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See the Unix
tutorial
for a leisurely, self-paced introduction on how to use the
commands listed below. For more documentation on a command,
consult a good book, or use the man pages. For example, for
more information on
grep, use the command
man grep.
Contents
-
cat
--- for creating and displaying short files
-
chmod
--- change permissions
-
cd
--- change directory
-
cp
--- for copying files
-
date
--- display date
-
echo
--- echo argument
-
ftp
--- connect to a remote machine
to download or upload files
-
grep
--- search file
-
head
--- display first part of file
-
ls
--- see what files you have
-
lpr
--- standard print command (see also
print
)
-
more
--- use to read files
-
mkdir
--- create directory
-
mv
--- for moving and renaming files
-
ncftp
--- especially good for downloading
files via anonymous ftp.
-
print
--- custom print command (see also
lpr
)
-
pwd
--- find out what directory you are in
-
rm
--- remove a file
-
rmdir
--- remove directory
-
rsh
--- remote shell
-
setenv
--- set an environment variable
-
sort
--- sort file
- tail
--- display last part of file
- tar --- create an archive, add or extract files
-
telnet
--- log in to another machine
-
wc
--- count characters, words, lines
cat
This is one of the most flexible Unix commands. We can use
to create, view and concatenate files. For our first
example we create a three-item English-Spanish dictionary
in a file called "dict."
% cat >dict
red rojo
green verde
blue azul
<control-D>
%
<control-D> stands for "hold the control key
down, then tap 'd'". The symbol
> tells
the computer that what is typed is to be put
into
the file
dict.
To view a file we use
cat in a different way:
% cat dict
red rojo
green verde
blue azul
%
If we wish to add text to an existing file we do this:
% cat >>dict
white blanco
black negro
<control-D>
%
Now suppose that we have another file
tmp that
looks like this:
% cat tmp
cat gato
dog perro
%
Then we can join
dict and
tmp like this:
% cat dict tmp >dict2
We could check the number of lines in the new file like
this:
% wc -l dict2
8
The command
wc
counts things --- the number of characters, words, and line
in a file.
chmod
This command is used to change the permissions of a file or
directory. For example to make a file
essay.001
readable by everyone, we do this:
% chmod a+r essay.001
To make a file, e.g., a shell script
mycommand
executable, we do this
% chmod +x mycommand
Now we can run
mycommand as a command.
To check the permissions of a file, use
ls -l
. For more information on
chmod, use
man chmod.
cd
Use
cd to change directory. Use
pwd
to see what directory you are in.
% cd english
% pwd
% /u/ma/jeremy/english
% ls
novel poems
% cd novel
% pwd
% /u/ma/jeremy/english/novel
% ls
ch1 ch2 ch3 journal scrapbook
% cd ..
% pwd
% /u/ma/jeremy/english
% cd poems
% cd
% /u/ma/jeremy
Jeremy began in his home directory, then went to his english
subdirectory. He listed this directory using
ls
, found that it contained two entries, both of which happen
to be diretories. He cd'd to the diretory
novel,
and found that he had gotten only as far as chapter 3 in his
writing. Then he used
cd .. to jump back one level.
If had wanted to jump back one level, then go to
poems
he could have said
cd ../poems. Finally he
used
cd with no argument to jump back to his home
directory.
cp
Use
cp to copy files or directories.
% cp foo foo.2
This makes a copy of the file foo.
% cp ~/poems/jabber .
This copies the file jabber in the directory poems to the
current directory. The symbol "." stands for the
current directory. The symbol "~" stands for the
home directory.
date
Use this command to check the date and time.
% date
Fri Jan 6 08:52:42 MST 1995
echo
The
echo command echoes its arguments. Here are
some examples:
% echo this
this
% echo $EDITOR
/usr/local/bin/emacs
% echo $PRINTER
b129lab1
Things like
PRINTER are so-called
environment
variables. This one stores the name of the default
printer --- the one that print jobs will go to unless you
take some action to change things. The dollar sign before
an environment variable is needed to get the value in the
variable. Try the following to verify this:
% echo PRINTER
PRINTER
ftp
Use
ftp to connect to a remote machine,
then upload or download files. See also:
ncftp
Example 1: We'll connect to
the machine
fubar.net, then change
director to
mystuff, then download
the file
homework11:
% ftp solitude
Connected to fubar.net.
220 fubar.net FTP server (Version wu-2.4(11) Mon Apr 18 17:26:33 MDT 1994) ready.
Name (solitude:carlson): jeremy
331 Password required for jeremy.
Password:
230 User jeremy logged in.
ftp> cd mystuff
250 CWD command successful.
ftp> get homework11
ftp> quit
Example 2: We'll connect to
the machine
fubar.net, then change
director to
mystuff, then upload
the file
collected-letters:
% ftp solitude
Connected to fubar.net.
220 fubar.net FTP server (Version wu-2.4(11) Mon Apr 18 17:26:33 MDT 1994) ready.
Name (solitude:carlson): jeremy
331 Password required for jeremy.
Password:
230 User jeremy logged in.
ftp> cd mystuff
250 CWD command successful.
ftp> put collected-letters
ftp> quit
The ftp program sends files in ascii (text) format
unless you specify binary mode:
ftp> binary
ftp> put foo
ftp> ascii
ftp> get bar
The file
foo was transferred in binary mode,
the file
bar was transferred in ascii mode.
grep
Use this command to search for information in a file or
files. For example, suppose that we have a file
dict
whose contents are
red rojo
green verde
blue azul
white blanco
black negro
Then we can look up items in our file like this;
% grep red dict
red rojo
% grep blanco dict
white blanco
% grep brown dict
%
Notice that no output was returned by
grep brown.
This is because "brown" is not in our dictionary
file.
Grep can also be combined with other commands. For example,
if one had a file of phone numbers named "ph", one entry per line,
then the following command would give an alphabetical list
of all persons whose name contains the string "Fred".
% grep Fred ph | sort
Alpha, Fred: 333-6565
Beta, Freddie: 656-0099
Frederickson, Molly: 444-0981
Gamma, Fred-George: 111-7676
Zeta, Frederick: 431-0987
The symbol "|" is called "pipe." It pipes the output
of the grep command into the input of the sort command.
For more information on
grep, consult
% man grep
head
Use this command to look at the head of a file. For
example,
% head essay.001
displays the first 10 lines of the file
essay.001
To see a specific number of lines, do this:
% head -n 20 essay.001
This displays the first 20 lines of the file.
ls
Use
ls to see what files you have. Your files are
kept in something called a directory.
% ls
foo letter2
foobar letter3
letter1 maple-assignment1
%
Note that you have six files. There are some useful
variants of the
ls command:
% ls l*
letter1 letter2 letter3
%
Note what happened: all the files whose name begins with
"l" are listed. The asterisk (*) is the "
wildcard" character. It matches any string.
lpr
This is the standard Unix command for printing a file. It
stands for the ancient "line printer." See
% man lpr
for information on how it works. See
print
for information on our local intelligent print command.
mkdir
Use this command to create a directory.
% mkdir essays
To get "into" this directory, do
% cd essays
To see what files are in
essays, do this:
% ls
There shouldn't be any files there yet, since you just made
it. To create files, see
cat
or
emacs.
more
More is a command used to read text files. For example, we
could do this:
% more poems
The effect of this to let you read the file "poems
". It probably will not fit in one screen, so you need
to know how to "turn pages". Here are the basic
commands:
-
q --- quit more
-
spacebar --- read next page
-
return key --- read next line
-
b --- go back one page
For still more information, use the command
man more.
mv
Use this command to change the name of file and directories.
% mv foo foobar
The file that was named
foo is now named
foobar
ncftp
Use
ncftp for anonymous ftp ---
that means you don't have to have a password.
% ncftp ftp.fubar.net
Connected to ftp.fubar.net
> get jokes.txt
The file
jokes.txt is downloaded from
the machine
ftp.fubar.net.
print
This is a moderately intelligent print command.
% print foo
% print notes.ps
% print manuscript.dvi
In each case
print does the right thing, regardless
of whether the file is a text file (like
foo ), a
postcript file (like
notes.ps, or a dvi file (like
manuscript.dvi. In these examples the file is
printed on the default printer. To see what this is, do
% print
and read the message displayed. To print on a specific printer,
do this:
% print foo jwb321
% print notes.ps jwb321
% print manuscript.dvi jwb321
To change the default printer, do this:
% setenv PRINTER jwb321
pwd
Use this command to find out what directory you are working in.
% pwd
/u/ma/jeremy
% cd homework
% pwd
/u/ma/jeremy/homework
% ls
assign-1 assign-2 assign-3
% cd
% pwd
/u/ma/jeremy
%
Jeremy began by working in his "home" directory.
Then he
cd
'd into his homework subdirectory. Cd means "
change directory". He used pwd to check to make sure
he was in the right place, then used
ls to see if all
his homework files were there. (They were). Then he
cd'd back to his home directory.
rm
Use
rm to remove files from your directory.
% rm foo
remove foo? y
% rm letter*
remove letter1? y
remove letter2? y
remove letter3? n
%
The first command removed a single file. The second command
was intended to remove all files beginning with the string
"letter." However, our user (Jeremy?) decided not
to remove letter3.
rmdir
Use this command to remove a directory. For example, to
remove a directory called "essays", do this:
% rmdir essays
A directory must be empty before it can be removed. To
empty a directory, use
rm.
rsh
Use this command if you want to work on a computer different
from the one you are currently working on. One reason to do
this is that the remote machine might be faster. For
example, the command
% rsh solitude
connects you to the machine
solitude. This is one
of our public workstations and is fairly fast.
See also:
telnet
setenv
% echo $PRINTER
labprinter
% setenv PRINTER myprinter
% echo $PRINTER
myprinter
sort
Use this commmand to sort a file. For example, suppose we have
a file
dict with contents
red rojo
green verde
blue azul
white blanco
black negro
Then we can do this:
% sort dict
black negro
blue azul
green verde
red rojo
white blanco
Here the output of
sort went to the screen. To store
the output in file we do this:
% sort dict >dict.sorted
You can check the contents of the file
dict.sorted
using
cat
,
more
, or
emacs
.
tail
Use this command to look at the tail of a file. For example,
% tail essay.001
displays the last 10 lines of the file
essay.001 To
see a specific number of lines, do this:
% tail -n 20 essay.001
This displays the last 20 lines of the file.
tar
Use create compressed archives of directories and files,
and also to extract directories and files from an archive.
Example:
% tar -tvzf foo.tar.gz
displays the file names in the compressed archive
foo.tar.gz
while
% tar -xvzf foo.tar.gz
extracts the files.
telnet
Use this command to log in to another machine from the
machine you are currently working on. For example, to log
in to the machine "solitude", do this:
% telnet solitude
See also:
rsh.
wc
Use this command to count the number of characters, words,
and lines in a file. Suppose, for example, that we have a
file
dict with contents
red rojo
green verde
blue azul
white blanco
black negro
Then we can do this
% wc dict
5 10 56 tmp
This shows that
dict has 5 lines, 10 words, and 56
characters.
The word count command has several options, as illustrated
below:
% wc -l dict
5 tmp
% wc -w dict
10 tmp
% wc -c dict
56 tmp
dummy
Under construction
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