I like to present a challenge to my software engineer friends: can you tell me what this command does on Linux, if run in an empty directory?
mkdir -m 0755 -p ./usr/bin/foo If they read the mkdir man page ( https://man7.org/linux/man-pages/man1/mkdir.1.html), they almost always say the answer is: - create the directory ./usr, with the mode 0755 - create the directory ./usr/bin, with the mode 0755 - create the directory ./usr/bin/foo, with the mode 0755 They are wrong. (Side note -- this misunderstanding contributed to one of the scariest outages Google has ever seen, https://www.pdl.cmu.edu/SDI/2012/083012b.html). What it actually does: - create the directory ./usr, with the mode based on the umask - create the directory ./usr/bin, with the mode based on the umask - create the directory ./usr/bin/foo, with the mode 0755 I tried at the time to get the man page corrected, but I was told at the time that nobody reads man pages, and the info page is correct, so it won't be fixed. I figured after almost 10 years, perhaps thinking has evolved. Can we fix the man page? I have a suggested fix: the current man page reads: -p, --parents no error if existing, make parent directories as needed I can be updated to read: -p, --parents no error if existing, make parent directories as needed, setting their file permission bits to the umask modified by ‘u+wx’. I copied the new text from the info page. Thanks! Chris
