Add zero-padding to a string

How do I add "0" padding to a string so that my string length is always 4?

Example

If input "1", 3 padding is added = 0001
If input "25", 2 padding is added = 0025
If input "301", 1 padding is ad开发者_开发知识库ded = 0301
If input "4501", 0 padding is added = 4501

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You can use PadLeft

var newString = Your_String.PadLeft(4, '0');

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myInt.ToString("D4");

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string strvalue="11".PadRight(4, '0');

output= 1100

string strvalue="301".PadRight(4, '0');

output= 3010

string strvalue="11".PadLeft(4, '0');

output= 0011

string strvalue="301".PadLeft(4, '0');

output= 0301

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"1".PadLeft(4, '0');

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int num = 1;
num.ToString("0000");

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with sed

• always add three leading zeroes
• then trim to 4 digits

sed -e 's/^/000/;s/^0*\([0-9]\{4,\}\)$/\1/'