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Showing posts with label Linux / Unix Command. Show all posts
Showing posts with label Linux / Unix Command. Show all posts

Sunday, September 9, 2012

List of bash command and with description, Linux command line Questions, Answers for Interview preparation



Linux command line Questions &Answers for Interview preparation


  1. You need to see the last fifteen lines of the files dog, cat and horse. What command should you use? tail -15 dog cat horse
    The tail utility displays the end of a file. The -15 tells tail to display the last fifteen lines of each specified file.
  2. Who owns the data dictionary?
    The SYS user owns the data dictionary. The SYS and SYSTEM users are created when the database is created.
  3. You routinely compress old log files. You now need to examine a log from two months ago. In order to view its contents without first having to decompress it, use the _________ utility.
    zcat
    The zcat utility allows you to examine the contents of a compressed file much the same way that cat displays a file.
  4. You suspect that you have two commands with the same name as the command is not producing the expected results. What command can you use to determine the location of the command being run?
    which
    The which command searches your path until it finds a command that matches the command you are looking for and displays its full path.
  5. You locate a command in the /bin directory but do not know what it does. What command can you use to determine its purpose.
    whatis
    The whatis command displays a summary line from the man page for the specified command.
  6. You wish to create a link to the /data directory in bob’s home directory so you issue the command ln /data /home/bob/datalink but the command fails. What option should you use in this command line to be successful.
    Use the -F option
    In order to create a link to a directory you must use the -F option.
  7. When you issue the command ls -l, the first character of the resulting display represents the file’s ___________.
    type
    The first character of the permission block designates the type of file that is being displayed.
  8. What utility can you use to show a dynamic listing of running processes? __________
    top
    The top utility shows a listing of all running processes that is dynamically updated.
  9. Where is standard output usually directed?
    to the screen or display
    By default, your shell directs standard output to your screen or display.
  10. You wish to restore the file memo.ben which was backed up in the tarfile MyBackup.tar. What command should you type?
    tar xf MyBackup.tar memo.ben
    This command uses the x switch to extract a file. Here the file memo.ben will be restored from the tarfile MyBackup.tar.
  11. You need to view the contents of the tarfile called MyBackup.tar. What command would you use?
    tar tf MyBackup.tar
    The t switch tells tar to display the contents and the f modifier specifies which file to examine.
  12. You want to create a compressed backup of the users’ home directories. What utility should you use?
    tar
    You can use the z modifier with tar to compress your archive at the same time as creating it.
  13. What daemon is responsible for tracking events on your system?
    syslogd
    The syslogd daemon is responsible for tracking system information and saving it to specified log files.
  14. You have a file called phonenos that is almost 4,000 lines long. What text filter can you use to split it into four pieces each 1,000 lines long?
    split
    The split text filter will divide files into equally sized pieces. The default length of each piece is 1,000 lines.
  15. You would like to temporarily change your command line editor to be vi. What command should you type to change it?
    set -o vi
    The set command is used to assign environment variables. In this case, you are instructing your shell to assign vi as your command line editor. However, once you log off and log back in you will return to the previously defined command line editor.
  16. What account is created when you install Linux?
    root
    Whenever you install Linux, only one user account is created. This is the superuser account also known as root.
  17. What command should you use to check the number of files and disk space used and each user’s defined quotas?
    repquota
    The repquota command is used to get a report on the status of the quotas you have set including the amount of allocated space and amount of used space.

  List of bash command line and with description

  A-Z Index 

  alias    Create an alias •
  apropos  Search Help manual pages (man -k)
  apt-get  Search for and install software packages (Debian/Ubuntu)
  aptitude Search for and install software packages (Debian/Ubuntu)
  aspell   Spell Checker
  awk      Find and Replace text, database sort/validate/index
b
  basename Strip directory and suffix from filenames
  bash     GNU Bourne-Again SHell 
  bc       Arbitrary precision calculator language 
  bg       Send to background
  break    Exit from a loop •
  builtin  Run a shell builtin
  bzip2    Compress or decompress named file(s)
c
  cal      Display a calendar
  case     Conditionally perform a command
  cat      Concatenate and print (display) the content of files
  cd       Change Directory
  cfdisk   Partition table manipulator for Linux
  chgrp    Change group ownership
  chmod    Change access permissions
  chown    Change file owner and group
  chroot   Run a command with a different root directory
  chkconfig System services (runlevel)
  cksum    Print CRC checksum and byte counts
  clear    Clear terminal screen
  cmp      Compare two files
  comm     Compare two sorted files line by line
  command  Run a command - ignoring shell functions •
  continue Resume the next iteration of a loop •
  cp       Copy one or more files to another location
  cron     Daemon to execute scheduled commands
  crontab  Schedule a command to run at a later time
  csplit   Split a file into context-determined pieces
  cut      Divide a file into several parts
d
  date     Display or change the date & time
  dc       Desk Calculator
  dd       Convert and copy a file, write disk headers, boot records
  ddrescue Data recovery tool
  declare  Declare variables and give them attributes •
  df       Display free disk space
  diff     Display the differences between two files
  diff3    Show differences among three files
  dig      DNS lookup
  dir      Briefly list directory contents
  dircolors Colour setup for `ls'
  dirname  Convert a full pathname to just a path
  dirs     Display list of remembered directories
  dmesg    Print kernel & driver messages 
  du       Estimate file space usage
e
  echo     Display message on screen •
  egrep    Search file(s) for lines that match an extended expression
  eject    Eject removable media
  enable   Enable and disable builtin shell commands •
  env      Environment variables
  ethtool  Ethernet card settings
  eval     Evaluate several commands/arguments
  exec     Execute a command
  exit     Exit the shell
  expect   Automate arbitrary applications accessed over a terminal
  expand   Convert tabs to spaces
  export   Set an environment variable
  expr     Evaluate expressions
f
  false    Do nothing, unsuccessfully
  fdformat Low-level format a floppy disk
  fdisk    Partition table manipulator for Linux
  fg       Send job to foreground 
  fgrep    Search file(s) for lines that match a fixed string
  file     Determine file type
  find     Search for files that meet a desired criteria
  fmt      Reformat paragraph text
  fold     Wrap text to fit a specified width.
  for      Expand words, and execute commands
  format   Format disks or tapes
  free     Display memory usage
  fsck     File system consistency check and repair
  ftp      File Transfer Protocol
  function Define Function Macros
  fuser    Identify/kill the process that is accessing a file
g
  gawk     Find and Replace text within file(s)
  getopts  Parse positional parameters
  grep     Search file(s) for lines that match a given pattern
  groupadd Add a user security group
  groupdel Delete a group
  groupmod Modify a group
  groups   Print group names a user is in
  gzip     Compress or decompress named file(s)
h
  hash     Remember the full pathname of a name argument
  head     Output the first part of file(s)
  help     Display help for a built-in command •
  history  Command History
  hostname Print or set system name
i
  iconv    Convert the character set of a file
  id       Print user and group id's
  if       Conditionally perform a command
  ifconfig Configure a network interface
  ifdown   Stop a network interface 
  ifup     Start a network interface up
  import   Capture an X server screen and save the image to file
  install  Copy files and set attributes
j
  jobs     List active jobs •
  join     Join lines on a common field
k
  kill     Stop a process from running
  killall  Kill processes by name
l
  less     Display output one screen at a time
  let      Perform arithmetic on shell variables •
  ln       Make links between files
  local    Create variables •
  locate   Find files
  logname  Print current login name
  logout   Exit a login shell •
  look     Display lines beginning with a given string
  lpc      Line printer control program
  lpr      Off line print
  lprint   Print a file
  lprintd  Abort a print job
  lprintq  List the print queue
  lprm     Remove jobs from the print queue
  ls       List information about file(s)
  lsof     List open files
m
  make     Recompile a group of programs
  man      Help manual
  mkdir    Create new folder(s)
  mkfifo   Make FIFOs (named pipes)
  mkisofs  Create an hybrid ISO9660/JOLIET/HFS filesystem
  mknod    Make block or character special files
  more     Display output one screen at a time
  mount    Mount a file system
  mtools   Manipulate MS-DOS files
  mtr      Network diagnostics (traceroute/ping)
  mv       Move or rename files or directories
  mmv      Mass Move and rename (files)
n
  netstat  Networking information
  nice     Set the priority of a command or job
  nl       Number lines and write files
  nohup    Run a command immune to hangups
  notify-send  Send desktop notifications
  nslookup Query Internet name servers interactively
o
  open     Open a file in its default application
  op       Operator access 
p
  passwd   Modify a user password
  paste    Merge lines of files
  pathchk  Check file name portability
  ping     Test a network connection
  pkill    Stop processes from running
  popd     Restore the previous value of the current directory
  pr       Prepare files for printing
  printcap Printer capability database
  printenv Print environment variables
  printf   Format and print data •
  ps       Process status
  pushd    Save and then change the current directory
  pwd      Print Working Directory
q
  quota    Display disk usage and limits
  quotacheck Scan a file system for disk usage
  quotactl Set disk quotas
r
  ram      ram disk device
  rcp      Copy files between two machines
  read     Read a line from standard input •
  readarray Read from stdin into an array variable •
  readonly Mark variables/functions as readonly
  reboot   Reboot the system
  rename   Rename files
  renice   Alter priority of running processes 
  remsync  Synchronize remote files via email
  return   Exit a shell function
  rev      Reverse lines of a file
  rm       Remove files
  rmdir    Remove folder(s)
  rsync    Remote file copy (Synchronize file trees)
s
  screen   Multiplex terminal, run remote shells via ssh
  scp      Secure copy (remote file copy)
  sdiff    Merge two files interactively
  sed      Stream Editor
  select   Accept keyboard input
  seq      Print numeric sequences
  set      Manipulate shell variables and functions
  sftp     Secure File Transfer Program
  shift    Shift positional parameters
  shopt    Shell Options
  shutdown Shutdown or restart linux
  sleep    Delay for a specified time
  slocate  Find files
  sort     Sort text files
  source   Run commands from a file `.'
  split    Split a file into fixed-size pieces
  ssh      Secure Shell client (remote login program)
  strace   Trace system calls and signals
  su       Substitute user identity
  sudo     Execute a command as another user
  sum      Print a checksum for a file
  suspend  Suspend execution of this shell •
  symlink  Make a new name for a file
  sync     Synchronize data on disk with memory
t
  tail     Output the last part of file
  tar      Tape ARchiver
  tee      Redirect output to multiple files
  test     Evaluate a conditional expression
  time     Measure Program running time
  times    User and system times
  touch    Change file timestamps
  top      List processes running on the system
  traceroute Trace Route to Host
  trap     Run a command when a signal is set(bourne)
  tr       Translate, squeeze, and/or delete characters
  true     Do nothing, successfully
  tsort    Topological sort
  tty      Print filename of terminal on stdin
  type     Describe a command •
u
  ulimit   Limit user resources •
  umask    Users file creation mask
  umount   Unmount a device
  unalias  Remove an alias •
  uname    Print system information
  unexpand Convert spaces to tabs
  uniq     Uniquify files
  units    Convert units from one scale to another
  unset    Remove variable or function names
  unshar   Unpack shell archive scripts
  until    Execute commands (until error)
  uptime   Show uptime
  useradd  Create new user account
  userdel  Delete a user account
  usermod  Modify user account
  users    List users currently logged in
  uuencode Encode a binary file 
  uudecode Decode a file created by uuencode
v
  v        Verbosely list directory contents (`ls -l -b')
  vdir     Verbosely list directory contents (`ls -l -b')
  vi       Text Editor
  vmstat   Report virtual memory statistics
w
  wait     Wait for a process to complete •
  watch    Execute/display a program periodically
  wc       Print byte, word, and line counts
  whereis  Search the user's $path, man pages and source files for a program
  which    Search the user's $path for a program file
  while    Execute commands
  who      Print all usernames currently logged in
  whoami   Print the current user id and name (`id -un')
  wget     Retrieve web pages or files via HTTP, HTTPS or FTP
  write    Send a message to another user 
x
  xargs    Execute utility, passing constructed argument list(s)
  xdg-open Open a file or URL in the user's preferred application.
  yes      Print a string until interrupted
  .        Run a command script in the current shell
  !!       Run the last command again
  ###      Comment / Remark
Commands marked • are bash built-ins, these are available under all shells.

to further know them using syntax search option .. click here

Saturday, September 1, 2012

Linux / Unix Command: vi, vim, gvim Command Library

Linux / Unix Command: vi, vim, gvim
Command Library

SYNOPSIS

    % vi [options] [file ..]

DESCRIPTION

    The "vi" text editor is not recommended for newbies.
    To exit vi (no changes saved) use these five characters: <ESC>:q!<Enter>.
    vim: Modern Linux distributions use vim (="vi improved") in place of vi, and vim is somewhat better than the original vi.
    gvim: The GUI version of vi is also available: type gvim in an X terminal.
    The most important thing to understand about vi is that is a "modal" editor, i.e., it has a few modes of operation among which user must switch. (The same keystrokes have different effects in different modes.) The quick reference is below, with the 4 essential commands in red.

    The commands to switch modes:

The key
    Enters the mode     Remarks
<ESC>     command mode     (get back to the command mode from any editing mode)
i     "insert" editing mode     (start inserting before the current position of the cursor)

    DO NOT PRESS ANY OTHER KEYES IN THE COMMAND MODE. THERE ARE MORE COMMANDS AND MODES IN THE COMMAND MODE!

    Copying, cutting and pasting (in the command mode):
    v start highlighting text. Then, move the cursor to highlight text
    y copy highlighted text
    x cut highlighted text
    p paste text that has been cut/copied

    Saving and quitting (from the command mode):
    :w write (=save)
    :w filename write the contents to the file "filename"
    :x save and exit
    :q quit (it won't let you if changes not saved)
    :q! quit discarding changes (you will not be prompted if changes not saved)

EXAMPLE

    % vi parse_record.pl

    Starts vi with the default settings and opens file parse_record.pl.

Important: Use the man command (% man) to see how a command is used on your particular computer.

How to download files (video, mp3, mp4, avi,pdf etc) on Linux open terminal usig command (ubuntu 12.10)

How to download files (video, mp3, mp4, avi,pdf etc) on Linux open terminal using command (ubuntu 12.10)


CTRL+ALT+T to open terminal
example:
vina@vinay:/media/backup$ wget -r -l0 wapmint.com/datas/load/Games/Nokia%20Games/Java%20Games%20Collection/PipeDream.jar

Linux / Unix Command: wget
Command Library

Action     Command
Download file     wget http://link-to-file
Resumable Downloads     wget -c http://link-to-file
Download Entire Website     wget -r http://link-to-site
Download Only PDFs from a page     wget -A.pdf -r -l1 -nd --no-parent http://link-to-webpage
Download Only mp3 files from a page     wget -A.mp3 -r -l1 -nd --no-parent http://link-to-webpage
Donot Download mp3 files from a page     wget -R.mp3 -r -l1 -nd --no-parent http://link-to-webpage
Ignore robots.txt     wget -erobots=off http://link-to-fileordirectory
Limit download Speed in kbps     wget --limit-rate=20 http://url-to-fileorwebsite
Mask as firefox or act as firefox     wget -U Mozilla http://your-link-to/file



NAME
wget - GNU Wget Manual
SYNOPSIS
wget [option]... [URL]...
EXAMPLES
DESCRIPTION
GNU Wget is a free utility for non-interactive download of files from the Web. It supports HTTP, HTTPS, and FTP protocols, as well as retrieval through HTTP proxies.

Wget is non-interactive, meaning that it can work in the background, while the user is not logged on. This allows you to start a retrieval and disconnect from the system, letting Wget finish the work. By contrast, most of the Web browsers require constant user's presence, which can be a great hindrance when transferring a lot of data.

Wget can follow links in HTML pages and create local versions of remote web sites, fully recreating the directory structure of the original site. This is sometimes referred to as ``recursive downloading.'' While doing that, Wget respects the Robot Exclusion Standard (/robots.txt). Wget can be instructed to convert the links in downloaded HTML files to the local files for offline viewing.

Wget has been designed for robustness over slow or unstable network connections; if a download fails due to a network problem, it will keep retrying until the whole file has been retrieved. If the server supports regetting, it will instruct the server to continue the download from where it left off.
-V
--version
    Display the version of Wget.
-h
--help
    Print a help message describing all of Wget's command-line options.
-b
--background
    Go to background immediately after startup. If no output file is specified via the -o, output is redirected to wget-log.
-e command
--execute command
    Execute command as if it were a part of .wgetrc. A command thus invoked will be executed after the commands in .wgetrc, thus taking precedence over them.

Logging and Input File Options

-o logfile
--output-file=logfile
    Log all messages to logfile. The messages are normally reported to standard error.
-a logfile
--append-output=logfile
    Append to logfile. This is the same as -o, only it appends to logfile instead of overwriting the old log file. If logfile does not exist, a new file is created.
-d
--debug
    Turn on debug output, meaning various information important to the developers of Wget if it does not work properly. Your system administrator may have chosen to compile Wget without debug support, in which case -d will not work. Please note that compiling with debug support is always safe---Wget compiled with the debug support will not print any debug info unless requested with -d.
-q
--quiet
    Turn off Wget's output.
-v
--verbose
    Turn on verbose output, with all the available data. The default output is verbose.
-nv
--non-verbose
    Non-verbose output---turn off verbose without being completely quiet (use -q for that), which means that error messages and basic information still get printed.
-i file
--input-file=file
    Read URLs from file, in which case no URLs need to be on the command line. If there are URLs both on the command line and in an input file, those on the command lines will be the first ones to be retrieved. The file need not be an HTML document (but no harm if it is)---it is enough if the URLs are just listed sequentially.

    However, if you specify --force-html, the document will be regarded as html. In that case you may have problems with relative links, which you can solve either by adding "" to the documents or by specifying --base=url on the command line.
-F
--force-html
    When input is read from a file, force it to be treated as an HTML file. This enables you to retrieve relative links from existing HTML files on your local disk, by adding "" to HTML, or using the --base command-line option.
-B URL
--base=URL
    When used in conjunction with -F, prepends URL to relative links in the file specified by -i.

Download Options

--bind-address=ADDRESS
    When making client TCP/IP connections, "bind()" to ADDRESS on the local machine. ADDRESS may be specified as a hostname or IP address. This option can be useful if your machine is bound to multiple IPs.
-t number
--tries=number
    Set number of retries to number. Specify 0 or inf for infinite retrying.
-O file
--output-document=file
    The documents will not be written to the appropriate files, but all will be concatenated together and written to file. If file already exists, it will be overwritten. If the file is -, the documents will be written to standard output. Including this option automatically sets the number of tries to 1.
-nc
--no-clobber
    If a file is downloaded more than once in the same directory, Wget's behavior depends on a few options, including -nc. In certain cases, the local file will be clobbered, or overwritten, upon repeated download. In other cases it will be preserved.

    When running Wget without -N, -nc, or -r, downloading the same file in the same directory will result in the original copy of file being preserved and the second copy being named file.1. If that file is downloaded yet again, the third copy will be named file.2, and so on. When -nc is specified, this behavior is suppressed, and Wget will refuse to download newer copies of file. Therefore, ``"no-clobber"'' is actually a misnomer in this mode---it's not clobbering that's prevented (as the numeric suffixes were already preventing clobbering), but rather the multiple version saving that's prevented.

    When running Wget with -r, but without -N or -nc, re-downloading a file will result in the new copy simply overwriting the old. Adding -nc will prevent this behavior, instead causing the original version to be preserved and any newer copies on the server to be ignored.

    When running Wget with -N, with or without -r, the decision as to whether or not to download a newer copy of a file depends on the local and remote timestamp and size of the file. -nc may not be specified at the same time as -N.

    Note that when -nc is specified, files with the suffixes .html or (yuck) .htm will be loaded from the local disk and parsed as if they had been retrieved from the Web.
-c
--continue
    Continue getting a partially-downloaded file. This is useful when you want to finish up a download started by a previous instance of Wget, or by another program. For instance:

            wget -c ftp://sunsite.doc.ic.ac.uk/ls-lR.Z

    If there is a file named ls-lR.Z in the current directory, Wget will assume that it is the first portion of the remote file, and will ask the server to continue the retrieval from an offset equal to the length of the local file.

    Note that you don't need to specify this option if you just want the current invocation of Wget to retry downloading a file should the connection be lost midway through. This is the default behavior. -c only affects resumption of downloads started prior to this invocation of Wget, and whose local files are still sitting around.

    Without -c, the previous example would just download the remote file to ls-lR.Z.1, leaving the truncated ls-lR.Z file alone.

    Beginning with Wget 1.7, if you use -c on a non-empty file, and it turns out that the server does not support continued downloading, Wget will refuse to start the download from scratch, which would effectively ruin existing contents. If you really want the download to start from scratch, remove the file.

    Also beginning with Wget 1.7, if you use -c on a file which is of equal size as the one on the server, Wget will refuse to download the file and print an explanatory message. The same happens when the file is smaller on the server than locally (presumably because it was changed on the server since your last download attempt)---because ``continuing'' is not meaningful, no download occurs.

    On the other side of the coin, while using -c, any file that's bigger on the server than locally will be considered an incomplete download and only "(length(remote) - length(local))" bytes will be downloaded and tacked onto the end of the local file. This behavior can be desirable in certain cases---for instance, you can use wget -c to download just the new portion that's been appended to a data collection or log file.

    However, if the file is bigger on the server because it's been changed, as opposed to just appended to, you'll end up with a garbled file. Wget has no way of verifying that the local file is really a valid prefix of the remote file. You need to be especially careful of this when using -c in conjunction with -r, since every file will be considered as an ``incomplete download'' candidate.

    Another instance where you'll get a garbled file if you try to use -c is if you have a lame HTTP proxy that inserts a ``transfer interrupted'' string into the local file. In the future a ``rollback'' option may be added to deal with this case.

    Note that -c only works with FTP servers and with HTTP servers that support the "Range" header.
--progress=type
    Select the type of the progress indicator you wish to use. Legal indicators are ``dot'' and ``bar''.

    The ``bar'' indicator is used by default. It draws an ASCII progress bar graphics (a.k.a ``thermometer'' display) indicating the status of retrieval. If the output is not a TTY, the ``dot'' bar will be used by default.

    Use --progress=dot to switch to the ``dot'' display. It traces the retrieval by printing dots on the screen, each dot representing a fixed amount of downloaded data.

    When using the dotted retrieval, you may also set the style by specifying the type as dot:style. Different styles assign different meaning to one dot. With the "default" style each dot represents 1K, there are ten dots in a cluster and 50 dots in a line. The "binary" style has a more ``computer''-like orientation---8K dots, 16-dots clusters and 48 dots per line (which makes for 384K lines). The "mega" style is suitable for downloading very large files---each dot represents 64K retrieved, there are eight dots in a cluster, and 48 dots on each line (so each line contains 3M).

    Note that you can set the default style using the "progress" command in .wgetrc. That setting may be overridden from the command line. The exception is that, when the output is not a TTY, the ``dot'' progress will be favored over ``bar''. To force the bar output, use --progress=bar:force.
-N
--timestamping
    Turn on time-stamping.
-S
--server-response
    Print the headers sent by HTTP servers and responses sent by FTP servers.
--spider
    When invoked with this option, Wget will behave as a Web spider, which means that it will not download the pages, just check that they are there. You can use it to check your bookmarks, e.g. with:

            wget --spider --force-html -i bookmarks.html


    This feature needs much more work for Wget to get close to the functionality of real WWW spiders.
-T seconds
--timeout=seconds
    Set the read timeout to seconds seconds. Whenever a network read is issued, the file descriptor is checked for a timeout, which could otherwise leave a pending connection (uninterrupted read). The default timeout is 900 seconds (fifteen minutes). Setting timeout to 0 will disable checking for timeouts.

    Please do not lower the default timeout value with this option unless you know what you are doing.
--limit-rate=amount
    Limit the download speed to amount bytes per second. Amount may be expressed in bytes, kilobytes with the k suffix, or megabytes with the m suffix. For example, --limit-rate=20k will limit the retrieval rate to 20KB/s. This kind of thing is useful when, for whatever reason, you don't want Wget to consume the entire evailable bandwidth.

    Note that Wget implementeds the limiting by sleeping the appropriate amount of time after a network read that took less time than specified by the rate. Eventually this strategy causes the TCP transfer to slow down to approximately the specified rate. However, it takes some time for this balance to be achieved, so don't be surprised if limiting the rate doesn't work with very small files. Also, the ``sleeping'' strategy will misfire when an extremely small bandwidth, say less than 1.5KB/s, is specified.
-w seconds
--wait=seconds
    Wait the specified number of seconds between the retrievals. Use of this option is recommended, as it lightens the server load by making the requests less frequent. Instead of in seconds, the time can be specified in minutes using the "m" suffix, in hours using "h" suffix, or in days using "d" suffix.

    Specifying a large value for this option is useful if the network or the destination host is down, so that Wget can wait long enough to reasonably expect the network error to be fixed before the retry.
--waitretry=seconds
    If you don't want Wget to wait between every retrieval, but only between retries of failed downloads, you can use this option. Wget will use linear backoff, waiting 1 second after the first failure on a given file, then waiting 2 seconds after the second failure on that file, up to the maximum number of seconds you specify. Therefore, a value of 10 will actually make Wget wait up to (1 + 2 + ... + 10) = 55 seconds per file.

    Note that this option is turned on by default in the global wgetrc file.
--random-wait
    Some web sites may perform log analysis to identify retrieval programs such as Wget by looking for statistically significant similarities in the time between requests. This option causes the time between requests to vary between 0 and 2 * wait seconds, where wait was specified using the -w or --wait options, in order to mask Wget's presence from such analysis.

    A recent article in a publication devoted to development on a popular consumer platform provided code to perform this analysis on the fly. Its author suggested blocking at the class C address level to ensure automated retrieval programs were blocked despite changing DHCP-supplied addresses.

    The --random-wait option was inspired by this ill-advised recommendation to block many unrelated users from a web site due to the actions of one.
-Y on/off
--proxy=on/off
    Turn proxy support on or off. The proxy is on by default if the appropriate environmental variable is defined.
-Q quota
--quota=quota
    Specify download quota for automatic retrievals. The value can be specified in bytes (default), kilobytes (with k suffix), or megabytes (with m suffix).

    Note that quota will never affect downloading a single file. So if you specify wget -Q10k ftp://wuarchive.wustl.edu/ls-lR.gz, all of the ls-lR.gz will be downloaded. The same goes even when several URLs are specified on the command-line. However, quota is respected when retrieving either recursively, or from an input file. Thus you may safely type wget -Q2m -i sites---download will be aborted when the quota is exceeded.

    Setting quota to 0 or to inf unlimits the download quota.

Directory Options

-nd
--no-directories
    Do not create a hierarchy of directories when retrieving recursively. With this option turned on, all files will get saved to the current directory, without clobbering (if a name shows up more than once, the filenames will get extensions .n).
-x
--force-directories
    The opposite of -nd---create a hierarchy of directories, even if one would not have been created otherwise. E.g. wget -x http://fly.srk.fer.hr/robots.txt will save the downloaded file to fly.srk.fer.hr/robots.txt.
-nH
--no-host-directories
    Disable generation of host-prefixed directories. By default, invoking Wget with -r http://fly.srk.fer.hr/ will create a structure of directories beginning with fly.srk.fer.hr/. This option disables such behavior.
--cut-dirs=number
    Ignore number directory components. This is useful for getting a fine-grained control over the directory where recursive retrieval will be saved.

    Take, for example, the directory at ftp://ftp.xemacs.org/pub/xemacs/. If you retrieve it with -r, it will be saved locally under ftp.xemacs.org/pub/xemacs/. While the -nH option can remove the ftp.xemacs.org/ part, you are still stuck with pub/xemacs. This is where --cut-dirs comes in handy; it makes Wget not ``see'' number remote directory components. Here are several examples of how --cut-dirs option works.

            No options        -> ftp.xemacs.org/pub/xemacs/
            -nH               -> pub/xemacs/
            -nH --cut-dirs=1  -> xemacs/
            -nH --cut-dirs=2  -> .


            --cut-dirs=1      -> ftp.xemacs.org/xemacs/
            ...


    If you just want to get rid of the directory structure, this option is similar to a combination of -nd and -P. However, unlike -nd, --cut-dirs does not lose with subdirectories---for instance, with -nH --cut-dirs=1, a beta/ subdirectory will be placed to xemacs/beta, as one would expect.
-P prefix
--directory-prefix=prefix
    Set directory prefix to prefix. The directory prefix is the directory where all other files and subdirectories will be saved to, i.e. the top of the retrieval tree. The default is . (the current directory).

HTTP Options

-E
--html-extension
    If a file of type text/html is downloaded and the URL does not end with the regexp \.[Hh][Tt][Mm][Ll]?, this option will cause the suffix .html to be appended to the local filename. This is useful, for instance, when you're mirroring a remote site that uses .asp pages, but you want the mirrored pages to be viewable on your stock Apache server. Another good use for this is when you're downloading the output of CGIs. A URL like http://site.com/article.cgi?25 will be saved as article.cgi?25.html.

    Note that filenames changed in this way will be re-downloaded every time you re-mirror a site, because Wget can't tell that the local X.html file corresponds to remote URL X (since it doesn't yet know that the URL produces output of type text/html. To prevent this re-downloading, you must use -k and -K so that the original version of the file will be saved as X.orig.
--http-user=user
--http-passwd=password
    Specify the username user and password password on an HTTP server. According to the type of the challenge, Wget will encode them using either the "basic" (insecure) or the "digest" authentication scheme.

    Another way to specify username and password is in the URL itself. Either method reveals your password to anyone who bothers to run "ps". To prevent the passwords from being seen, store them in .wgetrc or .netrc, and make sure to protect those files from other users with "chmod". If the passwords are really important, do not leave them lying in those files either---edit the files and delete them after Wget has started the download.

    For more information about security issues with Wget,
-C on/off
--cache=on/off
    When set to off, disable server-side cache. In this case, Wget will send the remote server an appropriate directive (Pragma: no-cache) to get the file from the remote service, rather than returning the cached version. This is especially useful for retrieving and flushing out-of-date documents on proxy servers.

    Caching is allowed by default.
--cookies=on/off
    When set to off, disable the use of cookies. Cookies are a mechanism for maintaining server-side state. The server sends the client a cookie using the "Set-Cookie" header, and the client responds with the same cookie upon further requests. Since cookies allow the server owners to keep track of visitors and for sites to exchange this information, some consider them a breach of privacy. The default is to use cookies; however, storing cookies is not on by default.
--load-cookies file
    Load cookies from file before the first HTTP retrieval. file is a textual file in the format originally used by Netscape's cookies.txt file.

    You will typically use this option when mirroring sites that require that you be logged in to access some or all of their content. The login process typically works by the web server issuing an HTTP cookie upon receiving and verifying your credentials. The cookie is then resent by the browser when accessing that part of the site, and so proves your identity.

    Mirroring such a site requires Wget to send the same cookies your browser sends when communicating with the site. This is achieved by --load-cookies---simply point Wget to the location of the cookies.txt file, and it will send the same cookies your browser would send in the same situation. Different browsers keep textual cookie files in different locations:

        Netscape 4.x.
            The cookies are in ~/.netscape/cookies.txt.
        Mozilla and Netscape 6.x.
            Mozilla's cookie file is also named cookies.txt, located somewhere under ~/.mozilla, in the directory of your profile. The full path usually ends up looking somewhat like ~/.mozilla/default/some-weird-string/cookies.txt.
        Internet Explorer.
            You can produce a cookie file Wget can use by using the File menu, Import and Export, Export Cookies. This has been tested with Internet Explorer 5; it is not guaranteed to work with earlier versions.
        Other browsers.
            If you are using a different browser to create your cookies, --load-cookies will only work if you can locate or produce a cookie file in the Netscape format that Wget expects.

        If you cannot use --load-cookies, there might still be an alternative. If your browser supports a ``cookie manager'', you can use it to view the cookies used when accessing the site you're mirroring. Write down the name and value of the cookie, and manually instruct Wget to send those cookies, bypassing the ``official'' cookie support:

                wget --cookies=off --header "Cookie: I=I"


--save-cookies file
    Save cookies from file at the end of session. Cookies whose expiry time is not specified, or those that have already expired, are not saved.
--ignore-length
    Unfortunately, some HTTP servers (CGI programs, to be more precise) send out bogus "Content-Length" headers, which makes Wget go wild, as it thinks not all the document was retrieved. You can spot this syndrome if Wget retries getting the same document again and again, each time claiming that the (otherwise normal) connection has closed on the very same byte.

    With this option, Wget will ignore the "Content-Length" header---as if it never existed.
--header=additional-header
    Define an additional-header to be passed to the HTTP servers. Headers must contain a : preceded by one or more non-blank characters, and must not contain newlines.

    You may define more than one additional header by specifying --header more than once.

            wget --header='Accept-Charset: iso-8859-2' \
                 --header='Accept-Language: hr'        \
                   http://fly.srk.fer.hr/

    Specification of an empty string as the header value will clear all previous user-defined headers.
--proxy-user=user
--proxy-passwd=password
    Specify the username user and password password for authentication on a proxy server. Wget will encode them using the "basic" authentication scheme.

    Security considerations similar to those with --http-passwd pertain here as well.
--referer=url
    Include `Referer: url' header in HTTP request. Useful for retrieving documents with server-side processing that assume they are always being retrieved by interactive web browsers and only come out properly when Referer is set to one of the pages that point to them.
-s
--save-headers
    Save the headers sent by the HTTP server to the file, preceding the actual contents, with an empty line as the separator.
-U agent-string
--user-agent=agent-string
    Identify as agent-string to the HTTP server.

    The HTTP protocol allows the clients to identify themselves using a "User-Agent" header field. This enables distinguishing the WWW software, usually for statistical purposes or for tracing of protocol violations. Wget normally identifies as Wget/version, version being the current version number of Wget.

    However, some sites have been known to impose the policy of tailoring the output according to the "User-Agent"-supplied information. While conceptually this is not such a bad idea, it has been abused by servers denying information to clients other than "Mozilla" or Microsoft "Internet Explorer". This option allows you to change the "User-Agent" line issued by Wget. Use of this option is discouraged, unless you really know what you are doing.

FTP Options

-nr
--dont-remove-listing

Don't remove the temporary .listing files generated by FTP retrievals. Normally, these files contain the raw directory listings received from FTP servers. Not removing them can be useful for debugging purposes, or when you want to be able to easily check on the contents of remote server directories (e.g. to verify that a mirror you're running is complete).

Note that even though Wget writes to a known filename for this file, this is not a security hole in the scenario of a user making .listing a symbolic link to /etc/passwd or something and asking "root" to run Wget in his or her directory. Depending on the options used, either Wget will refuse to write to .listing, making the globbing/recursion/time-stamping operation fail, or the symbolic link will be deleted and replaced with the actual .listing file, or the listing will be written to a .listing.number file.

Even though this situation isn't a problem, though, "root" should never run Wget in a non-trusted user's directory. A user could do something as simple as linking index.html to /etc/passwd and asking "root" to run Wget with -N or -r so the file will be overwritten.
-g on/off
--glob=on/off
    Turn FTP globbing on or off. Globbing means you may use the shell-like special characters (wildcards), like *, ?, [ and ] to retrieve more than one file from the same directory at once, like:

            wget ftp://gnjilux.srk.fer.hr/*.msg

    By default, globbing will be turned on if the URL contains a globbing character. This option may be used to turn globbing on or off permanently.

    You may have to quote the URL to protect it from being expanded by your shell. Globbing makes Wget look for a directory listing, which is system-specific. This is why it currently works only with Unix FTP servers (and the ones emulating Unix "ls" output).
--passive-ftp
    Use the passive FTP retrieval scheme, in which the client initiates the data connection. This is sometimes required for FTP to work behind firewalls.
--retr-symlinks
    Usually, when retrieving FTP directories recursively and a symbolic link is encountered, the linked-to file is not downloaded. Instead, a matching symbolic link is created on the local filesystem. The pointed-to file will not be downloaded unless this recursive retrieval would have encountered it separately and downloaded it anyway.

    When --retr-symlinks is specified, however, symbolic links are traversed and the pointed-to files are retrieved. At this time, this option does not cause Wget to traverse symlinks to directories and recurse through them, but in the future it should be enhanced to do this.

    Note that when retrieving a file (not a directory) because it was specified on the commandline, rather than because it was recursed to, this option has no effect. Symbolic links are always traversed in this case.
    Recursive Retrieval Options

    -r
    --recursive
        Turn on recursive retrieving.
    -l depth
    --level=depth
        Specify recursion maximum depth level depth. The default maximum depth is 5.
    --delete-after
        This option tells Wget to delete every single file it downloads, after having done so. It is useful for pre-fetching popular pages through a proxy, e.g.:

                wget -r -nd --delete-after http://whatever.com/~popular/page/


        The -r option is to retrieve recursively, and -nd to not create directories.

        Note that --delete-after deletes files on the local machine. It does not issue the DELE command to remote FTP sites, for instance. Also note that when --delete-after is specified, --convert-links is ignored, so .orig files are simply not created in the first place.
    -k
    --convert-links
        After the download is complete, convert the links in the document to make them suitable for local viewing. This affects not only the visible hyperlinks, but any part of the document that links to external content, such as embedded images, links to style sheets, hyperlinks to non-HTML content, etc.

        Each link will be changed in one of the two ways:

            *
                The links to files that have been downloaded by Wget will be changed to refer to the file they point to as a relative link.

                Example: if the downloaded file /foo/doc.html links to /bar/img.gif, also downloaded, then the link in doc.html will be modified to point to ../bar/img.gif. This kind of transformation works reliably for arbitrary combinations of directories.
            *
                The links to files that have not been downloaded by Wget will be changed to include host name and absolute path of the location they point to.

                Example: if the downloaded file /foo/doc.html links to /bar/img.gif (or to ../bar/img.gif), then the link in doc.html will be modified to point to http://hostname/bar/img.gif.

            Because of this, local browsing works reliably: if a linked file was downloaded, the link will refer to its local name; if it was not downloaded, the link will refer to its full Internet address rather than presenting a broken link. The fact that the former links are converted to relative links ensures that you can move the downloaded hierarchy to another directory.

            Note that only at the end of the download can Wget know which links have been downloaded. Because of that, the work done by -k will be performed at the end of all the downloads.

    -K
    --backup-converted
        When converting a file, back up the original version with a .orig suffix. Affects the behavior of -N.
    -m
    --mirror
        Turn on options suitable for mirroring. This option turns on recursion and time-stamping, sets infinite recursion depth and keeps FTP directory listings. It is currently equivalent to -r -N -l inf -nr.
    -p
    --page-requisites
        This option causes Wget to download all the files that are necessary to properly display a given HTML page. This includes such things as inlined images, sounds, and referenced stylesheets.

        Ordinarily, when downloading a single HTML page, any requisite documents that may be needed to display it properly are not downloaded. Using -r together with -l can help, but since Wget does not ordinarily distinguish between external and inlined documents, one is generally left with ``leaf documents'' that are missing their requisites.

        For instance, say document 1.html contains an "< IMG >" tag referencing 1.gif and an "< A >" tag pointing to external document 2.html. Say that 2.html is similar but that its image is 2.gif and it links to 3.html. Say this continues up to some arbitrarily high number.

        If one executes the command:

                wget -r -l 2 http://I/1.html


        then 1.html, 1.gif, 2.html, 2.gif, and 3.html will be downloaded. As you can see, 3.html is without its requisite 3.gif because Wget is simply counting the number of hops (up to 2) away from 1.html in order to determine where to stop the recursion. However, with this command:

                wget -r -l 2 -p http://I/1.html


        all the above files and 3.html's requisite 3.gif will be downloaded. Similarly,

                wget -r -l 1 -p http://I/1.html


        will cause 1.html, 1.gif, 2.html, and 2.gif to be downloaded. One might think that:

                wget -r -l 0 -p http://I/1.html


        would download just 1.html and 1.gif, but unfortunately this is not the case, because -l 0 is equivalent to -l inf---that is, infinite recursion. To download a single HTML page (or a handful of them, all specified on the commandline or in a -i URL input file) and its (or their) requisites, simply leave off -r and -l:

                wget -p http://I/1.html


        Note that Wget will behave as if -r had been specified, but only that single page and its requisites will be downloaded. Links from that page to external documents will not be followed. Actually, to download a single page and all its requisites (even if they exist on separate websites), and make sure the lot displays properly locally, this author likes to use a few options in addition to -p:

                wget -E -H -k -K -p http://I/I

        To finish off this topic, it's worth knowing that Wget's idea of an external document link is any URL specified in an "< A >" tag, an "" tag, or a "" tag other than "".

    Recursive Accept/Reject Options

    -A acclist --accept acclist
    -R rejlist --reject rejlist
        Specify comma-separated lists of file name suffixes or patterns to accept or reject.
    -D domain-list
    --domains=domain-list
        Set domains to be followed. domain-list is a comma-separated list of domains. Note that it does not turn on -H.
    --exclude-domains domain-list
        Specify the domains that are not to be followed..
    --follow-ftp
        Follow FTP links from HTML documents. Without this option, Wget will ignore all the FTP links.
    --follow-tags=list
        Wget has an internal table of HTML tag / attribute pairs that it considers when looking for linked documents during a recursive retrieval. If a user wants only a subset of those tags to be considered, however, he or she should be specify such tags in a comma-separated list with this option.
    -G list
    --ignore-tags=list
        This is the opposite of the --follow-tags option. To skip certain HTML tags when recursively looking for documents to download, specify them in a comma-separated list.

        In the past, the -G option was the best bet for downloading a single page and its requisites, using a commandline like:

                wget -Ga,area -H -k -K -r http://I/I

        However, the author of this option came across a page with tags like "" and came to the realization that -G was not enough. One can't just tell Wget to ignore "", because then stylesheets will not be downloaded. Now the best bet for downloading a single page and its requisites is the dedicated --page-requisites option.
    -H
    --span-hosts
        Enable spanning across hosts when doing recursive retrieving.
    -L
    --relative
        Follow relative links only. Useful for retrieving a specific home page without any distractions, not even those from the same hosts.
    -I list
    --include-directories=list
        Specify a comma-separated list of directories you wish to follow when downloading Elements of list may contain wildcards.
    -X list
    --exclude-directories=list
        Specify a comma-separated list of directories you wish to exclude from download Elements of list may contain wildcards.
    -np
    --no-parent
        Do not ever ascend to the parent directory when retrieving recursively. This is a useful option, since it guarantees that only the files below a certain hierarchy will be downloaded.

    EXAMPLES
    The examples are divided into three sections loosely based on their complexity.
    Simple Usage

    *
        Say you want to download a URL. Just type:

                wget http://fly.srk.fer.hr/

    *
        But what will happen if the connection is slow, and the file is lengthy? The connection will probably fail before the whole file is retrieved, more than once. In this case, Wget will try getting the file until it either gets the whole of it, or exceeds the default number of retries (this being 20). It is easy to change the number of tries to 45, to insure that the whole file will arrive safely:

                wget --tries=45 http://fly.srk.fer.hr/jpg/flyweb.jpg

    *
        Now let's leave Wget to work in the background, and write its progress to log file log. It is tiring to type --tries, so we shall use -t.

                wget -t 45 -o log http://fly.srk.fer.hr/jpg/flyweb.jpg &

        The ampersand at the end of the line makes sure that Wget works in the background. To unlimit the number of retries, use -t inf.
    *
        The usage of FTP is as simple. Wget will take care of login and password.

                wget ftp://gnjilux.srk.fer.hr/welcome.msg

    *
        If you specify a directory, Wget will retrieve the directory listing, parse it and convert it to HTML. Try:

                wget ftp://prep.ai.mit.edu/pub/gnu/
                links index.html


    Advanced Usage

    *
        You have a file that contains the URLs you want to download? Use the -i switch:

                wget -i I

        If you specify - as file name, the URLs will be read from standard input.
    *
        Create a five levels deep mirror image of the GNU web site, with the same directory structure the original has, with only one try per document, saving the log of the activities to gnulog:

                wget -r http://www.gnu.org/ -o gnulog


    *
        The same as the above, but convert the links in the HTML files to point to local files, so you can view the documents off-line:

                wget --convert-links -r http://www.gnu.org/ -o gnulog


    *
        Retrieve only one HTML page, but make sure that all the elements needed for the page to be displayed, such as inline images and external style sheets, are also downloaded. Also make sure the downloaded page references the downloaded links.

                wget -p --convert-links http://www.server.com/dir/page.html


        The HTML page will be saved to www.server.com/dir/page.html, and the images, stylesheets, etc., somewhere under www.server.com/, depending on where they were on the remote server.
    *
        The same as the above, but without the www.server.com/ directory. In fact, I don't want to have all those random server directories anyway---just save all those files under a download/ subdirectory of the current directory.

                wget -p --convert-links -nH -nd -Pdownload \
                     http://www.server.com/dir/page.html

    *
        Retrieve the index.html of www.lycos.com, showing the original server headers:

                wget -S http://www.lycos.com/

    *
        Save the server headers with the file, perhaps for post-processing.

                wget -s http://www.lycos.com/
                more index.html


    *
        Retrieve the first two levels of wuarchive.wustl.edu, saving them to /tmp.

                wget -r -l2 -P/tmp ftp://wuarchive.wustl.edu/

    *
        You want to download all the GIFs from a directory on an HTTP server. You tried wget http://www.server.com/dir/*.gif, but that didn't work because HTTP retrieval does not support globbing. In that case, use:

                wget -r -l1 --no-parent -A.gif http://www.server.com/dir/

        More verbose, but the effect is the same. -r -l1 means to retrieve recursively, with maximum depth of 1. --no-parent means that references to the parent directory are ignored, and -A.gif means to download only the GIF files. -A ``*.gif'' would have worked too.
    *
        Suppose you were in the middle of downloading, when Wget was interrupted. Now you do not want to clobber the files already present. It would be:

                wget -nc -r http://www.gnu.org/

    *
        If you want to encode your own username and password to HTTP or FTP, use the appropriate URL syntax.

                wget ftp://hniksic:mypassword@unix.server.com/.emacs

        Note, however, that this usage is not advisable on multi-user systems because it reveals your password to anyone who looks at the output of "ps".
    *
        You would like the output documents to go to standard output instead of to files?

                wget -O - http://jagor.srce.hr/ http://www.srce.hr/

        You can also combine the two options and make pipelines to retrieve the documents from remote hotlists:

                wget -O - http://cool.list.com/ | wget --force-html -i -


    Very Advanced Usage

    *
        If you wish Wget to keep a mirror of a page (or FTP subdirectories), use --mirror (-m), which is the shorthand for -r -l inf -N. You can put Wget in the crontab file asking it to recheck a site each Sunday:

                crontab
                0 0 * * 0 wget --mirror http://www.gnu.org/ -o /home/me/weeklog


    *
        In addition to the above, you want the links to be converted for local viewing. But, after having read this manual, you know that link conversion doesn't play well with timestamping, so you also want Wget to back up the original HTML files before the conversion. Wget invocation would look like this:

                wget --mirror --convert-links --backup-converted  \
                     http://www.gnu.org/ -o /home/me/weeklog


    *
        But you've also noticed that local viewing doesn't work all that well when HTML files are saved under extensions other than .html, perhaps because they were served as index.cgi. So you'd like Wget to rename all the files served with content-type text/html to name.html.

                wget --mirror --convert-links --backup-converted \
                     --html-extension -o /home/me/weeklog        \
                     http://www.gnu.org/

        Or, with less typing:

                wget -m -k -K -E http://www.gnu.org/ -o /home/me/weeklog

large zip split into small files on linux (ubuntu 12.10 and older version)

The way to spit large zip files into small zip files on linux (ubuntu 12.10 and older version)
cd /home/vina/Desktop/ieeezip (change the file path to where you want to keep the split files)
to split

tar -cvj /home/vina/LTEieee.zip | split -b 5m -d – “LTEieee.tar.bz.”

m denotes MB
to get back
cat large-files.tar.bz.* > large-files.tar.bz
tar -xvj large-file.tar.bz

How to View .Chm files in Linux

Chm files are Microsoft help files. They can be viewed or opened in linux using Gnochm, Kchm, Kchmviewer and Xchm.

Gnochm is used in Gnome desktop environment (you can use this in KDE but its recommended to use Kchm or kchmviewer). Kchm and Kchmviewer are KDE desktop applications and they can be used to view .CHM Files in KDE. Xchm is a xwindow application with minimal graphical interface. It looks outdated but works fine.

to open a file you have to type it like

    $xchm filename.chm



Data packets conversions in seconds
1000 bps = 125 B/s
1 byte= 8 bits
kbit/s=10^3
Kibits/s = 2^10 = 1024
megabit = 1,000,000
Megibit = 1,048,576
k -kilo - 1000
ki- kilobinary -1024
KiB-1024^1
kB = 1000^1
MB = 1000^2
GB = 1000^3
TB = 1000^4
PB = 1000^5


The location for MatLab application on Linux (ubuntu 12.10 and older versions)
Use the command in the open terminal to run matlab application
CTRL+ALT+T
/usr/local/MATLAB/R2012a/bin/
./matlab


How to compile and run the progam in C,C++ code on linux terminal
The gcc command compiles a C program, and g++ compiles a C++ program

You can compile a C program (written using a text editor such as vi) by using the gcc command. For example, if the name of your program file is "assignment1.c", to compile it you may type in the following:

vina>gcc assignment1.c

OR
To compile a C++ program called "assignment1.cpp":

vina>g++ assignment1.cpp

At this point if there are errors in your program the compiler will show them on the screen and then return you to the prompt. You should then correct these errors by opening the program in your text editor.

After you have corrected your errors, you may use the same gcc or g++ command to compile it again. If there are no errors in your code the compiler will return you to the prompt without any error messages. This means that your code has been compiled into a separate executable file which by default is named as a.out. You may run the code by typing in a.out at the prompt as follows:

vina>a.out

If you wish to give a specific name to your compiled program (suppose you want to call it "assignment1") you may do this using one of the following commands instead of the regular gcc or g++ command:

For a C program:
vina>gcc -o assignment1 assignment1.c

OR
For a C++ program:
vina>gcc -o assignment1 assignment1.c

You program will be compiled into a executable file called "assignment1". As in the case of "a.out" you may run this by simply typing in "assignment1" at the prompt as follows.

vina>assignment1

Tuesday, July 31, 2012

How to rar/unrar the files on Linux operating system using open command terminal

Using rarlinux
download rarlinux tool from win-rar website and Gunzip the downloaded rarlinux-3.7.1.tar.gzip file
[root@vinsun]#gunzip rarlinux-3.7.1.tar.gzip
To extract the gunzipped but .tar file
[root@vinsun]#tar xvf rarlinux-3.7.1.tar
The above will extract the tar file to a folder in your present working directory called rar.
enter tho the rar dir
[root@vinsun]# cd ./rar
long list the rar folder -
[root@vinsun]# ls -l ./rar
You should see an executable file called unrar. There you go -
To unrar a file -
[root@vinsun]# ./unrar x file.rar
To extract a password protected rar file -
[root@vinsun]#./unrar x -p[password] file.rar


Using unrar:
Fetch and install unrar tools from fedora extra repository -
[root@cafe moon]#yum install unrar
To see unrar help pages-
[root@cafe moon]# unrar ?
To extract a rar file -
[root@cafe moon]# unrar x file.rar
To extract a password protected rar file -
[root@cafe moon]#unrar x -p[password] file.rar

Using rarlinux:
Download the rarlinux tool from Winrar website and Gunzip the downloaded rarlinux-3.7.1.tar.gzip file
[root@cafe moon]#gunzip rarlinux-3.7.1.tar.gzip
To extract the gunzipped but .tar file
[root@cafe moon]#tar xvf rarlinux-3.7.1.tar
The above will extract the tar file to a folder in your present working directory called rar.
enter tho the rar dir
[root@cafe moon]# cd ./rar
long list the rar folder -
[root@cafe moon]# ls -l ./rar
You should see an executable file called unrar. There you go -
To unrar a file -
[root@cafe moon]# ./unrar x file.rar
To extract a password protected rar file -
[root@cafe moon]#./unrar x -p[password] file.rar