common/man/ast.3

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 AST 3
 NAME
ast - miscellaneous libast support
 SYNOPSIS
.EX
#include <ast.h>

char* astconf(const char* name, const char* path, const char* value);
Ast_confdisc_t astconfdisc(Ast_confdisc_t new_notify);
void astconflist(Sfio_t* stream, const char* path, int flags);
off_t astcopy(int rfd, int wfd, off_t n);
int astquery(int fd, const char* format , ...);

 DESCRIPTION
.L astconf
is a string interface to the
 confstr (2),  pathconf (2), and
 sysconf (2) calls.
If
 value is
.L 0
then the configuration parameter value for
 name is returned.
Some
 name configuration parameters may consult the
 path argument.
In this case if
 path is
.L 0
then
\f5"/"
is used.
Otherwise if
 path is not
.L 0
then it must exist.
The string return value for
 name remains unchanged until the next
.L astconf
call on
 name . If
 value is
.L 0
then a valid string is always returned;
\f5""
is returned if
 name has no configuration value.
This simplifies the programming interface:
.EX
if (!strcmp(astconf("PATH_RESOLVE", NiL, NiL), "logical"))
 /* the logical way ... */

If
 value is not
.L 0
then the configuration parameter value for
 name is set to
 value . .L 0
is returned if the value cannot be set.
The paradigm is:
.EX
universe = astconf("UNIVERSE", 0, "att");
\|.\|.\|.
astconf("UNIVERSE", 0, universe);

The settable configuration names are:

.L FS_3D
.L 1
if
 3d (1) viewpathing is enabled,
.L 0
otherwise.
This is an alternative to the
 fs3d (3) interface.

.L PATH_RESOLVE
.L logical
if symbolic links are followed during file tree traversal,
.L physical
if symbolic links are not followed during file tree traversal,
and
.L metaphysical
if symbolic links are followed at the top level during file tree traversal.
These correspond to the generic
.LR -L ,
.LR -P ,
and
.L -H
command options.

.L UNIVERSE
.L ucb
for
 Berkeley style and
.L att
otherwise.
This configuration parameter controls the
 universe setting on machines that support it (e.g., Pyramid).
.L UNIVERSE
also controls the behavior of some commands like
 cat (1) and
 echo (1).
User defined
 name values may also be set and queried, but these should probably have
some form of vendor prefix to avoid being stomped by future standards.

.L astconfdisc
registers a discipline function
.EX
int (*notify)(const char* name, const char* path, const char* value);

that is called just before the configuration parameter
 name is set to
 value relative to
 path . If
 notify returns
.L 0
then the configuration parameter value is not changed.

.L astconflist
lists the current configuration names and values of
 stream . If
 path is
.L 0
then \f5"/" is used where appropriate.
If
 flags is
.L 0
or
.L R_OK|W_OK
then all configuration parameters are listed.
.L R_OK
lists the readonly configuration parameters and
.L W_OK
lists the settable configuration parameters.
.L X_OK
lists the settable configuration parameters in a form that can be
snarfed for input to the
 getconf (1) command.

.L astcopy
efficiently copies up to
 n bytes from the file descriptor
 rfd to the file descriptor
 wfd . The actual number of bytes copied is returned; -1 is returned on error.
If
 n is 0 then an optimal number of bytes (with respect to both
 rfd and
 wfd ) is copied.

If possible
 mmap (2) is used to do the transfer.
Some implementations may bypass user buffer copies usually required by the
 read (2)- write (2) paradigm.

.L astquery
outputs an
 sfprintf (3) prompt specified by
 "format, .\|.\|." to the controlling terminal and reads a response from the controlling terminal.
Offirmative response returns
.LR 0 ,
.L EOF
or quit response returns
.LR -1 ,
otherwise
.L 1
is returned.
If
 quit is greater than
.L 0
then
 exit(quit) is called on a quit response.
The responses will eventually be locale specific.

.L astwinsize
returns the number of rows in
 *rows and the number of columns
 *col for the terminal file descriptor
 fd . If the number of rows or columns cannot be determined or if
 fd is not a terminal then
 *rows and
 *cols are set to
.LR 0 .
If
 ioctl (2) methods fail then the environment variable
.L LINES
is used to set
 *rows and the environment variable
.L COLUMNS
is used to set
 *cols .  "SEE ALSO"
getconf(1), confstr(2), mmap(2), pathconf(2), read(2), sysconf(2), write(2)