Microsoft Word – Document1
Unix Command Summary
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
%
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
%
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!