This is a very brief introduction to some useful Unix commands, including examples of how to use each command.
pwd
| ls
| mkdir
| rmdir
|
cd
| mv
| rm
| cp
|
vi
| cat
| man
| kill
|
This command reports the current directory path. Enter the command by itself:
pwd
This command will list the files stored in a directory. To see a brief, multi-column list of the files in the current directory, enter:
ls
To also see "dot" files (configuration files that begin with a period,
such as .login
), enter:
ls -a
To see the file permissions, owners, and sizes of all files, enter:
ls -la
If the listing is long and scrolls off your screen before you can read
it, combine ls
with the less utility,
for example:
ls -la | less
This command will make a new subdirectory.
To create a subdirectory named mystuff
in the current
directory, enter:
mkdir problemas
To create a subdirectory named bohr
in the existing
directory named problemas
, enter:
mkdir problemas/bohr
Note: To make a subdirectory in a particular directory, you must have permission to write to that directory.
This command will remove a subdirectory. To remove a subdirectory
named problemas
, enter:
rmdir problemas
Note: The directory you specify for removal must be
empty. To clean it out, switch to the directory and use the
ls
and rm
commands to inspect and delete
files.
This command changes your current directory location. By default, your Unix login session begins in your home directory.
To switch to a subdirectory (of the current directory) named
problemas
, enter:
cd problemas
To switch to a directory named
problemas/bohr
, enter:
cd problemas/bohr
To move to the parent directory of the current directory, enter:
cd ..
To move to the root directory, enter:
cd /
To return to your home directory, enter:
cd
This command will move a file. You can use mv
not only
to change the directory location of a file, but also to rename files.
Unlike the cp
command, mv
will not preserve
the original file.
Note: As with the cp
command, you should
always use -i
to make sure you don't overwrite an
existing file.
To rename a file named oldname
in the current directory
to the new name newname
, enter:
mv -i oldname newname
To move a file named viejo1
from a subdirect
named
problemas/bohr
to another subdirectory named
problemas/schrodinger
(both subdirectories of the current directory), enter:
mv -i bohr/viejo1 schrodinger/.
If, in this last operation, you also wanted to give the file a new
name, such as nuevo1
, you would enter:
mv -i bohr/viejo1 schrodinger/nuevo1
This command will remove (destroy) a file. You should enter this
command with the -i
option, so that you'll be asked to
confirm each file deletion. To remove a file named junk
,
enter:
rm -i junk
Note: Using rm
will remove a file permanently, so
be sure you really want to get rid of the file before you use rm
.
This command copies a file, preserving the original and creating an
identical copy. If you already have a file with the new name,
cp
will overwrite and destroy the duplicate. For this
reason, it's safest to always add -i
after the
cp
command, to force the system to ask for your approval
before it destroys any files. The general syntax for cp
is:
cp -i oldfile newfile
To copy a file named problema1
in the directory
problemas/bohr to your current directory,
enter:
cp -i problemas/bohr/problema1 .
The .
(period) indicates the current
directory as destination, and the -i
ensures
that if there is another file named problema1
in the current
directory, you will not overwrite it by accident.
To copy a file named oldfile
in the current directory to
the new name newfile
in the problemas
subdirectory of your home directory, enter:
cp -i oldfile ~/problemas/newfile
The ~
character (tilde) is interpreted as
the path of your home directory.
Note: You must have permission to read a file in order to copy it.
This command starts the vi text editor. To edit a file named
myfile
in the current directory, enter:
vi myfile
The vi editor works fairly differently from other text editors. If you haven't used it before, you should probably look at a tutorial, such as the Knowledge Base document How do I use the vi text editor? Another helpful document for getting started with vi is A quick reference list of vi editor commands.
The very least you need to know to start using vi is that in order
to enter text, you need to switch the program from command mode to
insert mode by pressing i
. To navigate around
the document with the cursor keys, you must switch back to command
mode by pressing Esc
. To execute any of the following
commands, you must switch from command mode to ex mode by pressing
:
(the colon key): Enter
w
to save; wq
to
save and quit; q!
to quit without saving.
This command outputs the contents of a text file. You can use it to read brief files or to concatenate files together.
To append file1
onto the end of file2
,
enter:
cat file1 >> file2
To view the contents of a file named myfile
, enter:
cat myfile
Because cat
displays text without pausing, its output may quickly
scroll off your screen. Use the less command
(described below) or an editor for reading longer text files.
This command displays the manual page for a particular command. If
you are unsure how to use a command or want to find out all its
options, you might want to try using man
to view the manual
page.
For example, to learn more about the ls
command, enter:
man ls
To learn more about man
, enter:
man man
If you aren't sure of the exact command name, you can use
man
with the -k
option to help you find the
command you need. To see one line summaries of each reference page
that contains the keyword you specify, enter:
man -k keyword
Replace keyword
in the above example with the keyword
which you want to reference.
Use this command as a last resort to destroy any jobs or programs that you suspended and are unable to restart. Use the jobs command to see a list of suspended jobs. To kill suspended job number three, for example, enter:
kill %3
Now check the jobs
command again. If the job has not
been cancelled, harsher measures may be necessary. Enter:
kill -9 %3