How to Output Leading Zeros in Ruby

How can I output leading zeros in Ruby?

If the maximum number of digits in the counter is known (e.g., n = 3 for counters 1..876), you can do

str = "file_" + i.to_s.rjust(n, "0")

How to work with leading zeros in integers

A numeric literal that starts with 0 is an octal representation, except the literals that start with 0x which represent hexadecimal numbers or 0b which represent binary numbers.

1 * 8**2 + 1 * 8**1 + 2 * 8**0 == 74

To convert it to 0112, use String#% or Kernel#sprintf with an appropriate format string:

'0%o' % 0112  # 0: leading zero, %o: represent as an octal
# => "0112"

Leading zeros in Ruby

It'd be better to store it as an integer and just display it as you described on runtime. Every language has its own way to pad zeros - for Ruby you can use String#rjust. This method pads a string (right-justified) so that it becomes a given length, using a given padding character.

str.rjust(integer, padstr=' ') → new_str

If integer is greater than the length of str, returns a new String of length integer with str right justified and padded with padstr; otherwise, returns str.

some_int = 5
some_int.to_s.rjust(2, '0')  # => '05'
some_int.to_s.rjust(5, '0')  # => '00005'

another_int = 150
another_int.to_s.rjust(2, '0') # => '150'
another_int.to_s.rjust(3, '0') # => '150'
another_int.to_s.rjust(5, '0') # => '00150'

Padding a number with zeros

puts 1.to_s.rjust(3, "0")
#=> 001
puts 10.to_s.rjust(3, "0")
#=> 010
puts 100.to_s.rjust(3, "0")
#=> 100

The above code would convert your user.id into a string, then String.rjust() method would consider its length and prefix appropriate number of zeros.

How do I insert leading zeros in Ruby dateTime minute

try

system["last_checkin"].to_time.strftime('%H:%M')

which will convert it to a Time(which has the date) and then you can use strftime to get the format you want

Ruby on Rails: How do you add add zeros in front of a number if it's under 10?

Did you mean sprintf '%02d', n?

irb(main):003:0> sprintf '%02d', 1
=> "01"
irb(main):004:0> sprintf '%02d', 10
=> "10"

You might want to reference the format table for sprintf in the future, but for this particular example '%02d' means to print an integer (d) taking up at least 2 characters (2) and left-padding with zeros instead of spaces (0).

Retain 0's when incrementing number

You can convert an integer to a String and give it a fixed amount of padding using String#rjust, where the first argument is the total width of the resulting String, and the second argument is the character to use for padding:

>> int = 3
>> str = int.to_s.rjust(3, '0')
#=> "003"

And then you can increment that string using String#next:

>> str.next
#=> "004"

Ruby: leading zeros with already formatted string

Because it was interpreted as an octal number.

Try it in irb:

> 0301
=> 193

But when you write:

> 301
=> 301

If you want to make it work, try to convert it to integer with String#to_i:

"%06d" % s.to_i
sprintf("%06d", s.to_i)

Format a ruby decimal to string without leading zero (.123)

Solution

You can use :

format('%.3f', value).sub(/^0/, '')

It removes the first character if it is a 0 followed by a dot.

Test

values = [
  0.725,
  1.5,
  0.125,
  2.4567,
  0,
  10
]

values.each do |value|
  p format('%.3f', value).sub(/^0/, '')
end

#=>
# ".725"
# "1.500"
# ".125"
# "2.457"
# ".000"
# "10.000"

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