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(Default Ports): Describe buffering on standard ports.

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This commit is contained in:
Kevin Ryde 2005-04-29 23:45:11 +00:00
parent 97d790b384
commit 3fa0a042ba
1 changed files with 29 additions and 7 deletions
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36
doc/ref/api-io.texi
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@ -616,8 +616,19 @@ return 0 immediately if the request size is 0 bytes.
@deffnx {C Function} scm_current_input_port ()
@cindex standard input
Return the current input port. This is the default port used
by many input procedures. Initially, @code{current-input-port}
returns the @dfn{standard input} in Unix and C terminology.
by many input procedures.
Initially this is the @dfn{standard input} in Unix and C terminology.
When the standard input is a tty the port is unbuffered, otherwise
it's fully buffered.
Unbuffered input is good if an application runs an interactive
subprocess, since any type-ahead input won't go into Guile's buffer
and hence be unavailable to the subprocess.
Note that Guile buffering is completely separate from the tty ``line
discipline''. In the usual cooked mode on a tty, Guile only sees a
line of input once the user presses @key{return}.
@end deffn
@rnindex current-output-port
@ -625,16 +636,27 @@ returns the @dfn{standard input} in Unix and C terminology.
@deffnx {C Function} scm_current_output_port ()
@cindex standard output
Return the current output port. This is the default port used
by many output procedures. Initially,
@code{current-output-port} returns the @dfn{standard output} in
Unix and C terminology.
by many output procedures.
Initially this is the @dfn{standard output} in Unix and C terminology.
When the standard output is a tty this port is unbuffered, otherwise
it's fully buffered.
Unbuffered output to a tty is good for ensuring progress output or a
prompt is seen. But an application which always prints whole lines
could change to line buffered, or an application with a lot of output
could go fully buffered and perhaps make explicit @code{force-output}
calls (@pxref{Writing}) at selected points.
@end deffn
@deffn {Scheme Procedure} current-error-port
@deffnx {C Function} scm_current_error_port ()
@cindex standard error output
Return the port to which errors and warnings should be sent (the
@dfn{standard error} in Unix and C terminology).
Return the port to which errors and warnings should be sent.
Initially this is the @dfn{standard error} in Unix and C terminology.
When the standard error is a tty this port is unbuffered, otherwise
it's fully buffered.
@end deffn
@deffn {Scheme Procedure} set-current-input-port port