Using UNIX

Case sensitivity
cat - printing file(s) to screen
Changing Password
C and C++ compilers
Communication Software
Deleting a file - rm
Directory listing: ls
Directory operations
- Change directory: cd
- Copy a file: cp
- Create subdirectory: mkdir
- Move a file: mv
- Print name of current directory: pwd
- Remove subdirectory: rmdir
- Rename a file: mv

Editing a File
E-mail
FTP - copy a file between computers
Interrupting a program
Introduction
Help - the man command
ls - listing files in directory
man - the help command
more - printing file to screen with pause
Password, changing
Pipelining - combining operations
Printing onscreen - cat and more
Recording your screen: script
rm - "remove" - deleting a file
Script files - recording your screen
Telnet

"cis" (full name: "cis.niagara.edu") is a computer that uses the UNIX operating system and is available to all Niagara students. UNIX is an operating system that, in many respects, is very nice to use, but its notation takes some getting used to. In particular, the names of many of its utility programs are very different from their analogs' in other operating systems that Niagara students may use, such Windows or DOS.

CASE SENSITIVITY: One important difference between UNIX and some other operating systems is that UNIX is case-sensitive (i.e., it matters whether the letter you type is capitalized or in lower case) in command names and file names, while Windows and DOS are not. For example, if you have a file in UNIX stored under the name "proj1.cc", you may not refer to that file as "PROJ1.CC" or as "Proj1.cc".

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INTERRUPTING A PROGRAM/PROCESS: Most programs and processes running under Unix may be interrupted or "broken" via ^c (control-c). For example, a student testing her/his computer program may find that the program is caught in an infinite loop. It would be useful to interrupt the program with ^c.

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CHANGING YOUR PASSWORD: The command that initiates the process of changing your password is

     passwd

After you give this command, you are prompted for, and should enter, your current password. What you type for a password in this and the next two steps will not show up on your screen, to protect you from the wandering eyes of one who might be tempted to penetrate your account.
You are then prompted for, and should enter, your desired (new) password.
To protect against typing errors, you are prompted for, and should again enter, your new password. If the two entries for your new password agree, your password is correspondingly changed immediately.

In some versions of Unix, passwords may be required to satisfy properties such as

minimum of 6 characters;
at least one non-letter character;
certain characters not permitted (typically, the space and the ampersand, "&");
there may be a requirement that one of the characters be a capital letter;
there may be a requirement that your password not look like an English word.

After you change your password, it's a good idea to logout, then login again immediately. This helps imprint in your memory that you have changed your password. To index
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EDITING a FILE: The vi editor is available on cis and other Unix systems. Also available is the pico editor familiar to users of Pine e-mail.

NOTE: Unlike VMS (until recently available to Niagara users on the VAX), UNIX replaces old files with new versions -- it doesn't automatically save old versions as backups. If you wish to save an old version, use "mv" (to rename, as described below) or "cp" (copy).

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COMMUNICATIONS SOFTWARE in UNIX: Mail, talk, Telnet, and FTP are available on many Unix systems.

"Pine," an e-mail package, is invoked via the command
```
     pine       (lower case letters)
```
Pine is menu-driven, hence should be fairly easy to figure out. If, however, you prefer explicit to empirical learning about Pine, click here.
You may use FTP to copy a file from one computer to another. You may establish an FTP connection from the Niagara network of PCs to cis.niagara.edu via
```
   ftp cis
```
and then upload/download a file as described. At the current writing, cis is not directly connected to a printer available to most users, so this is a good way to print cis files -- FTP them to another computer from which you can print.
If you have login permission on another Internet computer, you may also use FTP to establish a connection from cis to the other computer and use FTP to copy files between these computers.

By using communications software, it is easy to prepare a file such as a C++ program on one computer and use it on another.

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COMPILING a C or C++ PROGRAM: See this link.

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GETTING HELP: The UNIX "help" command is "man" (for "manual" -- the on-line help often is just a verbatim copy of explanations that may be found in UNIX manuals). Use it in the form

    man command

to get information on the "command". For example, to get more information on the C++ compiler, use

    man gcc    or    man cc

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SCRIPT FILES: This allows you to record what appears on your screen. To start a script file, use a command of the form

     script file-name

-- for example,

     script p1s

starts a script file called "p1s". This begins the process of recording what appears on your screen until you stop the recording process, so you now take whatever actions you wish to record, e.g., running a program to demonstrate to your instructor how your project works. When you are ready to stop the recording, strike ^d (control-d). This will stop the recording. You may then use either FTP or Windows copy-and-paste operations to copy the script file to your PC in order to print it. To index
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PRINTING a file on screen:

The "more" command, used in the form

   more filename

will print the file on your screen, one screen at a time. When it pauses, you may respond via

     space             to print the next screen;
     return            to print the next line;
     q                 to quit.

The "cat" command may be used to print one or several files on the screen, without pausing (as "more" pauses) for a user to read the screen and signal continuation. Thus, "cat" might typically used to print files within a script file. E.g.,
```
          cat proj2.dat
```
will print the file named "proj2.dat";
```
          cat proj2.cc proj2.dat proj2.x
```
will print the files "proj2.cc", "proj2.dat", and "proj2.x" on the screen.

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LISTING YOUR DIRECTORY: use

   ls               to get a list of files in the directory, or
   ls -l            to get a list of files and associated data.

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DELETING A FILE: use

   rm filename

to "remove" the file from your directory. The asterisk (*) may be used (as in Windows, DOS) as a wildcard, e.g.,

   rm *          removes all files in the current directory
   rm a*.txt     removes all files with first letter "a" in the
                   filename and with extension ".txt"
   rm blah.hm    removes the file named "blah.hm"

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DIRECTORY OPERATIONS:

CREATE A SUBDIRECTORY via a command of the form

          mkdir directory-name       ("mkdir" - "make directory")

REMOVE (DELETE) AN EMPTY DIRECTORY via a command of the form
```
          rmdir directory-name
```

CHANGE DIRECTORY via "cd". Some examples:

cd             to go to user's root directory
cd sub1        to go to "sub1" subdirectory of current directory
cd sub1/sub2   to go to "sub1" subdirectory of current directory and
                   then to "sub2" subdirectory of "sub1" subdirectory
cd ..          to go up one level
cd ~/blah      to go to "blah" subdirectory of root directory

PRINT THE WORKING DIRECTORY (identify which directory you're currently working in) via
```
          pwd
```

RENAME A FILE via "mv" ("move") in the form
```
   mv oldfilename newfilename
```
MOVE A FILE to a different directory via "mv" in the form
```
   mv filename destinationdirectory
```
For example,
```
   mv proj1.cc cpp-files/cis265
```
will move the file "proj1.cc" from the current directory to the "cpp-files" subdirectory of the current directory - indeed, to the "cis265" subdirectory of the "cpp-files" directory.
```
   mv sample.dat ~/projdata
```
will move "sample.dat" from the current directory to the root (indicated by the "~") directory's "projdata" subdirectory.
COPY A FILE via "cp". Examples:
- Within the same directory: use the form
```
          cp source-file-name destination-file-name
```
  E.g.,
```
          cp proj3.cc proj3.bak
```
  makes a copy of "proj3.cc" under the filename "proj3.bak".
- To copy a file from another directory to the current directory, use the form
```
          cp remote-directory/filename .  (the period
                                           means "here")
```
  E.g.,
```
          cp abc/survey.dat .
```
  copies the file "survey.dat" from the "abc" subdirectory to the current directory.
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PIPELINING: Unix allows processes to be "pipelined" so that a single command may be given that directs a sequence of processes such that output from one process is to be used as input for the next process. The pipe symbol (sometimes called the "broken pipe"), "|", is used for this purpose.

An example: Suppose you wish to study your directory via
```
          ls -l
```
but the directory is too large to fit on one computer screen. You may apply "more" to the directory via
```
          ls -l | more
```
which may be interpreted as follows: the command "ls -l" prepares the display of a directory (which ordinarily would immediately be printed on the screen). If, instead, we pipeline the result of "ls -l" through "more", the directory display is taken to be the input file of "more". Try it.
Multiple pipes may be used with a single command. Thus, to direct program "a" to produce output that will be used as input by program "b", which in turn produces output that is used as input to program "c", use
```
          a | b | c
```
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