Unix commands-3

Unix commands-3

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. 

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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.

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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 

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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.

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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 (likemanuscript.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

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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.

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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.

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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. 

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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 

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setenv

   % echo $PRINTER

     labprinter

   % setenv PRINTER myprinter

   % echo $PRINTER

     myprinter

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sort

Use this commmand to sort a file. For example, suppose we have a filedict 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 , oremacs .

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tail

Use this command to look at the tail of a file. For example,

   % head essay.001

displays the last 10 lines of the file essay.001 To see a specific number of lines, do this:

   % head -20 essay.001

This displays the last 20 lines of the file.

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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.

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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. 

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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