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Full Discussion: POSIX message queue size
Operating Systems Linux POSIX message queue size Post 302202588 by Vourhey on Thursday 5th of June 2008 08:09:43 AM
Old 06-05-2008
The default queue size is 819200 bytes. We can change this value by invoking "ulimit -q". But it only changes the queue size for the current shell and applications run by it. I have some application that must be invoked on system start (before login in and starting shell). And i need to increase the queue size for them. But i can't use "ulimit -q" command. Because the shell hasn't been started yet.
Also i can't use the "/etc/limits.conf" file to specify queue size. Because: "note that all limit settings are set per login. They are not global, nor are they permanent".
 

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ulimit(2)							   System Calls 							 ulimit(2)

NAME
ulimit - get and set process limits SYNOPSIS
#include <ulimit.h> long ulimit(int cmd, /* newlimit */...); DESCRIPTION
The ulimit() function provides for control over process limits. It is effective in limiting the growth of regular files. Pipes are limited to PIPE_MAX bytes. The cmd values, defined in <ulimit.h>, include: UL_GETFSIZE Return the soft file size limit of the process. The limit is in units of 512-byte blocks and is inherited by child pro- cesses. Files of any size can be read. The return value is the integer part of the soft file size limit divided by 512. If the result cannot be represented as a long int, the result is unspecified. UL_SETFSIZE Set the hard and soft file size limits for output operations of the process to the value of the second argument, taken as a long int. Any process may decrease its own hard limit, but only a process with appropriate privileges may increase the limit. The new file size limit is returned. The hard and soft file size limits are set to the specified value multiplied by 512. If the result would overflow an rlimit_t, the actual value set is unspecified. UL_GMEMLIM Get the maximum possible break value (see brk(2)). UL_GDESLIM Get the current value of the maximum number of open files per process configured in the system. RETURN VALUES
Upon successful completion, ulimit() returns the value of the requested limit. Otherwise, -1 is returned, the limit is not changed, and errno is set to indicate the error. ERRORS
The ulimit() function will fail if: EINVAL The cmd argument is not valid. EPERM A process that has not asserted {PRIV_SYS_RESOURCE} in its effective set is trying to increase its file size limit. USAGE
Since all return values are permissible in a successful situation, an application wishing to check for error situations should set errno to 0, then call ulimit(), and if it returns -1, check if errno is non-zero. The getrlimit() and setrlimit() functions provide a more general interface for controlling process limits, and are preferred over ulimit(). See getrlimit(2). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
brk(2), getrlimit(2), write(2), attributes(5), privileges(5), standards(5) SunOS 5.10 1 Feb 2003 ulimit(2)
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