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Converted to use semantic markup. This is an example of how many of the new 

constructs should be used.
This commit is contained in:
Fred Drake 1998-01-22 15:56:41 +00:00
parent dd28d57fd0
commit 55f4492859
2 changed files with 78 additions and 72 deletions
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75
Doc/lib/libsignal.tex
View File

@ -11,7 +11,7 @@ Some general rules for working with signals handlers:
A handler for a particular signal, once set, remains installed until A handler for a particular signal, once set, remains installed until
it is explicitly reset (i.e. Python emulates the BSD style interface it is explicitly reset (i.e. Python emulates the BSD style interface
regardless of the underlying implementation), with the exception of regardless of the underlying implementation), with the exception of
the handler for \code{SIGCHLD}, which follows the underlying the handler for \constant{SIGCHLD}, which follows the underlying
implementation. implementation.
\item \item
@ -22,7 +22,7 @@ sections (since this is not supported by all \UNIX{} flavors).
Although Python signal handlers are called asynchronously as far as Although Python signal handlers are called asynchronously as far as
the Python user is concerned, they can only occur between the the Python user is concerned, they can only occur between the
``atomic'' instructions of the Python interpreter. This means that ``atomic'' instructions of the Python interpreter. This means that
signals arriving during long calculations implemented purely in C signals arriving during long calculations implemented purely in \C{}
(e.g.\ regular expression matches on large bodies of text) may be (e.g.\ regular expression matches on large bodies of text) may be
delayed for an arbitrary amount of time. delayed for an arbitrary amount of time.
@ -33,14 +33,14 @@ This is dependent on the underlying \UNIX{} system's semantics regarding
interrupted system calls. interrupted system calls.
\item \item
Because the C signal handler always returns, it makes little sense to Because the \C{} signal handler always returns, it makes little sense to
catch synchronous errors like \code{SIGFPE} or \code{SIGSEGV}. catch synchronous errors like \constant{SIGFPE} or \constant{SIGSEGV}.
\item \item
Python installs a small number of signal handlers by default: Python installs a small number of signal handlers by default:
\code{SIGPIPE} is ignored (so write errors on pipes and sockets can be \constant{SIGPIPE} is ignored (so write errors on pipes and sockets can be
reported as ordinary Python exceptions), \code{SIGINT} is translated reported as ordinary Python exceptions), \constant{SIGINT} is translated
into a \code{KeyboardInterrupt} exception, and \code{SIGTERM} is into a \exception{KeyboardInterrupt} exception, and \constant{SIGTERM} is
caught so that necessary cleanup (especially \code{sys.exitfunc}) can caught so that necessary cleanup (especially \code{sys.exitfunc}) can
be performed before actually terminating. All of these can be be performed before actually terminating. All of these can be
overridden. overridden.
@ -48,25 +48,27 @@ overridden.
\item \item
Some care must be taken if both signals and threads are used in the Some care must be taken if both signals and threads are used in the
same program. The fundamental thing to remember in using signals and same program. The fundamental thing to remember in using signals and
threads simultaneously is:\ always perform \code{signal()} operations threads simultaneously is:\ always perform \function{signal()} operations
in the main thread of execution. Any thread can perform an in the main thread of execution. Any thread can perform an
\code{alarm()}, \code{getsignal()}, or \code{pause()}; only the main \function{alarm()}, \function{getsignal()}, or \function{pause()};
thread can set a new signal handler, and the main thread will be the only the main thread can set a new signal handler, and the main thread
only one to receive signals (this is enforced by the Python signal will be the only one to receive signals (this is enforced by the
module, even if the underlying thread implementation supports sending Python \module{signal} module, even if the underlying thread
signals to individual threads). This means that signals can't be used implementation supports sending signals to individual threads). This
as a means of interthread communication. Use locks instead. means that signals can't be used as a means of interthread
communication. Use locks instead.
\end{itemize} \end{itemize}
The variables defined in the signal module are: The variables defined in the \module{signal} module are:
\renewcommand{\indexsubitem}{(in module signal)} \renewcommand{\indexsubitem}{(in module signal)}
\begin{datadesc}{SIG_DFL} \begin{datadesc}{SIG_DFL}
This is one of two standard signal handling options; it will simply This is one of two standard signal handling options; it will simply
perform the default function for the signal. For example, on most perform the default function for the signal. For example, on most
systems the default action for SIGQUIT is to dump core and exit, systems the default action for \constant{SIGQUIT} is to dump core
while the default action for SIGCLD is to simply ignore it. and exit, while the default action for \constant{SIGCLD} is to
simply ignore it.
\end{datadesc} \end{datadesc}
\begin{datadesc}{SIG_IGN} \begin{datadesc}{SIG_IGN}
@ -76,12 +78,12 @@ The variables defined in the signal module are:
\begin{datadesc}{SIG*} \begin{datadesc}{SIG*}
All the signal numbers are defined symbolically. For example, the All the signal numbers are defined symbolically. For example, the
hangup signal is defined as \code{signal.SIGHUP}; the variable names hangup signal is defined as \constant{signal.SIGHUP}; the variable names
are identical to the names used in C programs, as found in are identical to the names used in C programs, as found in
\file{signal.h}. \file{<signal.h>}.
The \UNIX{} man page for \file{signal} lists the existing signals (on The \UNIX{} man page for `\cfunction{signal()}' lists the existing
some systems this is \file{signal(2)}, on others the list is in signals (on some systems this is \manpage{signal}{2}, on others the
\file{signal(7)}). list is in \manpage{signal}{7}).
Note that not all systems define the same set of signal names; only Note that not all systems define the same set of signal names; only
those names defined by the system are defined by this module. those names defined by the system are defined by this module.
\end{datadesc} \end{datadesc}
@ -90,11 +92,11 @@ The variables defined in the signal module are:
One more than the number of the highest signal number. One more than the number of the highest signal number.
\end{datadesc} \end{datadesc}
The signal module defines the following functions: The \module{signal} module defines the following functions:
\begin{funcdesc}{alarm}{time} \begin{funcdesc}{alarm}{time}
If \var{time} is non-zero, this function requests that a If \var{time} is non-zero, this function requests that a
\code{SIGALRM} signal be sent to the process in \var{time} seconds. \constant{SIGALRM} signal be sent to the process in \var{time} seconds.
Any previously scheduled alarm is canceled (i.e.\ only one alarm can Any previously scheduled alarm is canceled (i.e.\ only one alarm can
be scheduled at any time). The returned value is then the number of be scheduled at any time). The returned value is then the number of
seconds before any previously set alarm was to have been delivered. seconds before any previously set alarm was to have been delivered.
@ -102,36 +104,37 @@ The signal module defines the following functions:
alarm is canceled. The return value is the number of seconds alarm is canceled. The return value is the number of seconds
remaining before a previously scheduled alarm. If the return value remaining before a previously scheduled alarm. If the return value
is zero, no alarm is currently scheduled. (See the \UNIX{} man page is zero, no alarm is currently scheduled. (See the \UNIX{} man page
\code{alarm(2)}.) \manpage{alarm}{2}.)
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{getsignal}{signalnum} \begin{funcdesc}{getsignal}{signalnum}
Return the current signal handler for the signal \var{signalnum}. Return the current signal handler for the signal \var{signalnum}.
The returned value may be a callable Python object, or one of the The returned value may be a callable Python object, or one of the
special values \code{signal.SIG_IGN}, \code{signal.SIG_DFL} or special values \constant{signal.SIG_IGN}, \constant{signal.SIG_DFL} or
\code{None}. Here, \code{signal.SIG_IGN} means that the signal was \constant{None}. Here, \constant{signal.SIG_IGN} means that the
previously ignored, \code{signal.SIG_DFL} means that the default way signal was previously ignored, \constant{signal.SIG_DFL} means that the
of handling the signal was previously in use, and \code{None} means default way of handling the signal was previously in use, and
that the previous signal handler was not installed from Python. \code{None} means that the previous signal handler was not installed
from Python.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{pause}{} \begin{funcdesc}{pause}{}
Cause the process to sleep until a signal is received; the Cause the process to sleep until a signal is received; the
appropriate handler will then be called. Returns nothing. (See the appropriate handler will then be called. Returns nothing. (See the
\UNIX{} man page \code{signal(2)}.) \UNIX{} man page \manpage{signal}{2}.)
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{signal}{signalnum\, handler} \begin{funcdesc}{signal}{signalnum\, handler}
Set the handler for signal \var{signalnum} to the function Set the handler for signal \var{signalnum} to the function
\var{handler}. \var{handler} can be any callable Python object, or \var{handler}. \var{handler} can be any callable Python object, or
one of the special values \code{signal.SIG_IGN} or one of the special values \constant{signal.SIG_IGN} or
\code{signal.SIG_DFL}. The previous signal handler will be returned \constant{signal.SIG_DFL}. The previous signal handler will be returned
(see the description of \code{getsignal()} above). (See the \UNIX{} (see the description of \function{getsignal()} above). (See the
man page \code{signal(2)}.) \UNIX{} man page \manpage{signal}{2}.)
When threads are enabled, this function can only be called from the When threads are enabled, this function can only be called from the
main thread; attempting to call it from other threads will cause a main thread; attempting to call it from other threads will cause a
\code{ValueError} exception to be raised. \exception{ValueError} exception to be raised.
The \var{handler} is called with two arguments: the signal number The \var{handler} is called with two arguments: the signal number
and the current stack frame (\code{None} or a frame object; see the and the current stack frame (\code{None} or a frame object; see the

75
Doc/libsignal.tex
View File

@ -11,7 +11,7 @@ Some general rules for working with signals handlers:
A handler for a particular signal, once set, remains installed until A handler for a particular signal, once set, remains installed until
it is explicitly reset (i.e. Python emulates the BSD style interface it is explicitly reset (i.e. Python emulates the BSD style interface
regardless of the underlying implementation), with the exception of regardless of the underlying implementation), with the exception of
the handler for \code{SIGCHLD}, which follows the underlying the handler for \constant{SIGCHLD}, which follows the underlying
implementation. implementation.
\item \item
@ -22,7 +22,7 @@ sections (since this is not supported by all \UNIX{} flavors).
Although Python signal handlers are called asynchronously as far as Although Python signal handlers are called asynchronously as far as
the Python user is concerned, they can only occur between the the Python user is concerned, they can only occur between the
``atomic'' instructions of the Python interpreter. This means that ``atomic'' instructions of the Python interpreter. This means that
signals arriving during long calculations implemented purely in C signals arriving during long calculations implemented purely in \C{}
(e.g.\ regular expression matches on large bodies of text) may be (e.g.\ regular expression matches on large bodies of text) may be
delayed for an arbitrary amount of time. delayed for an arbitrary amount of time.
@ -33,14 +33,14 @@ This is dependent on the underlying \UNIX{} system's semantics regarding
interrupted system calls. interrupted system calls.
\item \item
Because the C signal handler always returns, it makes little sense to Because the \C{} signal handler always returns, it makes little sense to
catch synchronous errors like \code{SIGFPE} or \code{SIGSEGV}. catch synchronous errors like \constant{SIGFPE} or \constant{SIGSEGV}.
\item \item
Python installs a small number of signal handlers by default: Python installs a small number of signal handlers by default:
\code{SIGPIPE} is ignored (so write errors on pipes and sockets can be \constant{SIGPIPE} is ignored (so write errors on pipes and sockets can be
reported as ordinary Python exceptions), \code{SIGINT} is translated reported as ordinary Python exceptions), \constant{SIGINT} is translated
into a \code{KeyboardInterrupt} exception, and \code{SIGTERM} is into a \exception{KeyboardInterrupt} exception, and \constant{SIGTERM} is
caught so that necessary cleanup (especially \code{sys.exitfunc}) can caught so that necessary cleanup (especially \code{sys.exitfunc}) can
be performed before actually terminating. All of these can be be performed before actually terminating. All of these can be
overridden. overridden.
@ -48,25 +48,27 @@ overridden.
\item \item
Some care must be taken if both signals and threads are used in the Some care must be taken if both signals and threads are used in the
same program. The fundamental thing to remember in using signals and same program. The fundamental thing to remember in using signals and
threads simultaneously is:\ always perform \code{signal()} operations threads simultaneously is:\ always perform \function{signal()} operations
in the main thread of execution. Any thread can perform an in the main thread of execution. Any thread can perform an
\code{alarm()}, \code{getsignal()}, or \code{pause()}; only the main \function{alarm()}, \function{getsignal()}, or \function{pause()};
thread can set a new signal handler, and the main thread will be the only the main thread can set a new signal handler, and the main thread
only one to receive signals (this is enforced by the Python signal will be the only one to receive signals (this is enforced by the
module, even if the underlying thread implementation supports sending Python \module{signal} module, even if the underlying thread
signals to individual threads). This means that signals can't be used implementation supports sending signals to individual threads). This
as a means of interthread communication. Use locks instead. means that signals can't be used as a means of interthread
communication. Use locks instead.
\end{itemize} \end{itemize}
The variables defined in the signal module are: The variables defined in the \module{signal} module are:
\renewcommand{\indexsubitem}{(in module signal)} \renewcommand{\indexsubitem}{(in module signal)}
\begin{datadesc}{SIG_DFL} \begin{datadesc}{SIG_DFL}
This is one of two standard signal handling options; it will simply This is one of two standard signal handling options; it will simply
perform the default function for the signal. For example, on most perform the default function for the signal. For example, on most
systems the default action for SIGQUIT is to dump core and exit, systems the default action for \constant{SIGQUIT} is to dump core
while the default action for SIGCLD is to simply ignore it. and exit, while the default action for \constant{SIGCLD} is to
simply ignore it.
\end{datadesc} \end{datadesc}
\begin{datadesc}{SIG_IGN} \begin{datadesc}{SIG_IGN}
@ -76,12 +78,12 @@ The variables defined in the signal module are:
\begin{datadesc}{SIG*} \begin{datadesc}{SIG*}
All the signal numbers are defined symbolically. For example, the All the signal numbers are defined symbolically. For example, the
hangup signal is defined as \code{signal.SIGHUP}; the variable names hangup signal is defined as \constant{signal.SIGHUP}; the variable names
are identical to the names used in C programs, as found in are identical to the names used in C programs, as found in
\file{signal.h}. \file{<signal.h>}.
The \UNIX{} man page for \file{signal} lists the existing signals (on The \UNIX{} man page for `\cfunction{signal()}' lists the existing
some systems this is \file{signal(2)}, on others the list is in signals (on some systems this is \manpage{signal}{2}, on others the
\file{signal(7)}). list is in \manpage{signal}{7}).
Note that not all systems define the same set of signal names; only Note that not all systems define the same set of signal names; only
those names defined by the system are defined by this module. those names defined by the system are defined by this module.
\end{datadesc} \end{datadesc}
@ -90,11 +92,11 @@ The variables defined in the signal module are:
One more than the number of the highest signal number. One more than the number of the highest signal number.
\end{datadesc} \end{datadesc}
The signal module defines the following functions: The \module{signal} module defines the following functions:
\begin{funcdesc}{alarm}{time} \begin{funcdesc}{alarm}{time}
If \var{time} is non-zero, this function requests that a If \var{time} is non-zero, this function requests that a
\code{SIGALRM} signal be sent to the process in \var{time} seconds. \constant{SIGALRM} signal be sent to the process in \var{time} seconds.
Any previously scheduled alarm is canceled (i.e.\ only one alarm can Any previously scheduled alarm is canceled (i.e.\ only one alarm can
be scheduled at any time). The returned value is then the number of be scheduled at any time). The returned value is then the number of
seconds before any previously set alarm was to have been delivered. seconds before any previously set alarm was to have been delivered.
@ -102,36 +104,37 @@ The signal module defines the following functions:
alarm is canceled. The return value is the number of seconds alarm is canceled. The return value is the number of seconds
remaining before a previously scheduled alarm. If the return value remaining before a previously scheduled alarm. If the return value
is zero, no alarm is currently scheduled. (See the \UNIX{} man page is zero, no alarm is currently scheduled. (See the \UNIX{} man page
\code{alarm(2)}.) \manpage{alarm}{2}.)
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{getsignal}{signalnum} \begin{funcdesc}{getsignal}{signalnum}
Return the current signal handler for the signal \var{signalnum}. Return the current signal handler for the signal \var{signalnum}.
The returned value may be a callable Python object, or one of the The returned value may be a callable Python object, or one of the
special values \code{signal.SIG_IGN}, \code{signal.SIG_DFL} or special values \constant{signal.SIG_IGN}, \constant{signal.SIG_DFL} or
\code{None}. Here, \code{signal.SIG_IGN} means that the signal was \constant{None}. Here, \constant{signal.SIG_IGN} means that the
previously ignored, \code{signal.SIG_DFL} means that the default way signal was previously ignored, \constant{signal.SIG_DFL} means that the
of handling the signal was previously in use, and \code{None} means default way of handling the signal was previously in use, and
that the previous signal handler was not installed from Python. \code{None} means that the previous signal handler was not installed
from Python.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{pause}{} \begin{funcdesc}{pause}{}
Cause the process to sleep until a signal is received; the Cause the process to sleep until a signal is received; the
appropriate handler will then be called. Returns nothing. (See the appropriate handler will then be called. Returns nothing. (See the
\UNIX{} man page \code{signal(2)}.) \UNIX{} man page \manpage{signal}{2}.)
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{signal}{signalnum\, handler} \begin{funcdesc}{signal}{signalnum\, handler}
Set the handler for signal \var{signalnum} to the function Set the handler for signal \var{signalnum} to the function
\var{handler}. \var{handler} can be any callable Python object, or \var{handler}. \var{handler} can be any callable Python object, or
one of the special values \code{signal.SIG_IGN} or one of the special values \constant{signal.SIG_IGN} or
\code{signal.SIG_DFL}. The previous signal handler will be returned \constant{signal.SIG_DFL}. The previous signal handler will be returned
(see the description of \code{getsignal()} above). (See the \UNIX{} (see the description of \function{getsignal()} above). (See the
man page \code{signal(2)}.) \UNIX{} man page \manpage{signal}{2}.)
When threads are enabled, this function can only be called from the When threads are enabled, this function can only be called from the
main thread; attempting to call it from other threads will cause a main thread; attempting to call it from other threads will cause a
\code{ValueError} exception to be raised. \exception{ValueError} exception to be raised.
The \var{handler} is called with two arguments: the signal number The \var{handler} is called with two arguments: the signal number
and the current stack frame (\code{None} or a frame object; see the and the current stack frame (\code{None} or a frame object; see the