Count the total time spent on a given command

Use TFTP protocol to transfer files between the local machine and tftp server

Execute conditional expression.

Name temporary files in shell

Log in to the remote host and management (test whether the ip port is connected)

Switch the run level of the currently running system

Reads data from standard input and redirects to standard output and files.

Resend the package saved in PCAP file for performance or functional testing

A sniffer tool, a packet capture tool and sniffer on Linux

Save many files together to a single tape or disk archive and restore the required files individually from the archive.

Let users chat with other users

Displays the last few lines of the specified file on the screen, usually used for trace output of log files.