General Purpose Utilities

Calendar

The cal command to see the calculator of any specific month or a complete year.

Syntax:    cal [[ month ] year ]

ex: cal  03 2016

cal 2016 | more

ECHO:

echo is one of the most commonly and widely used built-in command for Linux bash and C shells, that typically used in scripting language and batch files to display a line of text/string on standard output or a file.

Syntax:  echo [OPTION]... [STRING]...

Example: echo "hello"  output: helloSyntax: 

ex: echo -e "Tecmint \bis \ba \bcommunity \bof \bLinux \bNerds" 

TecmintisacommunityofLinuxNerds 

echo -e "Tecmint \nis \na \ncommunity \nof \nLinux \nNerds" 

Tecmint 

is 

a 

community 

of 

Linux 

Nerds uxNerds 

Echo the STRING(s) to standard output.

Tag	Description
-n	do not output the trailing newline
-e	enable interpretation of backslash escapes
-E	disable interpretation of backslash escapes (default)
--help	display this help and exit
--version
	output version information and exit
If -e is in effect, the following sequences are recognized:
\0NNN	the character whose ASCII code is NNN (octal)
\\	backslash
\a	alert (BEL)
\b	backspace
\c	suppress trailing newline
\f	form feed
\n	new line
\r	carriage return
\t	horizontal tab
\v	vertical tab

Printf:

Display text in formatted 

%s   String

%30s     print space in a 30 characters wide

%d    decimal

%o  octal

%x Hexadecimal

%f  Floating point number

Example 

$ printf "%s\n" "hello printf" "in" "bash script"

hello printf

in

bash script

bc - Unix calculator

bc is a unix command which stands for bench calcultor. Depending on the way we use it, it can either look like a programming language or as a interactive mathematic shell. Let us see in this article how to use bc  to do some simple arithmetic.

bc

bc 1.06

Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.

This is free software with ABSOLUTELY NO WARRANTY.

For details type `warranty'.

100+500

600

1000/3

333

passwd ---- Assigning password

passwd username

who are the users

w ---- to know who are the users connected

who am i

Uname: features of operating system.

uname -a  ----- all the details

uname -r ----    kernel version

DATE : Displaying the System Date

you can display the current date with date command, which shows the date and time to nearest second.

Syntax: date

 date
Fri Jan 22 17:39:08 IST 2016

Format:

 date '+DATE: %m/%d/%y%nTIME:%H:%M:%S'

output:

DATE: 01/22/16

TIME:17:54:15

DESCRIPTION

Display the current time in the given FORMAT, or set the system date.

-d, --date=STRING       display time described by STRING, not `now'

-f, --file=DATEFILE  like --date once for each line of DATEFILE

-r, --reference=FILE  display the last modification time of FILE

-R, --rfc-2822  output date and time in RFC 2822 format. Example: Mon, 07 Aug 2006 12:34:56 -0600

--rfc-3339=TIMESPEC output date and time in RFC 3339 format. TIMESPEC=`date', `seconds', or `ns' for date and time to the indicated precision. Date and time components are separated by a single space: 2006-08-07 12:34:56-06:00

-s, --set=STRING set time described by STRING

-u, --utc, --universal print or set Coordinated Universal Time

--help display this help and exit

--version output version information and exit

FORMAT controls the output. Interpreted sequences are: 

%%  a literal %

%a  locale's abbreviated weekday name (e.g., Sun)

%A  locale's full weekday name (e.g., Sunday)

%b  locale's abbreviated month name (e.g., Jan)

%B  locale's full month name (e.g., January)

%c locale's date and time (e.g., Thu Mar 3 23:05:25 2005)

%C  century; like %Y, except omit last two digits (e.g., 20)

%d day of month (e.g., 01)

%D date; same as %m/%d/%y

%e day of month, space padded; same as %_d

%F full date; same as %Y-%m-%d

%g last two digits of year of ISO week number (see %G)

%G year of ISO week number (see %V); normally useful only with %V

%h same as %b

%H hour (00..23)

%I hour (01..12)

%j day of year (001..366)

%k hour, space padded ( 0..23); same as %_H

%l hour, space padded ( 1..12); same as %_I

%m month (01..12)

%M minute (00..59)

%n a newline

%N nanoseconds (000000000..999999999)

%p locale's equivalent of either AM or PM; blank if not known

%P like %p, but lower case

%r locale's 12-hour clock time (e.g., 11:11:04 PM)

%R 24-hour hour and minute; same as %H:%M

%s seconds since 1970-01-01 00:00:00 UTC

%S second (00..60)

%t a tab

%T time; same as %H:%M:%S

%u day of week (1..7); 1 is Monday

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

%V ISO week number, with Monday as first day of week (01..53)

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

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

%x locale's date representation (e.g., 12/31/99)

%X locale's time representation (e.g., 23:13:48)

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

%Y year

%z +hhmm numeric time zone (e.g., -0400)

%:z +hh:mm numeric time zone (e.g., -04:00)

%::z  +hh:mm:ss numeric time zone (e.g., -04:00:00)

%:::z numeric time zone with : to necessary precision (e.g., -04, +05:30)

%Z alphabetic time zone abbreviation (e.g., EDT)

By default, date pads numeric fields with zeroes. The following optional flags may follow `%':

- (hyphen) do not pad the field

_ (underscore) pad with spaces

0 (zero) pad with zeros

^ use upper case if possible

# use opposite case if possible

Examples:

date +%m   ---- display month in numeric

date +"%h %m"

[root@rhel6 ~]# date +%a

Sat

[root@rhel6 ~]# date +%A

Saturday

[rootrhel6 ~]# date +%M

31

[root@rhel6 ~]# date +%m

12

[root@rhel6 ~]# date +%a

Sat

[root@rhel6 ~]# date +%A

Saturday

[root@rhel6 ~]# date +%B

December

[root@rhel6 ~]# date +%b

Dec

[root@rhel6 ~]# date

Sat Dec 19 00:32:14 IST 2015

[root@rhel6 ~]#

d ----- the day of the month ( 1-31)

y ----- the last two digits

H,M and S   hour , min and sec

D ---- The date in format dd/mm/yy

T ----- Time  hh:mm:ss