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

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,
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ROTATELOGS(8)							    rotatelogs							     ROTATELOGS(8)

rotatelogs - Piped logging program to rotate Apache logs SYNOPSIS
rotatelogs [ -l ] [ -L linkname ] [ -p program ] [ -f ] [ -v ] [ -e ] [ -c ] [ -n number-of-files ] logfile rotationtime|filesize(B|K|M|G) [ offset ] SUMMARY
rotatelogs is a simple program for use in conjunction with Apache's piped logfile feature. It supports rotation based on a time interval or maximum size of the log. OPTIONS
-l Causes the use of local time rather than GMT as the base for the interval or for strftime(3) formatting with size-based rotation. -L linkname Causes a hard link to be made from the current logfile to the specified link name. This can be used to watch the log continuously across rotations using a command like tail -F linkname. -p program If given, rotatelogs will execute the specified program every time a new log file is opened. The filename of the newly opened file is passed as the first argument to the program. If executing after a rotation, the old log file is passed as the second argument. rotatelogs does not wait for the specified program to terminate before continuing to operate, and will not log any error code returned on termination. The spawned program uses the same stdin, stdout, and stderr as rotatelogs itself, and also inherits the environment. -f Causes the logfile to be opened immediately, as soon as rotatelogs starts, instead of waiting for the first logfile entry to be read (for non-busy sites, there may be a substantial delay between when the server is started and when the first request is handled, meaning that the associated logfile does not "exist" until then, which causes problems from some automated logging tools) -t Causes the logfile to be truncated instead of rotated. This is useful when a log is processed in real time by a command like tail, and there is no need for archived data. No suffix will be added to the filename, however format strings containing '%' characters will be respected. -v Produce verbose output on STDERR. The output contains the result of the configuration parsing, and all file open and close actions. -e Echo logs through to stdout. Useful when logs need to be further processed in real time by a further tool in the chain. -c Create log file for each interval, even if empty. -n number-of-files Use a circular list of filenames without timestamps. With -n 3, the series of log files opened would be "logfile", "logfile.1", "logfile.2", then overwriting "logfile". logfile rotationtime The time between log file rotations in seconds. The rotation occurs at the beginning of this interval. For example, if the rotation time is 3600, the log file will be rotated at the beginning of every hour; if the rotation time is 86400, the log file will be rotated every night at midnight. (If no data is logged during an interval, no file will be created.) filesize(B|K|M|G) The maximum file size in followed by exactly one of the letters B (Bytes), K (KBytes), M (MBytes) or G (GBytes). .PP When time and size are specified, the size must be given after the time. Rotation will occur whenever either time or size limits are reached. offset The number of minutes offset from UTC. If omitted, zero is assumed and UTC is used. For example, to use local time in the zone UTC -5 hours, specify a value of -300 for this argument. In most cases, -l should be used instead of specifying an offset. EXAMPLES
CustomLog "|bin/rotatelogs /var/logs/logfile 86400" common This creates the files /var/logs/logfile.nnnn where nnnn is the system time at which the log nominally starts (this time will always be a multiple of the rotation time, so you can synchronize cron scripts with it). At the end of each rotation time (here after 24 hours) a new log is started. CustomLog "|bin/rotatelogs -l /var/logs/logfile.%Y.%m.%d 86400" common This creates the files /var/logs/ where yyyy is the year, mm is the month, and dd is the day of the month. Logging will switch to a new file every day at midnight, local time. CustomLog "|bin/rotatelogs /var/logs/logfile 5M" common This configuration will rotate the logfile whenever it reaches a size of 5 megabytes. ErrorLog "|bin/rotatelogs /var/logs/errorlog.%Y-%m-%d-%H_%M_%S 5M" This configuration will rotate the error logfile whenever it reaches a size of 5 megabytes, and the suffix to the logfile name will be cre- ated of the form errorlog.YYYY-mm-dd-HH_MM_SS. CustomLog "|bin/rotatelogs -t /var/logs/logfile 86400" common This creates the file /var/logs/logfile, truncating the file at startup and then truncating the file once per day. It is expected in this scenario that a separate process (such as tail) would process the file in real time. PORTABILITY
The following logfile format string substitutions should be supported by all strftime(3) implementations, see the strftime(3) man page for library-specific extensions. o %A - full weekday name (localized) o %a - 3-character weekday name (localized) o %B - full month name (localized) o %b - 3-character month name (localized) o %c - date and time (localized) o %d - 2-digit day of month o %H - 2-digit hour (24 hour clock) o %I - 2-digit hour (12 hour clock) o %j - 3-digit day of year o %M - 2-digit minute o %m - 2-digit month o %p - am/pm of 12 hour clock (localized) o %S - 2-digit second o %U - 2-digit week of year (Sunday first day of week) o %W - 2-digit week of year (Monday first day of week) o %w - 1-digit weekday (Sunday first day of week) o %X - time (localized) o %x - date (localized) o %Y - 4-digit year o %y - 2-digit year o %Z - time zone name o %% - literal `%' Apache HTTP Server 2013-06-13 ROTATELOGS(8)

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