Mac OS X Leopard - ARCAism

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CHAPTER 18 INTRODUCING DARWIN AND THE SHELL
Darwin. Of course, like all things before you are able to unleash the power of Darwin, you need
to learn a few basic commands for working with files and directories. These basics are shown
and described in Table 18-4.
Table 18-4. File and Directory Management Commands
Command Usage Description
cat cat filename The cat command lists the contents of a file. This
command was originally written to perform concatenation
functions, so if used improperly, this could have
unexpected results.
head head [-n #] filename The head command allows you to display just the
beginning of a long file using the -n option followed
by the number of lines you wish to view.
tail tail [-n #] filename The tail command allows you to display just the end of a
long file using the -n option followed by the number of
lines you wish to view.
cp cp filename filecopy cp creates copies of files.
mv mv filename newfilename mv is interesting in that it is used both to move files from
one location to another and to rename files.
rm rm filename rm permanently and immediately removes a file (or files).
mkdir mkdir newdirectory mkdir is used to create new directories.
rmdir rmdir directory rmdir is a special command used to delete directories. It’s
a safer option than rm in that it will not delete a nonempty
directory (which at times makes it more frustrating as well).
touch touch filename touch will create a new empty file. (If the file, however,
already exists, touch will merely alter the date it was last
accessed.)
CAUTION Irresponsible uses of rm can result in very bad things happening—for example, if
you happen to be utilizing root privileges (which, in general, you probably shouldn’t), and happen
to type rm -R /* at the command line, your system will immediately begin to delete itself
and everything contained within it until it deletes enough of itself that it can’t continue . . .
ever. (By the way, the -R option stands for recursive, a handy option found in many
commands.)
To illustrate how all of these work, I’ve created a test file named soliloquy4 in a directory
named Shakespeare.
First we can use the cat command to view the file:
Leopard:~/Documents/Shakespeare scott$ cat soliloquy4
Tomorrow, and tomorrow, and tomorrow,
Creeps in this petty pace from day to day
To the last syllable of recorded time,
And all our yesterdays have lighted fools
The way to dusty death. Out, out, brief candle!
Life's but a walking shadow, a poor player