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+@chapter System Configuration Limits
+@node System Configuration Limits
+
+The functions and macros listed in this chapter describe various operating
+system limits.
+
+@iftex
+@itemize @bullet
+
+@item
+@ref{File System Parameters}, contains informations about constants and 
+functions that describe various file system limits, such as the maximum
+length of a file name.
+
+@item
+@ref{System Parameters}, contains information about constants and functions
+that describe various process-related limits (such as the maximum number
+of processes that can belong to a single user) and optional features supported
+by the operating system.
+
+@item
+@ref{String-Valued Parameters}, contains information about additional
+constants and functions for string-valued system parameters.
+@end itemize
+@end iftex
+
+@menu
+* File System Parameters::	Constants and functions that describe
+				 various file system limits.
+
+* System Parameters::		Constants and functions that describe
+				 various process-related limits.
+
+* String-Valued Parameters::	Constants and functions that describe
+				 string-valued limits.
+@end menu
+
+
+@node File System Parameters
+@section File System Parameters
+
+The POSIX.1 standard specifies a number of symbolic constants that
+represent the values for certain limits related to the file system, such
+as the maximum length of a file name component.  However, some of these
+limits might not really be constants in a given implementation.  For
+example, in a nonhomogeneous networked environment, files mounted from
+different hosts might be subject to different sets of limitations.
+
+In order to deal with the problem of variable limits, for most of these
+parameters there is one symbolic constant that defines the most
+restrictive limit permissible by the POSIX standard.  If the actual
+limit placed by a particular implementation for that parameter is a
+constant, then it defines another constant to represent it.  Otherwise,
+the actual limit that applies to a particular file can be requested at
+runtime by calling @code{pathconf} or @code{fpathconf}.
+
+Except for @code{FILENAME_MAX}, which is defined in @file{<stdio.h>},
+definitions for the following symbolic constants appear in the header
+file @file{<limits.h>}.  All of these macros expand into integer
+constant values.
+
+@strong{Incomplete:}  What does the GNU system do?
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_LINK_MAX
+This macro represents the most restrictive limit permitted by POSIX
+for the maximum value of a file's link count.  The value of this
+constant is @code{8}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro LINK_MAX
+This is the actual implementation limit corresponding to
+@code{_POSIX_LINK_MAX}, but is defined only if the limit for the
+particular implementation is constant for all files.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_MAX_CANON
+This macro represents the most restrictive limit permitted by POSIX
+for the maximum number of bytes in a canonical input line from a
+terminal device.  The value of this constant is @code{255}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro MAX_CANON
+This is the actual implementation limit corresponding to
+@code{_POSIX_MAX_CANON}, but is defined only if the limit for the
+particular implementation is constant for all files.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_MAX_INPUT
+This macro represents the most restrictive limit permitted by POSIX for
+the maximum number of bytes in a terminal device input queue (or
+typeahead buffer).  @xref{Input Modes}.  The value of this constant is
+@code{255}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro MAX_INPUT
+This is the actual implementation limit corresponding to
+@code{_POSIX_MAX_INPUT}, but is defined only if the limit for the
+particular implementation is a constant for all files.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_NAME_MAX
+This macro represents the most restrictive limit permitted by POSIX for
+the maximum number of bytes in a file name component.  The value of this
+constant is @code{14}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro NAME_MAX
+This is the actual implementation limit corresponding to
+@code{_POSIX_NAME_MAX}, but is defined only if the limit for the
+particular implementation is a constant for all files.
+@end defvr
+
+@comment dirent.h
+@comment BSD, GNU
+@defvr Macro MAXNAMLEN
+This is the BSD name for @code{NAME_MAX}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_PATH_MAX
+This macro represents the most restrictive limit permitted by POSIX for
+the maximum number of bytes in a file name.  The value of this constant
+is @code{255}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro PATH_MAX
+This is the actual implementation limit corresponding to
+@code{_POSIX_PATH_MAX}, but is defined only if the limit for the
+particular implementation is a constant for all files.
+@end defvr
+
+@comment stdio.h
+@comment ANSI
+@defvr {Macro} FILENAME_MAX 
+The value of this macro is an integer constant expression that
+represents the maximum length of a file name string.
+
+Unlike @code{PATH_MAX}, this macro is defined even if there is no actual
+limit imposed.  In such a case, its value is typically a very large
+number.  Don't try to use @code{FILENAME_MAX} as the size of an
+array in which to store a file name!  Use dynamic allocation
+(@pxref{Memory Allocation}) instead.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_PIPE_BUF
+This macro represents the most restrictive limit permitted by POSIX for
+the maximum number of bytes that can be written atomically to a pipe.
+If multiple processes are writing to the same pipe simultaneously,
+output from different processes might appear in interleaved chunks of
+this size.  The value of this constant is @code{512}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _PIPE_BUF
+This is the actual implementation limit corresponding to
+@code{_POSIX_PIPE_BUF}, but is defined only if the limit for the
+particular implementation is a constant for all pipes and FIFO files.
+@end defvr
+
+
+There are also these macros which may be defined in @file{<unistd.h>} to
+describe additional characteristics of the file system.  If any of these
+macros are not defined at all, then the corresponding parameter depends
+on the file to which it is applied, and you must use the @code{pathconf}
+function at runtime to determine the parameter value.  If the value is
+defined to be @code{-1}, then the option does not apply to any file.
+Otherwise, the option applies to all files.
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _POSIX_CHOWN_RESTRICTED
+If this option is enabled, the @code{chown} function is restricted so
+that the only changes permitted to nonprivileged processes is to change 
+the group owner of a file to either be the effective group ID of the
+process, or one of its supplementary group IDs.  @xref{File Ownership}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _POSIX_NO_TRUNC
+If this option is enabled, file name components longer than @code{NAME_MAX}
+generate an @code{ENAMETOOLONG} error.  Otherwise, file name components
+that are too long are silently truncated.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _POSIX_VDISABLE
+This option is only meaningful for files that are terminal devices.
+If it is enabled, then handling for special control characters can
+be disabled individually.  @xref{Special Characters}.
+@end defvr
+
+For each of the above parameters, if the value is not a constant
+for all files, you can request the value that applies to a particular
+file using the @code{pathconf} or @code{fpathconf}.  These functions 
+and the associated @var{parameter} constants are declared in the
+header file @file{<unistd.h>}.
+
+@comment unistd.h
+@comment POSIX.1
+@deftypefun long pathconf (const char *@var{filename}, int @var{parameter})
+This function is used to inquire about the limits that apply to
+the file named @var{filename}.
+
+The @var{parameter} argument should be one of the @samp{_PC_} constants
+listed below.
+
+The normal return value from @code{pathconf} is the value you requested.
+A value of @code{-1} is returned both if the implementation does not
+impose a limit, and in case of an error.  In the former case, @code{errno}
+is not set, while in the latter case, @code{errno} is set to indicate
+the cause of the problem.  Besides the usual file name syntax errors
+(@pxref{File Name Errors}), the following error conditions are defined
+for this function:
+
+@table @code
+@item EINVAL
+The value of @var{parameter} is invalid, or the implementation doesn't
+support the @var{parameter} for the specific file.
+@end table
+@end deftypefun
+
+@comment unistd.h
+@comment POSIX.1
+@deftypefun long fpathconf (int @var{filedes}, int @var{parameter})
+This is just like @code{pathconf} except that an open file descriptor
+is used to specify the file for which information is requested, instead
+of a file name.
+
+The following @code{errno} error conditions are defined for this function:
+
+@table @code
+@item EBADF
+The @var{filedes} argument is not a valid file descriptor.
+
+@item EINVAL
+The value of @var{parameter} is invalid, or the implementation doesn't
+support the @var{parameter} for the specific file.
+@end table
+@end deftypefun
+
+These symbolic constants are defined for use as the @var{parameter}
+argument to @code{pathconf} and @code{fpathconf}.  The values are
+all integer constants.
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _PC_LINK_MAX
+Inquire about the parameter corresponding to @code{LINK_MAX}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _PC_MAX_CANON
+Inquire about the parameter corresponding to @code{MAX_CANON}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _PC_MAX_INPUT
+Inquire about the parameter corresponding to @code{MAX_INPUT}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _PC_NAME_MAX
+Inquire about the parameter corresponding to @code{NAME_MAX}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _PC_PATH_MAX
+Inquire about the parameter corresponding to @code{PATH_MAX}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _PC_PIPE_BUF
+Inquire about the parameter corresponding to @code{PIPE_BUF}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _PC_CHOWN_RESTRICTED
+Inquire about the parameter corresponding to @code{_POSIX_CHOWN_RESTRICTED}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _PC_NO_TRUNC
+Inquire about the parameter corresponding to @code{_POSIX_NO_TRUNC}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _PC_VDISABLE
+Inquire about the parameter corresponding to @code{_POSIX_VDISABLE}.
+@end defvr
+
+
+@node System Parameters
+@section System Parameters
+
+The POSIX.1 and POSIX.2 standards specify a number of symbolic constants that
+represent the values for certain system limits, such as the maximum
+number of simultaneous processes per user.  However, some of these
+limits might not really be constant in a given implementation.  In a
+typical Unix environment, for example, the values are determined from a
+configuration file used in building the operating system kernel, and can
+be changed without invalidating already-compiled programs by rebooting
+the machine with a different kernel.  Other parameters might depend on
+the amount of memory available.
+
+In order to deal with the problem of variable limits, for most of these
+parameters there is one symbolic constant that defines the most
+restrictive limit permissible by the POSIX standard.  If the actual
+limit placed by a particular implementation for that parameter is a
+constant, then it defines another symbolic constant to represent it.
+Otherwise, the actual limit can be requested at runtime by calling the
+@code{sysconf} function.
+
+Definitions for the following macros appear in the header file
+@file{<limits.h>}.  The values of the macros are all integer constants.
+
+@strong{Incomplete:}  What does the GNU system do for the 
+implementation-defined macros?
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_ARG_MAX
+The value of this macro is the most restrictive limit permitted by POSIX
+for the maximum combined length of the @var{argv} and @var{environ}
+arguments that can be passed to the @code{exec} functions.  The value of
+this constant is @code{4096}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro ARG_MAX
+This is the actual implementation limit corresponding to
+@code{_POSIX_ARG_MAX}, but is defined only if the limit for the
+particular implementation is a constant.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_CHILD_MAX
+The value of this macro is the most restrictive limit permitted by POSIX
+for the maximum number of simultaneous processes per real user ID.  Its
+value is @code{6}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro CHILD_MAX
+This is the actual implementation limit corresponding to
+@code{_POSIX_CHILD_MAX}, but is defined only if the limit for the
+particular implementation is a constant.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_OPEN_MAX
+The value of this macro is the most restrictive limit permitted by POSIX
+for the maximum number of files that a single process can have open
+simultaneously.  The value of this constant is @code{16}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro OPEN_MAX
+This is the actual implementation limit corresponding to
+@code{_POSIX_OPEN_MAX}, but is defined only if the limit for the
+particular implementation is a constant.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_STREAM_MAX
+The value of this macro is the most restrictive limit permitted by POSIX
+for the maximum number of streams that a single process can have open
+simultaneously.  The value of this constant is @code{8}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro STREAM_MAX
+This is the actual implementation limit corresponding to
+@code{_POSIX_STREAM_MAX}, but is defined only if the limit for the
+particular implementation is a constant.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_TZNAME_MAX
+The value of this macro is the most restrictive limit permitted by POSIX
+for the maximum length of a time zone name.  The value of this constant
+is @code{3}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro TZNAME_MAX
+This is the actual implementation limit corresponding to
+@code{_POSIX_TZNAME_MAX}, but is defined only if the limit for the
+particular implementation is a constant.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_NGROUPS_MAX
+The value of this macro is the most restrictive limit permitted by POSIX
+for the maximum number of supplementary group IDs per process.  The
+value of the constant is @code{0}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro NGROUPS_MAX
+This corresponds to @code{_POSIX_NGROUPS_MAX}, but represents the
+minimum value guaranteed by the implementation.  This macro is defined
+even if the limit for the particular implementation is not a constant.
+(The actual maximum might be larger, and can be accessed with the
+@code{sysconf} function.)
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro _POSIX_SSIZE_MAX
+The value of this macro is the most restrictive limit permitted by POSIX
+for the maximum value that can be stored in an object of type @code{ssize_t}.
+(Effectively, this is the limit on the number of bytes that can be read
+or written in a single operation.  The value of this constant is
+@code{32767}.
+@end defvr
+
+@comment limits.h
+@comment POSIX.1
+@defvr Macro SSIZE_MAX
+This is the actual implementation limit corresponding to
+@code{_POSIX_SSIZE_MAX}.  This macro is always defined and its value is
+a constant within a given implementation.
+@end defvr
+
+Definitions for these additional macros that describe system parameters
+appear in the header file @file{<unistd.h>}.
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _POSIX_JOB_CONTROL
+If this symbol is defined, it indicates that the system supports job
+control.  Otherwise, the implementation behaves as if all processes
+within a session belong to a single process group.  @xref{Job Control}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _POSIX_SAVED_IDS
+If this symbol is defined, it indicates that the system remembers the
+effective user and group IDs of an executable file with the set-user-ID
+or set-group-ID bits set, and that explicitly changing the effective
+user or group IDs back to these values is permitted.  If this option is
+not defined, then if a nonprivileged process changes its effective user
+or group ID to the real user or group ID of the process, it can't change
+it back again.  @xref{User/Group IDs of a Process}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _POSIX_VERSION
+This constant represents the version of the POSIX standard to which
+the implementation conforms.  For an implementation conforming to the
+1990 POSIX.1 standard, the value is the integer @code{199009L}.
+@end defvr
+
+You can request the actual runtime values of these parameters using the
+@code{sysconf} function.  This function and the macros for use as its
+@var{parameter} argument are declared in the header file
+@file{<unistd.h>}.
+
+@comment unistd.h
+@comment POSIX.1
+@deftypefun long sysconf (int @var{parameter})
+This function is used to inquire about runtime system parameters.
+The @var{parameter} argument should be one of the @samp{_SC_} macros
+listed below.
+
+The normal return value from @code{sysconf} is the value you requested.
+A value of @code{-1} is returned both if the implementation does not
+impose a limit, and in case of an error.  
+
+The following @code{errno} error conditions are defined for this function:
+@table @code
+@item EINVAL
+The value of the @var{parameter} is invalid.
+@end table
+@end deftypefun
+
+These symbolic constants are defined for use as the @var{parameter}
+argument to @code{sysconf}.  The values are all integer constants.
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _SC_ARG_MAX
+Inquire about the parameter corresponding to @code{ARG_MAX}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _SC_CHILD_MAX
+Inquire about the parameter corresponding to @code{CHILD_MAX}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _SC_OPEN_MAX
+Inquire about the parameter corresponding to @code{OPEN_MAX}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _SC_STREAM_MAX
+Inquire about the parameter corresponding to @code{STREAM_MAX}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _SC_TZNAME_MAX
+Inquire about the parameter corresponding to @code{TZNAME_MAX}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _SC_NGROUPS_MAX
+Inquire about the parameter corresponding to @code{NGROUPS_MAX}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _SC_JOB_CONTROL
+Inquire about the parameter corresponding to @code{_POSIX_JOB_CONTROL}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _SC_SAVED_IDS
+Inquire about the parameter corresponding to @code{_POSIX_SAVED_IDS}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _SC_VERSION
+Inquire about the parameter corresponding to @code{_POSIX_VERSION}.
+@end defvr
+
+@comment unistd.h
+@comment POSIX.1
+@defvr Macro _SC_CLK_TCK
+Inquire about the parameter corresponding to @code{CLOCKS_PER_SEC};
+@pxref{Basic Elapsed CPU Time Inquiry}.
+@end defvr
+
+@strong{Incomplete:}  There are also a bunch of symbols for POSIX.2
+features listed in @file{<unistd.h>}.
+
+
+@node String-Valued Parameters
+@section String-Valued Parameters
+
+@strong{Incomplete:}  The POSIX.2 @code{confstr} function goes here.