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Picking POSIX semaphore names

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  Picking POSIX semaphore names Hallvard Breien Furuseth <h.b.furuseth@usit.uio.no> - 2012-04-26 19:22 +0200
    Re: Picking POSIX semaphore names Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2012-04-26 20:13 +0200

#853 — Picking POSIX semaphore names

POSIX only defines the behaviour of semaphore names that start with a
slash and contain no other slashes.  But have users always access to
create such names?  They can show up in the filesystem, and non-root
users do not have access to create entries in the root directory.

For that matter, it sounds annoying if "ls /" lists a large number of
named semaphores.  Have any conventions emerged for where to put them
on systems where their names do show up in the filesystem?  /tmp/
springs to mind - on systems where that works, anyway.

-- 
Hallvard

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#854

Hallvard Breien Furuseth <h.b.furuseth@usit.uio.no> writes:

> POSIX only defines the behaviour of semaphore names that start with a
> slash and contain no other slashes.  But have users always access to
> create such names?  They can show up in the filesystem, and non-root
> users do not have access to create entries in the root directory.

Semaphore names are logical names, not paths or filenames.

> For that matter, it sounds annoying if "ls /" lists a large number of
> named semaphores.  Have any conventions emerged for where to put them
> on systems where their names do show up in the filesystem?  /tmp/
> springs to mind - on systems where that works, anyway.

From "man sem_overview" on Linux:

| Accessing named semaphores via the file system
|     On Linux, named semaphores are created in a virtual file system,
|     nor‐ mally mounted under /dev/shm, with names of the form
|     sem.somename. (This is the reason that semaphore names are limited
|     to NAME_MAX-4 rather than NAME_MAX characters.)

I guess other systems use similar locations.

-- Alain.

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