Cat

2011-06-10T13:46:26Z

216.120.36.3: /* Related link */

Found in /bin/cat, when [[ca
5a8
t]] is given a file as an argument, it will print out the file contents to your console, or it can be [[redirected]] to another file or process.

samizdata# '''cat /etc/fstab'''
# Device Mountpoint FStype Options Dump Pass#
/dev/da0b none swap sw 0 0
/dev/da1b
a18
none swap sw 0 0
/dev/da0a / ufs rw 1 1
/dev/da0d /tmp ufs rw 2 2
/dev/da1e /usr ufs rw 2 2
/dev/da1d /var ufs rw 2 2
/dev/cd0 /cdrom cd9660 ro,noauto 0 0

Related commands are '''zcat''' (aka '''gzcat''') and '''bzcat''', for use with gzipped and bzipped archives, respectively. Very useful for easily reading rotated, compressed logfiles - for example, let's say I'm tracking down some jackass that keeps trying to find a way into my server, and I want to look at one of the older sections of my auth log:

ph34r# '''bzcat auth.log.0.bz2 | grep Illegal'''
Oct 19 20:47:47 ph34r sshd[35556]: Illegal user adam from 218.38.28.136
Oct 19 20:47:49 ph34r sshd[35558]: Illegal user alan from 218.38.28.136
Oct 19 20:47:52 ph34r sshd[35560]: Illegal user frank from 218.38.28.136
Oct 19 20:47:54 ph34r sshd[35562]:
5a8
Illegal user george from 218.38.28.136
Oct 19 20:47:56 ph34r sshd[35564]: Illegal user henry from 218.38.28.136
Oct 19 20:47:59 ph34r sshd[35566]: Illegal user john from 218.38.28.136
Oct 19 20:48:14 ph34r sshd[35578]: Illegal user test from 218.38.28.136

Without having to muck around with multiple steps or temporary files or any of that business, I told my server to load up the bzip archive of the last section of my auth log, decompress it, and send the results to [[grep]] so that I'd only see the entries related to "Illegal" users. And voila - I can see that the idiot at the APNIC address 218.38.28.136 is trying a [[Block repeated illegal or failed SSH logins|dictionary-style username attack]] on my server.

==Related link==
* [[Block repeated illegal or failed SSH logins]]

[[category: System Commands]]

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