Saturday, November 5, 2011

The date utility-Part 1

date utility is used to display current time and date.No user can modify the date and time unless they are the  superuser  i.e the system administrator.This is required for the smooth functioning of the system. 
              date[-a[-]sss.fff][-u][[mmdd]HHMM | mmddHHMM[cc]yy]
 If no argument is given, or if the argument begins with +, the current  current date and time are printed.

-a[-]sss.fff     Slowly adjusts the time by sss.fff seconds,where fff represents fractions of a          
                        second.The adjustment can be positive or negative.The clock of the system will be
                        speeded up or slowed until it has drifted by the number of seconds specified.
-u                    Displays (or sets) the date in GMT(Greenwich Mean Time), bypassing the normal 
                        conversion to or from normal or local time.
mm                 is the month 
dd                   is the day of the month
HH                  is the hour in the 24 hr system.
MM                 is the minute 
cc                   is the century minus one.
yy                   is the last two digits of the year .The month, day,year and century may be
                        omitted; the current values are applied as defaults. 
                        For eg: date 12301600 sets the date to Dec 30, 4:00 PM. The current year is the  
                        default because no year is supplied . The system operates in GMT. date takes  
                        care of the conversion to and from the local standard and daylight saving time.
                        Only the superuser may change the date.After successfully setting the date and  
                        time date displays the new date according to the default format. The date utility
                        uses the TZ in environ  command to determine the correct time zone information.
+format         If the argument begins with +, the output of the date is under the control of the  
                        user. Each Field Descriptor, described in the next post,is preceeded by %, and  
                        is replaced  in the output by its corresponding value.A single % is encoded by  
                        %%.  All other characters are copied to the output without change. The string is 
                        always  terminated by a newline character.If the argument contains embedded 
                        blanks ,it must be qouted. 

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