daemon program using free pascal
CncWare
(c) Copyright 2000
---------------------------------------------------------------------------
Filename..: daemon.pp
Programmer: Ken J. Wright
Date......: 03/21/2000
Purpose - Program to demonstrate construction of a Linux daemon.
Usage:
1) Compile this program.
2) Run it. You will be immediately returned to a command prompt.
3) Issue the command: ps ax|grep daemon. This will show you the process
id of the program "daemon" that you just ran.
4) Issue the command: tail -f daemon.log. This let's you watch the log file
being filled with the message in the code below. Press Ctrl/c to break
out of the tail command.
5) Issue the command: kill -HUP pid. pid is the process number you saw with
the ps command above. You will see that a new log file has been created.
6) Issue the command: kill -TERM pid. This will stop the daemon. Issuing the
ps command above, you will see that the daemon is no longer running.
-------------------------------<< REVISIONS >>--------------------------------
Ver | Date | Prog | Decription
-------+------------+------+--------------------------------------------------
1.00 | 03/21/2000 | kjw | Initial release.
1.01 | 03/21/2000 | kjw | Forgot to close input, output, & stderr.
------------------------------------------------------------------------------
}
Program Daemon;
uses SysUtils,BaseUnix;
Var
{ vars for daemonizing }
bHup,
bTerm : boolean;
fLog : text;
logname : string;
aOld,
aTerm,
aHup : pSigActionRec;
ps1 : psigset;
sSet : cardinal;
pid : pid_t;
secs : longint;
zerosigs : sigset_t;
hr,mn,sc,sc100 : word;
{ handle SIGHUP & SIGTERM }
procedure DoSig(sig : longint);cdecl;
begin
case sig of
SIGHUP : bHup := true;
SIGTERM : bTerm := true;
end;
end;
{ open the log file }
Procedure NewLog;
Begin
Assign(fLog,logname);
Rewrite(fLog);
Writeln(flog,'Log created at ',formatdatetime('hh:nn:ss',now));
Close(fLog);
End;
Begin
logname := 'daemon.log';
secs := 10;
fpsigemptyset(zerosigs);
{ set global daemon booleans }
bHup := true; { to open log file }
bTerm := false;
{ block all signals except -HUP & -TERM }
sSet := $ffffbffe;
ps1 := @sSet;
fpsigprocmask(sig_block,ps1,nil);
{ setup the signal handlers }
new(aOld);
new(aHup);
new(aTerm);
aTerm^.sa_handler{.sh} := SigactionHandler(@DoSig);
aTerm^.sa_mask := zerosigs;
aTerm^.sa_flags := 0;
{$ifndef BSD} {Linux'ism}
aTerm^.sa_restorer := nil;
{$endif}
aHup^.sa_handler := SigactionHandler(@DoSig);
aHup^.sa_mask := zerosigs;
aHup^.sa_flags := 0;
{$ifndef BSD} {Linux'ism}
aHup^.sa_restorer := nil;
{$endif}
fpSigAction(SIGTERM,aTerm,aOld);
fpSigAction(SIGHUP,aHup,aOld);
{ daemonize }
pid := fpFork;
Case pid of
0 : Begin { we are in the child }
Close(input); { close standard in }
Close(output); { close standard out }
Assign(output,'/dev/null');
ReWrite(output);
Close(stderr); { close standard error }
Assign(stderr,'/dev/null');
ReWrite(stderr);
End;
-1 : secs := 0; { forking error, so run as non-daemon }
Else Halt; { successful fork, so parent dies }
End;
{ begin processing loop }
Repeat
If bHup Then Begin
{$I-}
Close(fLog);
{$I+}
IOResult;
NewLog;
bHup := false;
End;
{----------------------}
{ Do your daemon stuff }
Append(flog);
Writeln(flog,'daemon code activated at ',formatdatetime('hh:nn:ss',now));
Close(fLog);
{ the following output goes to the bit bucket }
Writeln('daemon code activated at ',hr:0,':',mn:0,':',sc:0);
{----------------------}
If bTerm Then
BREAK
Else
{ wait a while }
fpSelect(0,nil,nil,nil,secs*1000);
Until bTerm;
End.
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