The Unix Shell: Glossary

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 described 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.

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.

Depending on the type of work you do, you may need a more powerful text editor than Nano.

wc counts lines, words, and characters in its inputs.

cat displays the contents of its inputs.

sort sorts its inputs.

head displays the first 10 lines of its input.

tail displays the last 10 lines of its input.

command > [file] redirects a command’s output to a file (overwriting any existing content).

command >> [file] appends a command’s output to a file.

[first] | [second] is a pipeline: the output of the first command is used as the input to the second.

The best way to use the shell is to use pipes to combine simple single-purpose programs (filters).

Save commands in files (usually called shell scripts) for re-use.

bash [filename] runs the commands saved in a file.

$@ refers to all of a shell script’s command-line arguments.

$1, $2, etc., refer to the first command-line argument, the second command-line argument, etc.

Place variables in quotes if the values might have spaces in them.

Letting users decide what files to process is more flexible and more consistent with built-in Unix commands.

Unix shells can be launched in a customized way with the user’s preferences.

Aliases can be defined that substitute short strings for long or complex commands.

find finds files with specific properties that match patterns.

grep selects lines in files that match patterns.

--help is an option supported by many bash commands, and programs that can be run from within Bash, to display more information on how to use these commands or programs.

man [command] displays the manual page for a given command.

$([command]) inserts a command’s output in place.

Unix shells can be launched in a customized way with the user’s preferences.

Aliases can be defined that substitute short strings for long or complex commands.