Golang: Pad right or print ending(suffix) zero or spaces in fmt.Printf example



Tags : golang pad-right ending-zero fmt-printf suffix

From the previous tutorial on how to pad left or print leading zeros with fmt.Printf() function, a reader asked how to pad zeros on right side or print ending zeros to a number.

From https://golang.org/pkg/fmt/ - Other flags:

We can see that there is an option to do just that.... for spaces

- pad with spaces on the right rather than the left (left-justify the field)

Therefore, to pad right or print ending space, all you need to do is to add the - sign.

However, the trouble is that many people are confused why the - flag does not pad zero at the right side. If you read between the line, the - is working as advertise because it only pads spaces, nothing else. To pad zero(or any other character) to right side, we will need to create our function to do that. See code example below.

Here we go!

 package main

 import (
 "fmt"
 "strings"
 )

 func padRightSide(str string, item string, count int) string {
 return str + strings.Repeat(item, count)
 }

 func main() {
 // you want to display 000108 (length = 6)
 // pad zero to total length of 6
 // d
 fmt.Printf("Leading or pad left with zero :  |d|\n", 108)

 // pad spaces in front(prefix)
 fmt.Printf("Leading or pad left with space : |%6d|\n", 108)

 // the flag - here WILL NOT work because it only move spaces to the right
 // YES only spaces, nothing else...not even zero
 fmt.Printf("Ending or pad RIGHT with zero(will NOT work) :  |%-06d|\n", 108)

 // to pad zero or anything else, we will use the padRightSide function
 fmt.Printf("Ending or pad RIGHT with zero :  |%v|\n", padRightSide("108", "0", 3))

 // pad spaces at end(suffix)
 // this will work.
 fmt.Printf("Ending or pad RIGHT with space : |%-6d|\n", 108)

 }

Output:

Leading or pad left with zero : |000108|

Leading or pad left with space : | 108|

Ending or pad RIGHT with zero(will NOT work) : |108 |

Ending or pad RIGHT with zero : |108000|

Ending or pad RIGHT with space : |108 |

Hope this helps!

References:

https://golang.org/pkg/fmt/

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Tags : golang pad-right ending-zero fmt-printf suffix

By Adam Ng

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