Perl Interview Questions and Answers Collection

linux: date

date  

date can be used by a lot of applications in various forms. you may require to access a month,day, hour or second of  a particular date.

You may use the following options to achieve these functionalities.

%%   a literal %

 %a   locale's abbreviated weekday name (Sun..Sat)

 %A   locale's full weekday name, variable length (Sunday..Saturday)

 %b   locale's abbreviated month name (Jan..Dec)

 %B   locale's full month name, variable length (January..December)

 %c   locale's date and time (Sat Nov 04 12:02:33 EST 1989)

 %d   day of month (01..31)

 %D   date (mm/dd/yy)

 %e   day of month, blank padded ( 1..31)

 %h   same as %b

 %H   hour (00..23)

 %I   hour (01..12)

 %j   day of year (001..366)

 %k   hour ( 0..23)

 %l   hour ( 1..12)

 %m   month (01..12)

 %M   minute (00..59)

 %n   a newline

 %p   locale's AM or PM

 %r   time, 12-hour (hh:mm:ss [AP]M)

 %s   seconds since 00:00:00, Jan 1, 1970 (a GNU extension)

 %S   second (00..60)

 %t   a horizontal tab

 %T   time, 24-hour (hh:mm:ss)

 %U   week number of year with Sunday as first day of week (00..53)

 %V   week number of year with Monday as first day of week (01..52)

 %w   day of week (0..6);  0 represents Sunday

 %W   week number of year with Monday as first day of week (00..53)

 %x   locale's date representation (mm/dd/yy)

 %X   locale's time representation (%H:%M:%S)

 %y   last two digits of year (00..99)

 %Y   year (1970...)

 %z   RFC-822 style numeric timezone (-0500) (a nonstandard extension)

 %Z   time zone (e.g., EDT), or nothing if no time zone is determinable

To get the the current  month,year and day in mmddyyyy  format ,enter

date + ‘ %m%d%Y’

Crontab Commands

Crontab Commands

export EDITOR=vi ;to specify a editor to open crontab file.

crontab -e    Edit your crontab file, or create one if it doesn’t already exist.
crontab -l      Display your crontab file.
crontab -r      Remove your crontab file.
crontab -v      Display the last time you edited your crontab file. (This option is only available on a few systems.)

Shell Function in Vi editor

Shell Functions

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:! cmd	Executes shell command cmd; you can add these special characters to indicate:% name of current file# name of last file edited
!! cmd	Executes shell command cmd, places output in file starting at current line
:!!	Executes last shell command
:r! cmd	Reads and inserts output from cmd
:f file	Renames current file to file
:w !cmd	Sends currently edited file to cmd as standard input and execute cmd
:cd dir	Changes current working directory to dir
:sh	Starts a sub-shell (CTRL-d returns to editor)
:so file	Reads and executes commands in file (file is a shell script)
!Motion_cmd	Sends text from current position to Motion Command to shell command cmd
!}sort	Sorts from current position to end of paragraph and replaces text with sorted text