Unix commands-2

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

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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.

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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

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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 -20 essay.001

This displays the first 20 lines of the file.

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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.

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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.

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