terminal.texi

一个C源代码分析器

@comment termios.h
@comment POSIX.1
@vindex B600
@comment termios.h
@comment POSIX.1
@vindex B1200
@comment termios.h
@comment POSIX.1
@vindex B1800
@comment termios.h
@comment POSIX.1
@vindex B2400
@comment termios.h
@comment POSIX.1
@vindex B4800
@comment termios.h
@comment POSIX.1
@vindex B9600
@comment termios.h
@comment POSIX.1
@vindex B19200
@comment termios.h
@comment POSIX.1
@vindex B38400
@smallexample
B0  B50  B75  B110  B134  B150  B200
B300  B600  B1200  B1800  B2400  B4800
B9600  B19200  B38400
@end smallexample

@vindex EXTA
@vindex EXTB
BSD defines two additional speed symbols as aliases: @code{EXTA} is an
alias for @code{B19200} and @code{EXTB} is an alias for @code{B38400}.
These aliases are obsolete.

@node Special Characters
@subsection Special Characters

In canonical input, the terminal driver recognizes a number of special
characters which perform various control functions.  These include the
ERASE character (usually @key{DEL}) for editing input, and other editing
characters.  The INTR character (normally @kbd{C-c}) for sending a
@code{SIGINT} signal, and other signal-raising characters, may be
available in either canonical or noncanonical input mode.  All these
characters are described in this section.

The particular characters used are specified in the @code{c_cc} member
of the @code{struct termios} structure.  This member is an array; each
element specifies the character for a particular role.  Each element has
a symbolic constant that stands for the index of that element---for
example, @code{INTR} is the index of the element that specifies the INTR
character, so storing @code{'='} in @code{@var{termios}.c_cc[INTR]}
specifies @samp{=} as the INTR character.

@vindex _POSIX_VDISABLE
On some systems, you can disable a particular special character function
by specifying the value @code{_POSIX_VDISABLE} for that role.  This
value is unequal to any possible character code.  @xref{Options for
Files}, for more information about how to tell whether the operating
system you are using supports @code{_POSIX_VDISABLE}.

@menu
* Editing Characters::          Special characters that terminate lines and
                                  delete text, and other editing functions.
* Signal Characters::           Special characters that send or raise signals
                                  to or for certain classes of processes.
* Start/Stop Characters::       Special characters that suspend or resume
                                  suspended output.
* Other Special::		Other special characters for BSD systems:
				  they can discard output, and print status.
@end menu

@node Editing Characters
@subsubsection Characters for Input Editing

These special characters are active only in canonical input mode.
@xref{Canonical or Not}.

@comment termios.h
@comment POSIX.1
@deftypevr Macro int VEOF
@cindex EOF character
This is the subscript for the EOF character in the special control
character array.  @code{@var{termios}.c_cc[VEOF]} holds the character
itself.

The EOF character is recognized only in canonical input mode.  It acts
as a line terminator in the same way as a newline character, but if the
EOF character is typed at the beginning of a line it causes @code{read}
to return a byte count of zero, indicating end-of-file.  The EOF
character itself is discarded.

Usually, the EOF character is @kbd{C-d}.
@end deftypevr

@comment termios.h
@comment POSIX.1
@deftypevr Macro int VEOL
@cindex EOL character
This is the subscript for the EOL character in the special control
character array.  @code{@var{termios}.c_cc[VEOL]} holds the character
itself.

The EOL character is recognized only in canonical input mode.  It acts
as a line terminator, just like a newline character.  The EOL character
is not discarded; it is read as the last character in the input line.

@c !!! example: this is set to ESC by 4.3 csh with "set filec" so it can
@c complete partial lines without using cbreak or raw mode.

You don't need to use the EOL character to make @key{RET} end a line.
Just set the ICRNL flag.  In fact, this is the default state of
affairs.
@end deftypevr

@comment termios.h
@comment BSD
@deftypevr Macro int VEOL2
@cindex EOL2 character
This is the subscript for the EOL2 character in the special control
character array.  @code{@var{termios}.c_cc[VEOL2]} holds the character
itself.

The EOL2 character works just like the EOL character (see above), but it
can be a different character.  Thus, you can specify two characters to
terminate an input line, by setting EOL to one of them and EOL2 to the
other.

The EOL2 character is a BSD extension; it exists only on BSD systems
and the GNU system.
@end deftypevr

@comment termios.h
@comment POSIX.1
@deftypevr Macro int VERASE
@cindex ERASE character
This is the subscript for the ERASE character in the special control
character array.  @code{@var{termios}.c_cc[VERASE]} holds the
character itself.

The ERASE character is recognized only in canonical input mode.  When
the user types the erase character, the previous character typed is
discarded.  (If the terminal generates multibyte character sequences,
this may cause more than one byte of input to be discarded.)  This
cannot be used to erase past the beginning of the current line of text.
The ERASE character itself is discarded.
@c !!! mention ECHOE here

Usually, the ERASE character is @key{DEL}.
@end deftypevr

@comment termios.h
@comment BSD
@deftypevr Macro int VWERASE
@cindex WERASE character
This is the subscript for the WERASE character in the special control
character array.  @code{@var{termios}.c_cc[VWERASE]} holds the character
itself.

The WERASE character is recognized only in canonical mode.  It erases an
entire word of prior input, and any whitespace after it; whitespace
characters before the word are not erased.

The definition of a ``word'' depends on the setting of the
@code{ALTWERASE} mode; @pxref{Local Modes}.

If the @code{ALTWERASE} mode is not set, a word is defined as a sequence
of any characters except space or tab.

If the @code{ALTWERASE} mode is set, a word is defined as a sequence of
characters containing only letters, numbers, and underscores, optionally
followed by one character that is not a letter, number, or underscore.

The WERASE character is usually @kbd{C-w}.

This is a BSD extension.
@end deftypevr

@comment termios.h
@comment POSIX.1
@deftypevr Macro int VKILL
@cindex KILL character
This is the subscript for the KILL character in the special control
character array.  @code{@var{termios}.c_cc[VKILL]} holds the character
itself.

The KILL character is recognized only in canonical input mode.  When the
user types the kill character, the entire contents of the current line
of input are discarded.  The kill character itself is discarded too.

The KILL character is usually @kbd{C-u}.
@end deftypevr

@comment termios.h
@comment BSD
@deftypevr Macro int VREPRINT
@cindex REPRINT character
This is the subscript for the REPRINT character in the special control
character array.  @code{@var{termios}.c_cc[VREPRINT]} holds the character
itself.

The REPRINT character is recognized only in canonical mode.  It reprints
the current input line.  If some asynchronous output has come while you
are typing, this lets you see the line you are typing clearly again.

The REPRINT character is usually @kbd{C-r}.

This is a BSD extension.
@end deftypevr

@node Signal Characters
@subsubsection Characters that Cause Signals

These special characters may be active in either canonical or noncanonical
input mode, but only when the @code{ISIG} flag is set (@pxref{Local
Modes}).

@comment termios.h
@comment POSIX.1
@deftypevr Macro int VINTR
@cindex INTR character
@cindex interrupt character
This is the subscript for the INTR character in the special control
character array.  @code{@var{termios}.c_cc[VINTR]} holds the character
itself.

The INTR (interrupt) character raises a @code{SIGINT} signal for all
processes in the foreground job associated with the terminal.  The INTR
character itself is then discarded.  @xref{Signal Handling}, for more
information about signals.

Typically, the INTR character is @kbd{C-c}.
@end deftypevr

@comment termios.h
@comment POSIX.1
@deftypevr Macro int VQUIT
@cindex QUIT character
This is the subscript for the QUIT character in the special control
character array.  @code{@var{termios}.c_cc[VQUIT]} holds the character
itself.

The QUIT character raises a @code{SIGQUIT} signal for all processes in
the foreground job associated with the terminal.  The QUIT character
itself is then discarded.  @xref{Signal Handling}, for more information
about signals.

Typically, the QUIT character is @kbd{C-\}.
@end deftypevr

@comment termios.h
@comment POSIX.1
@deftypevr Macro int VSUSP
@cindex SUSP character
@cindex suspend character
This is the subscript for the SUSP character in the special control
character array.  @code{@var{termios}.c_cc[VSUSP]} holds the character
itself.

The SUSP (suspend) character is recognized only if the implementation
supports job control (@pxref{Job Control}).  It causes a @code{SIGTSTP}
signal to be sent to all processes in the foreground job associated with
the terminal.  The SUSP character itself is then discarded.
@xref{Signal Handling}, for more information about signals.

Typically, the SUSP character is @kbd{C-z}.
@end deftypevr

Few applications disable the normal interpretation of the SUSP
character.  If your program does this, it should provide some other
mechanism for the user to stop the job.  When the user invokes this
mechanism, the program should send a @code{SIGTSTP} signal to the
process group of the process, not just to the process itself.
@xref{Signaling Another Process}.

@comment termios.h
@comment BSD
@deftypevr Macro int VDSUSP
@cindex DSUSP character
@cindex delayed suspend character
This is the subscript for the DSUSP character in the special control
character array.  @code{@var{termios}.c_cc[VDSUSP]} holds the character
itself.

The DSUSP (suspend) character is recognized only if the implementation
supports job control (@pxref{Job Control}).  It sends a @code{SIGTSTP}
signal, like the SUSP character, but not right away---only when the
program tries to read it as input.  Not all systems with job control
support DSUSP; only BSD-compatible systems (including the GNU system).

@xref{Signal Handling}, for more information about signals.

Typically, the DSUSP character is @kbd{C-y}.
@end deftypevr

@node Start/Stop Characters
@subsubsection Special Characters for Flow Control

These special characters may be active in either canonical or noncanonical
input mode, but their use is controlled by the flags @code{IXON} and
@code{IXOFF} (@pxref{Input Modes}).

@comment termios.h
@comment POSIX.1
@deftypevr Macro int VSTART
@cindex START character
This is the subscript for the START character in the special control
character array.  @code{@var{termios}.c_cc[VSTART]} holds the
character itself.

The START character is used to support the @code{IXON} and @code{IXOFF}
input modes.  If @code{IXON} is set, receiving a START character resumes
suspended output; the START character itself is discarded.  If
@code{IXANY} is set, receiving any character at all resumes suspended
output; the resuming character is not discarded unless it is the START
character.  @code{IXOFF} is set, the system may also transmit START
characters to the terminal.

The usual value for the START character is @kbd{C-q}.  You may not be
able to change this value---the hardware may insist on using @kbd{C-q}
regardless of what you specify.
@end deftypevr

@comment termios.h
@comment POSIX.1
@deftypevr Macro int VSTOP
@cindex STOP character
This is the subscript for the STOP character in the special control
character array.  @code{@var{termios}.c_cc[VSTOP]} holds the character
itself.

The STOP character is used to support the @code{IXON} and @code{IXOFF}
input modes.  If @code{IXON} is set, receiving a STOP character causes
output to be suspended; the STOP character itself is discarded.  If
@code{IXOFF} is set, the system may also transmit STOP characters to the
terminal, to prevent the input queue from overflowing.

The usual value for the STOP character is @kbd{C-s}.  You may not be
able to change this value---the hardware may insist on using @kbd{C-s}
regardless of what you specify.
@end deftypevr

@node Other Special
@subsubsection Other Special Characters

These special characters exist only in BSD systems and the GNU system.

@comment termios.h
@comment BSD
@deftypevr Macro int VLNEXT
@cindex LNEXT character
This is the subscript for the LNEXT character in the special control
character array.  @code{@var{termios}.c_cc[VLNEXT]} holds the character
itself.

The LNEXT character is recognized only when @code{IEXTEN} is set, but in
both canonical and noncanonical mode.  It disables any special