NAME

SYNOPSIS

DESCRIPTION

Unlinking removes the name from the system and, when the last process unmaps the segment and closes file descriptor pointing to the segment, frees underlying memory.

The number of hard links as displayed by the stat subcommand, is equal to the number of references to the underlying VM object. It is almost always equal to the number of mappings +1, except for transient references.

The following subcommands are provided:

create

Create segments with the specified paths, if not exist. The mode optional numerical argument specifies initial access mode.

rm

Unlink the paths specified.

ls

List all linked named shared memory segments visible to the caller. For each segment, the user and group owner, size, and path are displayed. The -j option limits the output to segments within the specified jail name or id.

dump

Output raw bytes values from the segment to standard output.

stat

Print metadata for the specified path, in the format similar to the stat(1) utility.

truncate

Change the length of the segments. Argument to the -s option specifies new length. The human-friendly 'k', 'm', 'g' suffixes can be used, see expand_number(3). If the option is not specified, assumed length is zero.

For some commands, the following options may be provided:

-h

If specified, requests human-readable display of size, see humanize_number(3).

-n

Prevent translation of owner and group into symbolic names using name-switch services, instead the raw numeric values are printed.

EXIT STATUS

EXAMPLES

• To show content of the shared memory segment with the path /1, use the command
  posixshmcontrol dump /1 | hexdump -C
• To create a segment with the path /2 and then enlarge it to 1M, use the sequence of commands
  posixshmcontrol create /2
  posixshmcontrol truncate -s 1m /2

SEE ALSO

HISTORY

AUTHORS