.TH "register_sysctl_table" 9 "register_sysctl_table" "25 May 1998" "Kernel Hacker's Manual" LINUX
.SH NAME
register_sysctl_table \-  register a sysctl hierarchy
.SH SYNOPSIS
.B "struct ctl_table_header *" register_sysctl_table
.BI "(ctl_table *" table ","
.BI "int " insert_at_head ");"
.SH ARGUMENTS
.IP "table" 12
 the top-level table structure
.IP "insert_at_head" 12
 whether the entry should be inserted in front or at the end
.SH "DESCRIPTION"
Register a sysctl table hierarchy. \fItable\fP should be a filled in ctl_table
array. An entry with a ctl_name of 0 terminates the table. 

The members of the \fBctl_table\fP structure are used as follows:

ctl_name - This is the numeric sysctl value used by sysctl(2). The number
must be unique within that level of sysctl

procname - the name of the sysctl file under /proc/sys. Set to NULL to not
enter a sysctl file

data - a pointer to data for use by proc_handler

maxlen - the maximum size in bytes of the data

mode - the file permissions for the /proc/sys file, and for sysctl(2)

child - a pointer to the child sysctl table if this entry is a directory, or
NULL.

proc_handler - the text handler routine (described below)

strategy - the strategy routine (described below)

de - for internal use by the sysctl routines

extra1, extra2 - extra pointers usable by the proc handler routines

Leaf nodes in the sysctl tree will be represented by a single file
under /proc; non-leaf nodes will be represented by directories.

sysctl(2) can automatically manage read and write requests through
the sysctl table.  The data and maxlen fields of the ctl_table
struct enable minimal validation of the values being written to be
performed, and the mode field allows minimal authentication.

More sophisticated management can be enabled by the provision of a
strategy routine with the table entry.  This will be called before
any automatic read or write of the data is performed.

The strategy routine may return

< 0 - Error occurred (error is passed to user process)

0   - OK - proceed with automatic read or write.

> 0 - OK - read or write has been done by the strategy routine, so
return immediately.

There must be a proc_handler routine for any terminal nodes
mirrored under /proc/sys (non-terminals are handled by a built-in
directory handler).  Several default handlers are available to
cover common cases -

\fBproc_dostring\fP, \fBproc_dointvec\fP, \fBproc_dointvec_jiffies\fP,
\fBproc_dointvec_minmax\fP, \fBproc_doulongvec_ms_jiffies_minmax\fP,
\fBproc_doulongvec_minmax\fP

It is the handler's job to read the input buffer from user memory
and process it. The handler should return 0 on success.

This routine returns NULL on a failure to register, and a pointer
to the table header on success.