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Updated documentation for dot-locking.

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sperber 2002-01-07 13:23:22 +00:00
parent cf3eb3d822
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doc/scsh-manual/miscprocs.tex
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@ -67,35 +67,59 @@ may generate the lock for a given file.
Here is scsh's interface to dot-locking: Here is scsh's interface to dot-locking:
\defun {obtain-dot-lock} {filename [interval retry-number]} {\boolean} \defun {obtain-dot-lock} {filename [interval retry-number stale-time]} {\boolean}
Tries to obtain the lock for \var{filename}. If the file is already \begin{desc}
locked, the thread sleeps for \var{interval} milliseconds (default is Tries to obtain the lock for \var{filename}. If the file is already
1000) before it retries. If the lock cannot be obtained after locked, the thread sleeps for \var{interval} seconds (default is 1)
\var{retry-number} attempts, the procedure returns \sharpf, otherwise before it retries. If the lock cannot be obtained after
\sharpt. The default value of \var{retry-number} is \sharpf which \var{retry-number} attempts, the procedure returns \sharpf,
corresponds to an infinite number of retires. otherwise \sharpt. The default value of \var{retry-number} is
\sharpf which corresponds to an infinite number of retires.
If \var{stale-time} is non-\sharpf, it specifies the minimum age a
lock may have (in seconds) before it is considered \textit{stale}.
\ex{Obtain-dot-lock} attempts to delete stale locks. If it was
succcessful obtaining a lock after breaking it, \ex{obtain-dot-lock}
returns \ex{broken}. If \var{stale-time} is \sharpf,
\ex{obtain-dot-lock} never considers a lock stale. The default for
\var{stale-time} is 300.
Note that it is possible that \ex{obtain-dot-lock} breaks a lock
but nevertheless fails to obtain it otherwise. If it is necessary
to handle this case specially, use \ex{break-dot-lock} directly
(see below) rather than specifying a non-\sharpf \var{stale-time}
\end{desc}
\defun {break-dot-lock} {filename} {undefined}
\begin{desc}
Breaks the lock for \var{filename} if one exists.
\end{desc}
\defun {release-dot-lock} {filename} {\boolean} \defun {release-dot-lock} {filename} {\boolean}
Releases the lock for \var{filename}. On success, \begin{desc}
\ex{release-dot-lock} returns \sharpt, otherwise \sharpf. Note that Releases the lock for \var{filename}. On success,
this procedure can also be used to break the lock for \var{filename}. \ex{release-dot-lock} returns \sharpt, otherwise \sharpf. Note that
this procedure can also be used to break the lock for
\var{filename}.
\end{desc}
\defun{with-dot-lock*} {filename thunk} {value(s) of thunk} \defun{with-dot-lock*} {filename thunk} {value(s) of thunk}
\dfnx {with-dot-lock} {filename body \ldots} {value(s) of body}{syntax} \dfnx{with-dot-lock} {filename body \ldots} {value(s) of body}{syntax}
This procedure obtains the requested lock, and then calls \begin{desc}
\ex{(\var{thunk})}. When \var{thunk} returns, the lock is released. This procedure obtains the requested lock, and then calls
A non-local exit (\eg, throwing to a saved continuation or raising \ex{(\var{thunk})}. When \var{thunk} returns, the lock is released.
an exception) also causes the lock to be released. A non-local exit (\eg, throwing to a saved continuation or raising
an exception) also causes the lock to be released.
After a normal return from \var{thunk}, its return values are returned
by \ex{with-dot-lock*}. After a normal return from \var{thunk}, its return values are
The \ex{with-dot-lock} special form is equivalent syntactic sugar. returned by \ex{with-dot-lock*}. The \ex{with-dot-lock} special
form is equivalent syntactic sugar.
\end{desc}
\section{Syslog facility} \section{Syslog facility}
\label{syslog-facility} \label{syslog-facility}