile" "$lastrecord"
   .... whatever else here ....
done

I have considered adding tr -d "\/" to strip out the characters, but now that it's been raised, I'm concerned that there may be other things I'm not considering.

Is there a better way to work here, potentially with awk getting the equivalent of basename "$11" or variable substitution in the shell of "${{11}##*/}"?


Any suggestions welcome. Perhaps there is a better design overall that will find the last entry on a per-user basis. The log is thankfully written in time order, so the last in the file by user name is the last by time already.

Kind regards,
Robin
 

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syslog.conf(4)						     Kernel Interfaces Manual						    syslog.conf(4)

NAME
syslog.conf - syslogd configuration file SYNOPSIS
facility.severity destination Where: Is part of the system generating the message, specified in /usr/include/sys/syslog_pri.h. See also the syslogd(8) reference page. The severity level, which can be emerg, alert, crit, err, warning, notice, info, or debug. See /usr/include/sys/syslog_pri.h. The syslogd daemon logs all messages of the specified severity level plus all messages of greater severity. For example, if you specify level err, all messages of levels err, crit, alert, and emerg or panic are logged. A local file pathname to a log file, a host name for remote logging or a list of users. In the latter case the users will receive messages when they are logged in. An asterisk (*) causes a message to be sent to all users who are currently logged in. DESCRIPTION
The /etc/syslog.conf file is a system file that enables you to configure or filter events that are to be logged by syslogd. You can specify more than one facility and its severity level by separating them with semicolons. You can specify more than one facility logs to the same file by separating the facilities with commas, as shown in the EXAMPLES section. The syslogd daemon ignores blank lines and lines that begin with an octothorpe (#). You can specify # as the first character in a line to include comments in the file or to disable an entry. The facility and severity level are separated from the destination by one or more tab characters. If you want the syslogd daemon to use a configuration file other than the default, you must specify the file name with the following com- mand: # syslogd -f config_file Daily Log Files You can specify in the /etc/syslog.conf file that the syslogd daemon create daily log files. To create daily log files, use the following syntax to specify the path name of the message destination: /var/adm/syslog.dated/ { file} The file variable specifies the name of the log file, for example, mail.log or kern.log. If you specify a /var/adm/syslog.dated/file path name destination, each day the syslogd daemon creates a sub-directory under the /var/adm/syslog.dated directory and a log file in the sub-directory, using the following syntax: /var/adm/syslog.dated/ date / file Where: The date variable specifies the day, month, and time that the log file was created. The file variable specifies the name of the log file you previously specified in the /etc/syslog.conf file. The syslogd daemon automatically cre- ates a new date directory every 24 hours and also when you boot the system. The current directory is a link to the latest date directory. To get the latest logs, you only need to reference the /var/adm/syslog.dated/current directory. EXAMPLES
The following is a sample /etc/syslog.conf file: # # syslogd config file # # facilities: kern user mail daemon auth syslog lpr binary # priorities: emerg alert crit err warning notice info debug # kern.debug /var/adm/syslog.dated/kern.log user.debug /var/adm/sys- log.dated/user.log daemon.debug /var/adm/syslog.dated/daemon.log auth.crit;syslog.debug /var/adm/syslog.dated/syslog.log mail,lpr.debug /var/adm/syslog.dated/misc.log msgbuf.err /var/adm/crash.dated/msgbuf.savecore kern.debug /var/adm/messages kern.debug /dev/console *.emerg * FILES
/etc/syslog.conf /etc/syslog.auth - Authorization file for remote logging. /usr/include/sys/syslog_pri.h - Common components of a syslog event log record. RELATED INFORMATION
Commands: /usr/sbin/syslogd(8), /usr/sbin/binlogd(8) System Administration delim off syslog.conf(4)
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