Computer Files

1
Computer Files

• Stored on disks, CDs, tapes, in memory.
• Types of files plain text, formatted (.doc .xls
  etc), binary (executable).
• A disk has a directory structure.
• Top level (root) directory, with
• Files in it
• Subdirectories in it.

2
UNIX File Commands

• ls -- list files.
• cd -- change directory.
• mkdir -- make new directory.
• rmdir -- delete directory.
• mv -- move a file.
• cp -- copy a file.
• rm -- remove (delete) a file.

3
Using Telnet

• A protocol (set of rules)
• Connects your machine to another.
• Can be used to log in to a machine.
• Uses TCP to correct errors

4
Uses of Telnet

• Logging in to remote machines
• Can connect to other services, but the logins
  wont always work.
• Web servers -- www.umd.edu 80
• GET /index.html
• ftp servers -- ftp.sf.net 21
• Echo servers -- wolfe.umd.edu 12345

5
Intro to File Transfers

• Name ftp (File Transfer Protocol)
• Also lets you connect to machines
• Client-Server architecture
• The command is called ftp
• ftp listens on port 21,
• Lets you transfer/download/upload files like
• MP3s, pictures, letters, programs

6
Transfer Modes

• There are two transfer modes text and binary.
• Text is for files like funfile.
• Binary is for files like music, pictures, Word
  documents, computer programs.
• Not using binary can cause subtle errors, such as
  1out of 40 pictures not working.

7
Data Transfers

• In text mode, files may be altered to work with
  the recipient machine.
• Binary files are not altered at all.
• Typing bin changes to binary mode.
• Typing asc changes to text mode.

8
Using ftp 1

• The command to use ftp is -- ftp
• You can type the host (server) name in the
  command prompt, or at the ftpgt prompt.
• Some sites are anonymous, no login required and
  give you limited access.
• Some sites require a login and password.

9
Ftp Commands

• Get to move a file to your computer.
• Put to move a file from your computer.
• You are in a certain directory location on both
  machines. You can use cd and lcd (local change
  dir) to move around in the directory tree. You
  can use ls to see the contents of the remote
  directory.
• !ltcommandgt does a local command.

10
Ftp Commands 2

• ls -- list files in the remote directory.
• cd -- change remote directory.
• cdup -- remote directory up one level.
• lcd -- change local directory.
• ? Or help -- list helpful keywords.
• close or quit -- disconnect from the server.

11
Getting files

• recv ltfilenamegt
• recv ltfilenamegt ltnew-filenamegt
• get ltfilenamegt
• get ltfilenamegt ltnew-filenamegt
• mget ltlist_of_remote_filesgt
• get and recv do the same thing.

12
Sending Files

• send ltfilenamegt
• send ltfilenamegt ltnew_filenamegt
• put ltfilenamegt
• put ltfilenamegt ltnew_filenamegt
• mput ltlist_of_local_filesgt
• send and put do the same thing.

13
Ftp speed

• Depends on
• Your connection speed.
• Server connection speed.
• Your computers load.
• The server load.
• General Internet traffic.
• Restraints your ISP puts on you.

14
Other ways to transfer

• Kermit, z-modem, x-modem these only send one
  way.
• Other ftp programs within your computer.
• Downloading files within a web browser.
• Using special terminal/communications programs
  with special file transfer code.
• Example Wsftp on WAM NT machines.

15
Anonymous ftp

• Some sites dont require logins
• Similar to downloading from a website without
  logging in .
• Login as anonymous
• Send email address as password
• You may not get access to everything.
• Example ftp ftp.sf.net

16
Anonymous ftp

• Anonymous logins not available always.
• You cannot always write files to the server.
• However, there may be an incoming or uploads
  directory where you can post files.

17
Victor

• Online card catalog
• Type telnet victor
• No login needed
• Type pac (public access catalog)
• Choose terminal type
• vt100 usually works
• //exit hangs up

18
Databases on Victor

• USM campus catalogs
• Other libraries in MD.
• Out-of-state libraries.
• Periodicals index
• Other kinds of databases.
• 2 USM catalogs
• 59 UMCP catalogs

19
Some types of searches

• Name search -- search for an author or editor
  or books on an author.
• Word search -- search for strings of words such
  as in a title.
• Subject Word -- search for keywords only.

20
Victor Searches

• Browse -- try to match similar keywords, numbers
  or series names.
• Title search tries to match a title if it can.
• Series search is used for journals or series of
  technical books. (eg. Lecture notes in
  mathematics.)
• Call number search is used if you know the
  approximate call number. (eg. Qa403)

21
Newsgroups

• rn To start newsreader at prompt
• Other readers trn tin nn readnews
• Google groups for WWW access.
• May ask if you want to subscribe.
• Type N generally
• Type y if you want to subscribe then enter when
  the .Lq option comes up.
• Two levels group and article selection.

22
Newsgroup Selection

• Ask if you want to read a group ynq
• Y or space means read, n no/next, q quit rn.
• Type g groupname to start reading a group.
• Eg. g alt.test
• u means unsubscribe a group.
• ! execute shell command.
• /ltpatterngt search for group containing this
  pattern.

23
Article Selection Level 1

• space read next article
• q quit this group.
• N scan for next article with same title.
• n read next article.
• p read previous article.

24
Article Selection Level 2

• /ltpatterngt/h scan for pattern in header.
• /ltpatterngt/a scan for pattern in article.
• F or f send a reply post.
• R or r reply to poster in email.
• s file save this article to a file.
• Hit enter when asked about mailbox format.
• It will be saved to your News directory.

25
Pnews 1

• Pnews post an article to a newsgroup.
• Asks for newsgroup(s) List them.
• Eg. alt.test
• Distribution
• Choose any, (UM is good for alt.test)
• Title/Subject Enter the subject.
• Are you sure? Y

26
Pnews 2

• Prepared file to include?
• Useful if you pre-write using a good editor.
• Editor hit enter (should start pico).
• Write the message and hit X when done.
• Options Send, Abort, Edit, List
• Choose s for send if youre happy with the post.