freebsd-dev/usr.bin/getconf/getconf.1
Garrett Wollman e9cfb9ae3a Completely revamp the way getconf(1) works, for better adherence to the
intent of the Standard.

- Make getconf able to distinguish between configuration variables which
  are entirely unknown and those which are merely not defined in the
  compilation environment.  The latter now get a more appropriate
  "undefined\n" result rather than a diagnostic.  This may not be
  exactly right, but it's closer to the intent of the Standard than
  the previous behavior.

- Support ``programming environments'' by validating that the environment
  requested with the `-v' flag is the one-and-only execution environment.
  (If more environments are supported for some platforms in the future,
  multiple getconf(1) executables will be required, but a simple edit in
  progenv.gperf will enable automatic support for it.)  Document POSIX
  standard programming environments.

- Add all of the 1003.1-2001 configuration variables.  FreeBSD does not
  support all of these (including some that are mandatory); getconf will
  later be fixed to break the world should a required variable not be
  defined.

As a result of all these changes, gperf is no longer adequate.  Keep the
overall format and names of the files for now, to preserve revision history.
Use an awk script to process the .gperf files into C source, which does a
few things that gperf, as a more general tool, cannot do.  The keyword
recognition function is no longer a perfect hash function.

This may obviate the need for gperf in the source tree.

- Add a small compile-time regression test to break the build if any of the
  .gperf files declare conflicting token sets.  (gperf itself would have done
  this for the simple case of duplicate tokens in the same input file.)
2002-09-19 03:39:03 +00:00

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.Dd September 18, 2002
.Dt GETCONF 1
.Os
.Sh NAME
.Nm getconf
.Nd retrieve standard configuration variables
.Sh SYNOPSIS
.Nm
.Op Fl v Ar environment
.Ar path_var
.Ar file
.Pp
.Nm
.Op Fl v Ar environment
.Ar system_var
.Sh DESCRIPTION
The
.Nm
utility prints the value of a
.Tn POSIX
or
.Tn X/Open
path or system configuration variable to the standard output.
If the specified variable is undefined, the string
.Dq Li undefined
is output.
.Pp
The first form of the command, with two mandatory
arguments, retrieves file- and filesystem-specific
configuration variables using
.Xr pathconf 2 .
The second form, with a single argument, retrieves system
configuration variables using
.Xr confstr 3
and
.Xr sysconf 3 ,
depending on the type of variable.
As an extension, the second form can also be used to query static limits from
.Aq Pa limits.h .
.Pp
All
.Xr sysconf 3
and
.Xr pathconf 2
variables use the same name as the manifest constants defined in
the relevant standard C-language bindings, including any leading
underscore or prefix.
That is to say,
.Ar system_var
might be
.Dv ARG_MAX
or
.Dv _POSIX_VERSION ,
as opposed to the
.Xr sysconf 3
names
.Dv _SC_ARG_MAX
or
.Dv _SC_POSIX_VERSION .
Variables retrieved from
.Xr confstr 3
have the leading
.Ql _CS_
stripped off; thus,
.Dv _CS_PATH
is queried by a
.Ar system_var
of
.Dq Li PATH .
.Ss Programming Environments
The
.Fl v Ar environment
option specifies a
.St -p1003.1-2001
programming environment under which the values are to be queried.
This option currently does nothing, but may in the future be used
to select between 32-bit and 64-bit execution environments on platforms
which support both.
Specifying an environment which is not supported on the current execution
platform gives undefined results.
.Pp
The standard programming environments are as follows:
.Bl -tag -width ".Li POSIX_V6_LPBIG_OFFBIG" -offset indent
.It Li POSIX_V6_ILP32_OFF32
Exactly 32-bit integer, long, pointer, and file offset.
.Sy Supported platforms :
None.
.It Li POSIX_V6_ILP32_OFFBIG
Exactly 32-bit integer, long, and pointer; at least 64-bit file offset.
.Sy Supported platforms :
.Tn IA32 ,
.Tn PowerPC .
.It Li POSIX_V6_LP64_OFF64
Exactly 32-bit integer; exactly 64-bit long, pointer, and file offset.
.Sy Supported platforms :
.Tn Alpha ,
.Tn SPARC64 .
.It Li POSIX_V6_LPBIG_OFFBIG
At least 32-bit integer; at least 64-bit long, pointer, and file offset.
.Sy Supported platforms :
None.
.El
.Pp
The command:
.Bd -literal -offset indent
getconf POSIX_V6_WIDTH_RESTRICTED_ENVS
.Ed
.Pp
returns a newline-separated list of environments in which the width
of certain fundamental types is no greater than the width of the native
C type
.Ql long .
At present, all programming environments supported by
.Fx
have this property.
Several of the
.Xr confstr 3
variables provide information on the necessary compiler and linker flags
to use the standard programming environments described above.
.Sh DIAGNOSTICS
.Ex -std
Use of a
.Ar system_var
or
.Ar path_var
which is completely unrecognized is considered an error,
causing a diagnostic message to be written to standard error.
One
which is known but merely undefined does not result in an error
indication.
The
.Nm
command recognizes all of the variables defined for
.St -p1003.1-2001 ,
including those which are not currently implemented.
.Sh EXAMPLES
The command:
.Bd -literal -offset indent
getconf PATH
.Ed
.Pp
will display the system default setting for the
.Ev PATH
environment variable.
.Pp
The command:
.Bd -literal -offset indent
getconf NAME_MAX /tmp
.Ed
.Pp
will display the maximum length of a filename in the
.Pa /tmp
directory.
.Pp
The command:
.Bd -literal -offset indent
getconf -v POSIX_V6_LPBIG_OFFBIG LONG_MAX
.Ed
.Pp
will display the maximum value of the C type
.Ql long
in the
.Li POSIX_V6_LPBIG_OFFBIG
programming environment,
if the system supports that environment.
.Sh SEE ALSO
.Xr pathconf 2 ,
.Xr confstr 3 ,
.Xr sysconf 3
.Sh STANDARDS
The
.Nm
utility is expected to be compliant with
.St -p1003.1-2001 .
.Sh HISTORY
The
.Nm
command first appeared in
.Fx 5.0 .
.Sh AUTHORS
.An Garrett A. Wollman Aq wollman@lcs.mit.edu