inotify
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demo
main program
(**
\brief Sample program showing inotify events.
\version @0x5A4EEB4C
\author Kai Burghardt <wiz at KaiBurghardt.de>
\date 2018
\copyright All rights reserved.
This program prints a readable representation of caught inotify events.
It is non-interactive and does only watch a directory/file specified
at compile-time.
*)
program inotifytst(input, output, stderr);
{$mode objfpc}
{$modeswitch classicprocvars on}
{$typedAddress on}
uses
baseunix, linux, gettext, sysutils;
const
(**
\brief directory/file to be monitored by inotify
\note Not yet at run-time existing files are not treat specially.
This program does not test whether watchedPath is a valid path.
However, inotify does not add watches to non-existing paths.
So inotify_add_watch may raise an error.
*)
watchedPath = '/tmp/abc';
/// \brief holds size of largest expected inotify_event size
maxExpEventSize = sizeof(inotify_event) + name_max;
// resource strings {{{
resourcestring
warning = '⚠: ';
error = '↯: ';
closeInotifyFDfailed = 'closing inotify file descriptor failed';
disassocInwdFrInfdFailed = 'disassociating inwd from infd failed';
initializingInotifyFDfailed =
'initializing inotify file descriptor failed';
addingWatchedPathToInotifyWatchListFailed =
'adding ''%0:s'' to inotify watch list failed';
couldNotAllocateMemForInotifyEvents =
'could not allocate memory for inotify events';
preparingOfSignalHandlerInstallFailed =
'preparing of signal-handler install failed';
couldNotInstallSignalHandlerForSigint =
'could not install signal handler for sigint';
readingFromInotifyFDfailed =
'reading from inotify file descriptor failed';
// end of resourcestring }}}
var
/// \brief inotify file descriptor
infd: cint;
/// \brief inotify watch descriptor
inwd: cint;
/// \brief buffer for reading inotify events
inEventQueueBuffer: PChar;
bytesReadCount, bytesProcessedCount: TsSize;
/// \brief a pointer to handle a single inotify_event
inEvent: PInotify_event;
/// \brief pointer to a signal action record
newAction: PSigActionRec;
(**
\brief Closes inotify file descriptor.
closeInFd closes the inotify file descriptor by invoking fpClose.
It prints a warning on stderr if it went wrong but does not abort.
*)
procedure closeInFD;
begin
// when all fds referring to an inotify-instance have been closed,
// the underlying object and its resources are automatically freed
if fpClose(infd) <> 0 then
begin
writeln(stderr, warning + closeInotifyFDfailed);
end;
end;
(**
\brief Removes inotify watch
cleanUpInWdNFd removes the only installed inotify watch
from (the only) inotify watch descriptor.
*)
procedure cleanUpInWD;
begin
if inotify_rm_watch(infd, inwd) <> 0 then
begin
writeln(stderr, warning + disassocInwdFrInfdFailed);
end;
end;
(**
\brief frees reserved memory
cleanUpEverything frees allocated memory which is reserved for
operations in the main loop.
\sa sigHandler
*)
procedure cleanUpMemory;
begin
freeMem(inEventQueueBuffer, maxExpEventSize);
end;
(**
\brief procedure-wrapper for intended termination by signals
sigHandler calls cleanUpEverything.
It writes a final newline and halts program execution.
*)
procedure sigHandler(
signal: longInt;
info: PSigInfo;
context: PSigContext
); noreturn;
begin
writeln;
halt(0);
end;
(* *)
(* M A I N *)
(* *)
begin
//translateResourcestrings('/usr/share/locale/%s/LC_MESSAGES/' +
// applicationName() + '.mo');
translateResourcestrings(applicationName() + '.%s.mo');
// function inotify_init() initializes a new inotify instance and
// returns a file descriptor associated with its inotify event queue
infd := inotify_init();
if infd < 0 then
begin
writeln(stderr, error + initializingInotifyFDfailed);
// optional: further error analysis with fpgeterrno()
halt(1);
end;
addExitProc(closeInFD);
// next step: adding a watch to a previously initialized inotify instance
inwd := inotify_add_watch(infd, watchedPath, in_all_events);
if inwd < 0 then
begin
writeln(stderr, error +
format(addingWatchedPathToInotifyWatchListFailed, [watchedPath]));
// optional: retrieve errno with fpgeterrno()
halt(2);
end;
addExitProc(cleanUpInWD);
// avoid a run-time error on getMem-failure
returnNilIfGrowHeapFails := true;
// let's occupy some more more heap!
inEventQueueBuffer := getMem(maxExpEventSize);
// check on nil-pointer (failure)
if not assigned(inEventQueueBuffer) then
begin
writeln(stderr, error + couldNotAllocateMemForInotifyEvents);
halt(3);
end;
addExitProc(cleanUpMemory);
// install a signal handler for several signals
new(newAction);
if not assigned(newAction) then
begin
writeln(stderr, error + preparingOfSignalHandlerInstallFailed);
halt(4);
end;
// preparing signal action record
// save address of sigHandler procedure
newAction^.sa_handler := sigActionHandler(@sigHandler);
fillchar(newAction^.sa_mask, sizeof(newAction^.sa_mask), #0);
newAction^.sa_flags := 0;
// pass sigActionRec to sigaction(2) syscall
if fpSigAction(SigHup or SigInt or SigQuit or SigAbrt or SigTerm or
SigTStp, newAction, nil) <> 0 then
begin
writeln(stderr, error + couldNotInstallSignalHandlerForSigint);
halt(5);
end;
// get rid of unused newAction
dispose(newAction);
// TODO: find something better than
// a while-true-loop and signal handling
while true do
begin
// read() returns the amount of bytes have been read.
// read() reads at most maxExpEventSize bytes to the memory position
// specified by inEventQueueBuffer.
// It's only possible to read whole inotify events,
// but no fractions even though
// the _beginning_ of the next event may fit into remaining space.
bytesReadCount := fpRead(infd, inEventQueueBuffer, maxExpEventSize);
if bytesReadCount < 0 then
begin
writeln(stderr, error + readingFromInotifyFDfailed);
halt(6);
end;
// as there may be multiple inotify_events saved at inEventQueueBuffer
// we have to keep a counter how much has been processed
bytesProcessedCount := 0;
// reset inEvent
// typecast PChar to use it as a PInotify_event as such allows the
// usage of dot-fieldname-designators
inEvent := PInotify_event(inEventQueueBuffer);
while bytesProcessedCount < bytesReadCount do
begin
// print a readable representation of current inotify_event
writeln('inotify_event:');
with inEvent^ do
begin
writeln(' wd: ', wd);
writeln(' mask: %', binStr(mask, 32));
// several tests on the mask {{{
if (mask and IN_ACCESS) > 0 then
begin
writeln(' IN_ACCESS');
end;
if (mask and IN_MODIFY) > 0 then
begin
writeln(' IN_MODIFY');
end;
if (mask and IN_ATTRIB) > 0 then
begin
writeln(' IN_ATTRIB');
end;
if (mask and IN_CLOSE_WRITE) > 0 then
begin
writeln(' IN_CLOSE_WRITE');
end;
if (mask and IN_CLOSE_NOWRITE) > 0 then
begin
writeln(' IN_CLOSE_NOWRITE');
end;
if (mask and IN_OPEN) > 0 then
begin
writeln(' IN_OPEN');
end;
if (mask and IN_MOVED_FROM) > 0 then
begin
writeln(' IN_MOVED_FROM');
end;
if (mask and IN_MOVED_TO) > 0 then
begin
writeln(' IN_MOVED_TO');
end;
if (mask and IN_CLOSE) > 0 then
begin
writeln(' IN_CLOSE = ',
'IN_CLOSE_WRITE or IN_CLOSE_NOWRITE');
end;
if (mask and IN_MOVE) > 0 then
begin
writeln(' IN_MOVE = ',
'IN_MOVED_FROM or IN_MOVED_TO');
end;
if (mask and IN_CREATE) > 0 then
begin
writeln(' IN_CREATE');
end;
if (mask and IN_DELETE) > 0 then
begin
writeln(' IN_DELETE');
end;
if (mask and IN_DELETE_SELF) > 0 then
begin
writeln(' IN_DELETE_SELF');
end;
if (mask and IN_MOVE_SELF) > 0 then
begin
writeln(' IN_MOVE_SELF');
end;
if (mask and IN_UNMOUNT) > 0 then
begin
writeln(' IN_UNMOUNT');
end;
if (mask and IN_Q_OVERFLOW) > 0 then
begin
writeln(' IN_Q_OVERFLOW');
end;
if (mask and IN_IGNORED) > 0 then
begin
writeln(' IN_IGNORED');
end;
if (mask and IN_ISDIR) > 0 then
begin
writeln(' IN_ISDIR');
end;
// }}}
writeln(' cookie: $', hexStr(cookie, 8));
// note: len does not contain the actual length of the name but
// also counts any following null-characters needed for well
// address-alignment
writeln(' len: ', len);
// The record's name field has been declared
// to be a /single/ character.
// Indeed we know it is a (dynamic) array of char
// what corresponds to C's null-terminated strings.
// Meanwhile writeln() is capable of
// printing null-terminated strings, too.
// All it needs is the information a given argument is such one.
// Referring to inEvent^.name (single char) does not
// but following typecasted pointer:
writeln(' name: ', PChar(@inEvent^.name));
// end of with-inEvent^-do statement
end;
// inotify(7) says the size of an inotify_event is
// sizeof(inotify_event) + len. but wait! it's a trap!
// it's true for C, but in Pascal you got an off-by-one-error:
// the inotify_event-record already
// includes the first character of the name-field.
inc(bytesProcessedCount, sizeof(inotify_event)-1 + inEvent^.len);
inEvent := PInotify_event(@inEventQueueBuffer[sizeof(inotify_event)-1 +
inEvent^.len]);
// end of while-loop over every read inotify event
end;
// end of main-loop while true
end;
end.
// vim: set tw=78 ts=4 noet bs=eol,start,indent fdm=marker fdc=1:
translations
inotifytst.de.po:
#: inotifytst:warning
msgid "warning: "
msgstr "Warnung: "
#: inotifytst:error
msgid "error: "
msgstr "Fehler: "
#: inotifytst:closeinotifyfdfailed
msgid "closing inotify file descriptor failed"
msgstr "inotify Dateideskriptor schließen fehlgeschlagen"
#: inotifytst:disassocinwdfrinfdfailed
msgid "disassociating inwd from infd failed"
msgstr "Trennung von inwd und infd fehlgeschlagen"
#: inotifytst:initializinginotifyfdfailed
msgid "initializing inotify file descriptor failed"
msgstr "inotify Dateideskritpor initialisiieren fehlgeschlagen"
#: inotifytst:addingwatchedpathtoinotifywatchlistfailed
msgid "adding '%s' to inotify watch list failed"
msgstr "hinzufügen von '%s' zur inotify Beobachtungsliste fehlgeschlagen"
#: inotifytst:couldnotallocatememforinotifyevents
msgid "could not allocate memory for inotify events"
msgstr "konnte kein Speicher für inotify Ereignisse reservieren"
#: inotifytst:preparingofsignalhandlerinstallfailed
msgid "preparing of signal-handler install failed"
msgstr "vorbereiten des Signalbehandlers Installation fehlgeschlagen"
#: inotifytst:couldnotinstallsignalhandlerforsigint
msgid "could not install signal handler for sigint"
msgstr "konnte den Signalbehandler für das Unterbrechungssignal nicht installieren"
#: inotifytst:readingfrominotifyfdfailed
msgid "reading from inotify file descriptor failed"
msgstr "vom inotify Dateideskriptor lesen fehlgeschlagen"
inotifytst.en.po:
#: inotifytst:warning
msgid "warning: "
msgstr "warning: "
#: inotifytst:error
msgid "error: "
msgstr "error: "
#: inotifytst:closeinotifyfdfailed
msgid "closing inotify file descriptor failed"
msgstr "closing inotify file descriptor failed"
#: inotifytst:disassocinwdfrinfdfailed
msgid "disassociating inwd from infd failed"
msgstr "disassociating inwd from infd failed"
#: inotifytst:initializinginotifyfdfailed
msgid "initializing inotify file descriptor failed"
msgstr "initializing inotify file descriptor failed"
#: inotifytst:addingwatchedpathtoinotifywatchlistfailed
msgid "adding '%s' to inotify watch list failed"
msgstr "adding '%s' to inotify watch list failed"
#: inotifytst:couldnotallocatememforinotifyevents
msgid "could not allocate memory for inotify events"
msgstr "could not allocate memory for inotify events"
#: inotifytst:preparingofsignalhandlerinstallfailed
msgid "preparing of signal-handler install failed"
msgstr "preparing of signal-handler install failed"
#: inotifytst:couldnotinstallsignalhandlerforsigint
msgid "could not install signal handler for sigint"
msgstr "could not install signal handler for sigint"
#: inotifytst:readingfrominotifyfdfailed
msgid "reading from inotify file descriptor failed"
msgstr "reading from inotify file descriptor failed"
