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Logging into GMU (ORC) Computing
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You need to use GMU computers for this class
The GMU computer that you will log into is a cluster called HOPPER
Secure (ssh) software is used to login to GMU computers
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Shell Commands
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Most commands consist of the command, options or switches, and input to the command
Additional switches can be found using info or --help
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Navigating Files and Directories
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The file system is responsible for managing information on the disk.
Information is stored in files, which are stored in directories (folders).
Directories can also store other directories, which forms a directory tree.
cd path changes the current working directory.
ls path prints a listing of a specific file or directory; ls on its own lists the current working directory.
pwd prints the user’s current working directory.
/ on its own is the root directory of the whole file system.
A relative path specifies a location starting from the current location.
An absolute path specifies a location from the root of the file system.
Directory names in a path are separated with / on Unix/Linux and Mac OS, but \ on Windows.
.. means ‘the directory above the current one’; . on its own means ‘the current directory’.
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Working With Files and Directories
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cp old new copies a file.
mkdir path creates a new directory.
mv old new moves (renames) a file or directory.
rm path removes (deletes) a file.
* matches zero or more characters in a filename, so *.txt matches all files ending in .txt.
? matches any single character in a filename, so ?.txt matches a.txt but not any.txt.
Use of the Control key may be notated in many ways, including Ctrl-X, Control-X, and ^X.
The shell does not have a trash bin: once something is deleted, it’s really gone. REALLY!
Most files’ names are something.extension. The extension isn’t required, and doesn’t guarantee anything, but is normally used to indicate the type of data in the file.
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