The permission specification of the FileUtils method is an octal number.

When creating a directory with mkdir_p, I also want to specify the permission ...

About mkdir_p

Create the directory dir and all its parent directories.

For example

require 'fileutils'
FileUtils.mkdir_p('/usr/local/lib/ruby')
Will check all the directories below(If not)Create.

/usr
/usr/local
/usr/local/bin
/usr/local/bin/ruby

Quote https://docs.ruby-lang.org/ja/latest/class/FileUtils.html#M_MAKEDIRS

Try to create by specifying permission

Linux commands ... mkdir -p -m 755 ./hoge1/hoge2/hoge3/ruby ruby

test.rb

require 'fileutils'

FileUtils.mkdir_p('./hoge1/hoge2/hoge3/ruby', mode: 755)

Wonder?

Run immediately

$ ruby test.rb
$ ls -la
d-wxrw--wt    3 casix  staff     96 Jun 12 01:06 hoge1/

No, obviously the authority is not 755 ...

I read the source code of mkdir_p

fileutils.rb

# File fileutils.rb, line 194
def mkdir_p(list, mode: nil, noop: nil, verbose: nil)
  list = fu_list(list)
  fu_output_message "mkdir -p #{mode ? ('-m %03o ' % mode) : ''}#{list.join ' '}" if verbose
  return *list if noop

  ...
end

If you read carefully the processing of the arguments put in mode

mkdir -p #{mode ? ('-m %03o ' % mode) : ''}

a

#{mode ? ('-m %03o ' % mode) : ''}

Should be 755,

'-m %03o ' % mode

If you put 755 in mode

irb(main):001:0> mode = 755
=> 755
irb(main):002:0> '-m %03o ' % mode
=> "-m 1363 "

1363 is returned

That means ...

FileUtils.mkdir_p('./hoge1/hoge2/hoge3/ruby', mode: 755)
# ↓
# $ mkdir -p -m 1363 ./hoge1/hoge2/hoge3/ruby

That it was

It was an octal number, not a decimal number, that should be included in the argument

'-m %03o ' % mode

# %Since 03o is output as a 0-packed 3-digit octal number
#Mode is a number converted from 755 to decimal.(493)Put in

irb(main):001:0> mode = 0o755
=> 493
irb(main):002:0> '-m %03o ' % mode
=> "-m 755 "

Looks good

Try to fix

FileUtils.mkdir_p('./hoge1/hoge2/hoge3/ruby', mode: 0o755)

# FileUtils.mkdir_p('./hoge1/hoge2/hoge3/ruby', mode: 0755)But k

$ ls -la
drwxr-xr-x    3 casix  staff     96 Jun 12 01:43 hoge1/

It seems that it can be set with 755!

In FileUtils, the permission setting was octal, regardless of mkdir_p

It wasn't limited to mkdir_p in the first place All the methods that can specify permission with FileUtils seem to have the same specifications

https://docs.ruby-lang.org/ja/latest/class/FileUtils.html#options

(By the way, it's easy to forget the knowledge that when it starts from 0, it becomes an octal number ...)