How can I output leading zeros in Ruby

Question

I m outputting a set of numbered files from a Ruby script  The numbers come from incrementing a counter  but to make them sort nicely in the directory  I d like to use leading zeros in the filenames  In other words     file 001      instead of     file 1   Is there a simple way to add leading zeros when converting a number to a string   I know I can do  if less than 10     if less than 100

User · Answer

As stated by the other answers    03d    number works pretty well  but it goes against the rubocop ruby style guide      Favor the use of sprintf and its alias format over the fairly    cryptic String   method   We can obtain the same result in a more readable way using the following   format   03d   number

User · Answer

Use the   operator with a string   irb main  001 0 gt    03d    5   gt   005    The left-hand-side is a printf format string  and the right-hand side can be a list of values  so you could do something like   irb main  002 0 gt  filename     s  s  04d txt      dirname    filename   23    gt   dirname filename 0023 txt    Here s a printf format cheat sheet you might find useful in forming your format string   The printf format is originally from the C function printf  but similar formating functions are available in perl  ruby  python  java  php  etc

User · Answer

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

User · Answer

Can t you just use string formatting of the value before you concat the filename     03d    number

User · Answer

Use String next as the counter    gt  gt  n    000   gt  gt  3 times   puts  file   n next      file 001 file 002 file 003   next is relatively  clever   meaning you can even go for   gt  gt  n    file 000   gt  gt  3 times   puts n next    file 001 file 002 file 003

User · Answer

filenames    000  upto  100   map    index   file   index      Outputs   file 000  file 001  file 002  file 003       file 098  file 099  file 100

[ruby] How can I output leading zeros in Ruby?

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