The Linux Programming Interface: a linux and unix system Programming Handbook
tải về 6.93 Mb. Chế độ xem pdf
|
| 935
45.7 Obtaining a List of All IPC Objects Linux provides two nonstandard methods of obtaining a list of all IPC objects on the system: z files within the /proc/sysvipc directory that list all IPC objects; and z the use of Linux-specific ctl calls. We describe the files in /proc/sysvipc directory here, and defer discussion of the ctl calls until Section 46.6, where we provide an example program that lists all System V message queues on the system. Some other UNIX implementations have their own nonstandard methods of obtaining a list of all IPC identifiers; for example, Solaris provides the msgids(), semids(), and shmids() system calls for this purpose. Three read-only files in the /proc/sysvipc directory provide the same information as can be obtained via ipcs: z /proc/sysvipc/msg lists all messages queues and their attributes. z /proc/sysvipc/sem lists all semaphore sets and their attributes. z /proc/sysvipc/shm lists all shared memory segments and their attributes. Unlike the ipcs command, these files always show all objects of the corresponding type, regardless of whether read permission is available on the objects. An example of the contents of /proc/sysvipc/sem is the following (with some white space removed to fit this example on the page): $ cat /proc/sysvipc/sem key semid perms nsems uid gid cuid cgid otime ctime 0 16646144 600 4 1000 100 1000 100 0 1010166460 The three /proc/sysvipc files provide a (nonportable) method for programs and scripts to walk through a list of all of the existing IPC objects of a given type. The best that we can achieve by way of a portable approach to obtaining a list of all IPC objects of a given type is to parse the output of ipcs(1). tải về 6.93 Mb. Chia sẻ với bạn bè của bạn:
|