kyanh wrote:
A`, /me ko^ mong cho+` ca^u tra? lo+`i the^' na`y :(( Bo+?i vi`, /me ddang
vie^'t Winefish ( http://winefish.sf.net ) -- chu+o+ng tri`nh ddo^i khi go.i
chu+o+ng tri`nh ngoa`i va` ddo^i khi pha?i "KILL" (force) chu+o+ng tri`nh
ngoa`i ddo'. Tu'm la.i, Winefish pha?i qua?n ly' ID ca'c chu+o+ng tri`nh con
no' go.i. Bi chu+` ba'c no'i nhu+ the^', thi`i /me so+. qua', lo+~ khi na`o
gie^'t nha^`m thi` ...
/me theo do~i ca'ch la`m cu?a nhie^`u program. Tha^'y no' cu~ng ko^ co' ca'ch
xu+? ly' na`o dda(.c bie^.t. Du+o+'i dda^y la` ca'ch em la`m....
A`, co' pha?i du`ng "fork()" se~ gia?i qhuyeest ddu+o+jc mo.i chuye^.n ko^?
,----
| /* fork():
| create a child proccess the differs
| from the parent only in its PID and PPID;
| the resouce ultilisation are set to 0 */
`----
[code]
/* Taken from SciTTEGTK.cxx
kyanh: everything emitted from `running' will be captured [ 2>&1 ]
*/
static gint xsystem( const gchar *command, const gchar *outfile )
{
gint pid = 0;
/* fork():
create a child proccess the differs from the parent only in its PID and PPID;
the resouce ultilisation are set to 0 */
if ( ( pid = fork() ) == 0 ) {
close( 0 );
gint fh = open( outfile, O_WRONLY );
close( 1 );
dup( fh );
close( 2 );
dup( fh );
DEBUG_MSG( "xsystem: running now [%s]\n", command );
execlp( "/bin/sh", "sh", "-c", command, NULL );
exit( 127 );
}
return pid;
}
[/code]
Du`ng fork() nhu+ ha`m xsystem cu?a kyanh la` o^?n ro^`i, gia' tri. tra?
ve^` cu?a ha`m xsystem tre^n la` pid cu?a child process. Kyanh cu+' go.i
kill pid na`y la` ddu+o+.c.
Gia?i thi'ch:
Fork la` ha`m go.i mo^.t la^`n nhu+ng tra? ve^` hai la^`n. Mo^.t la^`
o+? parent process va` 1 la^`n o+? child process (gia' tri. tra? ve^` -1
co' nghi~a la` lo^~i khi go.i ha`m fork)
---->-Parent Process---->pid = fork() |---------> parent process
ne^'u pid >0
|--------->child process ne^'u pid =0
Tie^'p theo, khi kyanh go.i ha`m execlp trong child process (pid = 0)
thi` image process trong bo^. nho+' cu?a child process *bi. thay the^'*
hoa`n toa`n bo+?i image cu?a chu+o+ng tri`nh ddu+o+.c go.i bo+?i ha`m
excelp, nhu+ng process id kho^ng thay ddo^?i (xem man page cua? ha`m
excelp). Do ddo' chu+o+ng tri`nh ddu+o+.c go.i bo+?i ha`m excelp va^~n
la` con cu?a parent process.
Khi child process ke^'t thu'c, va^~n co`n tho^ng tin ve^` process
trong bo^. nho+' (process id ... gia' tri. tra? ve^` cu?a child process)
=>child tro+? tha`nh zombie process *cho dde^'n khi* parent process
go.i ha`m wait dde^? gia?i pho'ng.
Nhu+ va^.y, kyanh co' the^? handle hoa`n toa`n chu+o+ng tri`nh ddu+o+.c
go.i bo+?i ha`m excelp, go.i kill ma` kho^ng so+. kill nha^`m sang
process kha'c (sau khi go.i ha`m kill ne^n go.i wait dde^? cho+` process
ke^'t thu'c). Kyanh cu~ng co' the^? la`m mo^.t so^' bu+o+'c dde^? kie^?m
tra child process cu?a mi`nh co`n cha.y hay kho^ng (ba(`ng ca'ch go.i
ha`m kill vo+'i signal = 0). Ngoa`i ra kyanh ne^n cha(.n signal
SGN_CHILD dde^? bie^'t khi na`o thi` child process cu?a mi`nh ke^'t thu'c.
Ky~ thua^.t ma` /me du`ng la` cha(.n signal SGN_CHILD, trong ha`m xu+?
li' signal na`y, go.i ha`m wait dde^? cho+` child process exit.
The^m: Ne^'u parent process ke^'t thu'c tru+o+'c child process thi`
child process se~ co' parent process la` 1- init process, va` init
process se~ gia?i pho'ng tho^ng tin ve^` child process khi child process
ke^'t thu'c => gia?i pho'ng process id cho tie^'n tri`nh kha'c.
[OT]
va(n vo+'i cha? vo+?, do+? qua' pha?i kho^ng ca'c ba'c? :(
[/OT]
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