Puzzled by terminology

YorkshireSam · 09-22-2018, 03:14 AM

During my 'studies' I have been using many man pages and am often left puzzled by some of the terminology used. In particular while studying user administration I have been investigating the id command.
There are two options used with this command that return a rather obscure message. The id -n and id -r both return the message that 'it cannot print only names or real id's in default format' For the life of me I cannot fathom out exactly what this actually means. Can anyone shed any light or am I being particularly dense?

Michael Uplawski · 09-22-2018, 03:23 AM

Quote:

Originally Posted by YorkshireSam

The id -n and id -r both return the message that 'it cannot print only names or real id's in default format'

Hit, sunk!
You found a documentation bug.

On the other hand, if you look in the man-page, you see three possible options in parenthesis. What you need to know (but nobody is obliged to), is that "with" means in reality: “This option only works with one of the following three, never more than one of them, though”.
Like in:

id -n -u
id -n -g
id -n -G

But have mercy with the authors. The necessity to reformulate, often arises only after a few people have complained. Many do never complain, though. And my own wisdom I got from consulting the German version of the man-page, which can (or not) hint at an improvement during translation...

One of the best bosses in the world (I was a lucky guy) insisted on a very verbose documentation style and on the expression also of all “implicitly clear” facts, as they never are to everybody.

But software developers are sometimes proud of the confusion they create. And some people are proud of the confusion they create, without even being software developers.

... I say: Keep Them Coming! Someone will straighten that out, if we make enough noise.

aragorn2101 · 09-22-2018, 03:29 AM

Hi, and welcome to LQ,

For the "-n" and the "-r" options, we see from the man pages:

Code:

       -n, --name
              print a name instead of a number, for -ugG

       -r, --real
              print the real ID instead of the effective ID, with -ugG

Actually, we are being instructed that -n and -r options are not to be used alone but together with -u, -g or -G. So, below is an example:

Code:

user1@desktop:~$ id -n
id: cannot print only names or real IDs in default format
user1@desktop:~$ id -r
id: cannot print only names or real IDs in default format
user1@desktop:~$ id -u
1000
user1@desktop:~$ id -n -u
user1
user1@desktop:~$ id -g
1000
user1@desktop:~$ id -n -g
user1
user1@desktop:~$ id -r -g
1000
user1@desktop:~$ id -G
1000 11 17 18 19 20 80 90 100
user1@desktop:~$ id -n -G
user1 floppy audio video cdrom games apache pop users
user1@desktop:~$ id -r -G
1000 11 17 18 19 20 80 90 100

Michael Uplawski · 09-22-2018, 03:38 AM

Quote:

Originally Posted by aragorn2101

Actually, we are being instructed

You are of course right, in a way.
But the word “to instruct” might need a new definition. Meriam-Webster:

Quote:

1 : to give knowledge to : teach, train

2 : to provide with authoritative information or advice the judge instructed the jury

3 : to give an order or command to : direct

From the man-page:

Quote:

with

YorkshireSam · 09-22-2018, 06:36 AM

Thank you Aragorn
Now you have pointed it out... its bl..... obvious.. Thank you.
Actually, we are being instructed that -n and -r options are not to be used alone but together with -u, -g or -G. So, below is an example:

Habitual · 09-24-2018, 12:50 PM

Quote:

Originally Posted by YorkshireSam

Thank you Aragorn
Now you have pointed it out... its bl..... obvious.. Thank you.
Actually, we are being instructed that -n and -r options are not to be used alone but together with -u, -g or -G. So, below is an example:

Not necessarily true for all CMDs/utilities!

-x is the "short option" or switch and
--x would be the "long option" or switch.

take

Code:

ls -al

as an example,
The long options are better at conveying intent, thus you don't need to consult the man page when you read

Code:

ls --almost-all --dereference

says this.
I believe people got tired of the long option switches back the olden days and asked devs for short ones.
Not all long options have short options. So As usual

Code:

man <utility>

is the place to look.

On my mac, there is no short "-r" for the id command.

Sometime they just aren't documented correctly.
I think that's why we're supposed to "check" /usr/local/share/doc/<utility>
under such conditions.

Have fun.