CS 497C

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CS 497C Introduction to UNIXLecture 7
General-Purpose Utilities

• Chin-Chih Changchang_at_cs.twsu.edu

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script Record Your Session

• If you want to keep track of all your activities,
  you can invoke the script command after you log
  in
• script
• Script started, file is typescript
• All your keystrokes that you enter get recorded
  in the file typescript.

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script Record Your Session

• You can view this file with the cat command.
• Script overwrites any previous typescript file.
• To append activities to existing file typescript,
  use
• script -a
• To log activities to a different log file, use
• script logfile

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clear and tput Clear Your Screen

• There are two commands available in most UNIX
  systems to clear your screen clear and tput.
• The clear command is used without arguments
• clear
• The tput command is used with the clear argument
• tput clear

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clear and tput Clear Your Screen

• tput can als position the cursor at a specific
  location or be used to highlight text.
• tput cup 10 20
• You can boldface your text by using the smso and
  rmso arguments. smso starts highlighting the text
  and rmso ends highlighting.
• tput smso
• echo Come to the Web
• tput rmso

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uname Know Your Machines Name

• If your machine is connected to the Internet,
  then your machine name forms part of your
  machines domain name (a series of words
  separated by dots).
• Use n option to show the machine name in a
  network
• uname n
• sisko
• Use r option to show the operating systems
  version.

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date Display The System Date

• The UNIX system maintains an internal clock meant
  to run perpetually. When the system is shut down,
  a battery backup keeps the clock ticking.
• The clock actually stores the number of seconds
  elapsed since January 1, 1970.
• You can display the current date with the date
  command.

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date Display The System Date

• The date command can display specific format by a
  symbol followed by the operator and a single
  character describing the format
• d the day of the month (1 to 31)
• m month in the number format (1 to 12)
• h month name
• y the last two digits of the year
• H, M, and S the hour, minute and second,
  respectively.

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date Display The System Date

• You can combine them in the format where the
  symbol precedes a string which specifies the
  requested format within a pair of symbols.
• To show the month name, date, and, you can use
  the following command
• date h d y
• Sep 3 01
• To change the system date, you need the
  administrator permission.

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cal The Calender

• cal is a handy tool that you can invoke anytime
  to see the calendar of any specific month or a
  complete year.
• To show December, use
• cal dec
• To show the year of 2002, use
• cal 2002 more
• The symbol connects two commands (in a
  pipeline) where more takes input from the cal
  command.

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calendar A useful Reminder Mechanism

• The calendar command provides a useful reminder
  mechanism for a user. The command searches a file
  named calendar in the current directory
• cat calendar
• Sep 3 Labor Day
• Sep 5 Howework Due

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calendar A useful Reminder Mechanism

• You can use date and calendar in a sequence to
  show those lines containing todays and
  tomorrows dates.
• date
• Mon Sep 3 123014 CDT 2001
• calendar
• Sep 3 Labor Day

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bc The Calculator

• Two types of calculators are available in UNIX
  a graphical object (the xcalc command) and the
  character-based bc command.
• bc belongs to a family of commands (called
  filters) that expect input from the keyboard when
  used without any argument.
• Key in the following arithmetic expression
• bc
• 12 5
• 17

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bc The Calculator

• bc added the two numbers and showed the output in
  the next time.
• To quit bc, you have to use Ctrl-d that marks
  the end of input.
• You can also ask bc to perform calculations
  together
• 1212 232
• 144
• 4294967296

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bc The Calculator

• By default, bc performs truncated division, and
  you have to set scale to the number of digits of
  precision before you perform any division
• 9/5
• 1
• scale 2
• 17/7
• 2.42

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bc The Calculator

• bc is quite useful in converting numbers from one
  base to another.
• An example to convert a binary number to a
  decimal one is shown as follows
• ibase2
• 11001010
• 202

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bc The Calculator

• The reverse is possible
• obase 2
• 14
• 1110
• You can convert from one base to the another
• obase 16
• 14
• E

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bc The Calculator

• bc can be used with variables
• x 3 y 4 z 5
• p x y z
• p
• 12
• bc is a pseudo-programming language featuring
  arrays, functions, conditionals (if) and loops
  (for and while). It also comes with a library for
  performing scientific calculations.

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More General Purpose Commands

• Copy, rename and delete files with cp, mv and rm.
• View and print a file with cat, more, and lp.
• Compress a file with compress and gzip.
• Find out disk space utilization with df and du.

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More General Purpose Commands

• Extract the two ends of a file with head and
  tail.
• Cut and past a file with cut and paste.
• Find differences between two files with comm,
  cmp, and diff.
• Sort a files contents with sort.