Basic Unix Commands-----1

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

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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.

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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.

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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.

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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.

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date

Use this command to check the date and time.

   % date

Fri Jan  6 08:52:42 MST 1995

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