Linux, UNIX

diff <(ls old) <(ls new) The arguments to  diff  will look like  /dev/fd/3  and  /dev/fd/4 : they are file descriptors corresponding to two pipes created by bash. When  diff  opens these files, it'll be connected to the read side of each pipe. The write side of each pipe is connected to the  ls  command. echo <(echo) <(echo)  

sysctl is an interface that allows you to make changes to a running Linux kernel. With /etc/sysctl.conf you can configure various Linux networking and system settings such as: Limit network-transmitted configuration for IPv4 Limit network-transmitted configuration for IPv6 Turn on execshield protection Prevent against the common 'syn flood attack' Turn on source IP address verification Prevents a cracker from using a spoofing attack against the IP address of the server. Logs several types of suspicious packets, such as spoofed packets, source-routed packets, and redirects.

fstab  is a configuration file that contains information of all the partitions and storage devices in your computer. The file is located under  /etc , so the full path to this file is  /etc/fstab . /etc/fstab  contains information of where your partitions and storage devices should be mounted and how. If you can't access your Windows partition from Linux, aren't able to mount your CD or write to your floppy as a normal user, or have problems with your CD-RW, you probably have a misconfigured  /etc/fstab file. So, you can usually fix your mounting problems by editing your  fstab  file.