Bash Shell Programming HowTos

Tutorials, howtos and programming tips about GNU Bourne-Again SHell (BASH) for Apple OS X, Linux, *BSD and Unix like operating systems. ( rss feed )

I‘m a new Ubuntu Linux user. In Linux, Apple OS X or Unix-like systems, how do I reissue or repeat a long command without retying it?


I have a Linux DD-WRT router DHCP server running on my network. How can I force my FreeBSD based dhcp client to get a new lease from this Linux based router? What is the command in FreeBSD equivalent to Windows’ “ipconfig /renew” command?


I‘m using CentOS 7 server. I need to run a command when I logout using ssh or bash shell. So in Linux and Unix-like systems, how can I run a command to execute when I log out my session?

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I‘m a new Linux, OS X or Unix-like system users. I’m using bash shell. I made changes to my $HOME/.profile ($HOME/.bash_profile) file. How can I restart my session without doing logout and login again?


I‘m a new Linux / Unix system user. How can I set encrypted tunnel between my desktop/laptop computer and server in a remote data center to bypass the limits in a network? How do I create a reverse SSH tunnel on Unix-like systems?


I am a new Ubuntu Linux and bash shell user. I also know how to redirect output from display/screen to a file using the following syntax:

cmd > file
ls > file

However, some time errors are displayed on screen. How do I store and redirect output from the computer screen to a file on a Linux or Unix-like systems?


I‘m a new Linux system user. I need to cleanup in a download directory i.e. delete all files from ~/Downloads/ folders except the following types:

*.iso – All iso images files.
*.zip – All zip files.

How do I delete all file except some in bash shell on a Linux, OS X or Unix-like systems?