Once you open a terminal (or connect to a server via secure shell [SSH]),[2] you type in commands to interact with a program known as a shell.[10] Although GNU Bash (the Bourne Again Shell) is the most popular shell for Linux, some Linux servers and the computers in some Linux computer labs use tcsh as the default shell.[11] To learn more about which shell you're using and about how to switch to Bash if it isn't your default shell, see Section A.3.2, “Changing your shell temporarily to Bash”.
Once the shell starts up, you’ll see the shell prompt, which indicates that the shell is ready for you to type a command.
Here is the prompt that I see after I log in to Washington University Engineering's grid server: [jg18@grid ~]$
Thus, the format being used is: [username@host_machine current_directory]$
In addition, your current directory will initially be your home directory,[12] as is indicated by the tilde (~) in the prompt above.[13]
[10] The shell is covered in depth in Chapter 3, Basic shell commands and related utilities.
[11] For learning more about tcsh, Wikipedia's article might be informative. You can also learn more by typing man tcsh, using the manual (man) pages that you'll learn about in Section 2.1, “Manual (man) pages”.
[12] Like the C:\Documents and Settings\Your Username directory in Windows or the /Users/Your_Username directory in Mac OS X, your home directory in Linux stores your personal files and settings. If you're a student, your home directory is probably the top-level directory for the server disk space that your school allocates for your use.
[13] The symbol ~ is listed in Table 3.2, “Common symbols from the file system”.