Essential Unix Commands

Unix Command What it does
pwd - indicates the current working directory
cd /usr/local/chemistry - changes from current directory to "/usr/local/chemistry"
cd - changes to home directory
ls - lists files in current directory
ls -lt - lists files with time and size
ls -lt | head - lists the most recently created files

The Unix Shell

The Unix shell acts as an interface between the user and the Unix operating system. It consists of high-level (human understandable) commands that tell the Unix operating system what to do. This information in turn is transferred to the hardware (CPU) in terms of low-level (machine understandable) commands. The user brings up a "window", called a Unix shell into which high-level commands are typed.