问题
So this doesn't seem like a terribly complicated question I have, but it's one I can't find the answer to. I'm confused about what the -p option does in Unix. I used it for a lab assignment while creating a subdirectory and then another subdirectory within that one. It looked like this:
mkdir -p cmps012m/lab1
This is in a private directory with normal rights (rlidwka). Oh, and would someone mind giving a little explanation of what rlidwka means? I'm not a total noob to Unix, but I'm not really familiar with what this means. Hopefully that's not too vague of a question.
回答1:
The man pages is the best source of information you can find... and is at your fingertips: man mkdir yields this about -p switch:
-p, --parents
no error if existing, make parent directories as needed
Use case example: Assume I want to create directories hello/goodbye but none exist:
$mkdir hello/goodbye
mkdir:cannot create directory 'hello/goodbye': No such file or directory
$mkdir -p hello/goodbye
$
-p created both, hello and goodbye
This means that the command will create all the directories necessaries to fulfill your request, not returning any error in case that directory exists.
About rlidwka, Google has a very good memory for acronyms :). My search returned this for example: http://www.cs.cmu.edu/~help/afs/afs_acls.html
Directory permissions
l (lookup)
Allows one to list the contents of a directory. It does not allow the reading of files.
i (insert)
Allows one to create new files in a directory or copy new files to a directory.
d (delete)
Allows one to remove files and sub-directories from a directory.
a (administer)
Allows one to change a directory's ACL. The owner of a directory can always change the ACL of a directory that s/he owns, along with the ACLs of any subdirectories in that directory.
File permissions
r (read)
Allows one to read the contents of file in the directory.
w (write)
Allows one to modify the contents of files in a directory and use chmod on them.
k (lock)
Allows programs to lock files in a directory.
Hence rlidwka means: All permissions on.
It's worth mentioning, as @KeithThompson pointed out in the comments, that not all Unix systems support ACL. So probably the rlidwka concept doesn't apply here.
回答2:
mkdir [-switch] foldername
-p is a switch which is optional, it will create subfolder and parent folder as well even parent folder doesn't exist.
From the man page:
-p, --parents no error if existing, make parent directories as needed
Example:
mkdir -p storage/framework/{sessions,views,cache}
This will create subfolder sessions,views,cache inside framework folder irrespective of 'framework' was available earlier or not.
回答3:
-p|--parent will be used if you are trying to create a directory with top-down approach. That will create the parent directory then child and so on iff none exists.
-p, --parents no error if existing, make parent directories as needed
About rlidwka it means giving full or administrative access. Found it here https://itservices.stanford.edu/service/afs/intro/permissions/unix.
回答4:
Note that -p is an argument to the mkdir command specifically, not the whole of Unix. Every command can have whatever arguments it needs.
In this case it means "parents", meaning mkdir will create a directory and any parents that don't already exist.
回答5:
PATH: Answered long ago, however, it maybe more helpful to think of -p as "Path" (easier to remember), as in this causes mkdir to create every part of the path that isn't already there.
mkdir -p /usr/bin/comm/diff/er/fence
if /usr/bin/comm already exists, it acts like: mkdir /usr/bin/comm/diff mkdir /usr/bin/comm/diff/er mkdir /usr/bin/comm/diff/er/fence
As you can see, it saves you a bit of typing, and thinking, since you don't have to figure out what's already there and what isn't.
来源：https://stackoverflow.com/questions/22737933/mkdirs-p-option