pid = fork();
ÔÚ´Óϵͳµ÷Óà fork Öзµ»Øʱ£¬Á½¸ö½ø³Ì³ýÁË·µ»ØÖµ pid ²»Í¬Í⣬¾ßÓÐ ÍêÈ«Ò»ÑùµÄÓû§¼¶ÉÏÏÂÎÄ¡£ÔÚ×Ó½ø³ÌÖУ¬pid µÄֵΪÁã¡£ÔÚϵͳÆô¶¯Ê±ÓɺËÐÄÄÚ ²¿µØ´´½¨µÄ½ø³Ì0ÊÇΨһ²»Í¨¹ýϵͳµ÷Óà fork ¶ø´´½¨µÄ½ø³Ì¡£
ºËÐÄΪϵͳµ÷Óà fork Íê³ÉÏÂÁвÙ×÷£º
1. Ϊнø³ÌÔÚ½ø³Ì±íÖзÖÅäÒ»¸ö¿ÕÏî¡£
2. Ϊ×Ó½ø³Ì¸³Ò»¸öΨһµÄ½ø³Ì±êʶºÅ (PID)¡£
3. ×öÒ»¸ö¸¸½ø³ÌÉÏÏÂÎĵÄÂß¼¸±±¾¡£ÓÉÓÚ½ø³ÌµÄijЩ²¿·Ö£¬ÈçÕýÎÄÇø£¬¿ÉÄܱ»¼¸¸ö ½ø³ÌËù¹²Ïí£¬ËùÒÔºËÐÄÓÐʱֻҪÔö¼Óij¸öÇøµÄÒýÓÃÊý¼´¿É£¬¶ø²»ÊÇÕæµÄ½«¸ÃÇø¿½±´µ½Ò»¸ö еÄÄÚ´æÎïÀíÇø¡£
4. Ôö¼ÓÓë¸Ã½ø³ÌÏà¹ØÁªµÄÎļþ±íºÍË÷Òý½Úµã±íµÄÒýÓÃÊý¡£
5. ¶Ô¸¸½ø³Ì·µ»Ø×Ó½ø³ÌµÄ½ø³ÌºÅ£¬¶Ô×Ó½ø³Ì·µ»ØÁã¡£
Àí½âϵͳµ÷Óà fork µÄʵÏÖÊÇÊ®·ÖÖØÒªµÄ£¬ÒòΪ×Ó½ø³Ì¾ÍÏó´ÓÌì¶ø½µÒ»ÑùµØ¿ªÊ¼ ËüµÄÖ´ÐÐÐòÁС£
ÏÂÃæÊÇϵͳµ÷Óà fork µÄËã·¨¡£ºËÐÄÊ×ÏÈÈ·ÐÅÓÐ×ã¹»µÄ×ÊÔ´À´³É¹¦Íê³É fork¡£ Èç¹û×ÊÔ´²»Âú×ãÒªÇó£¬Ôòϵͳµ÷Óà fork ʧ°Ü¡£Èç¹û×ÊÔ´Âú×ãÒªÇ󣬺ËÐÄÔÚ½ø³Ì ±íÖÐÕÒÒ»¸ö¿ÕÏ²¢¿ªÊ¼¹¹Ôì×Ó½ø³ÌµÄÉÏÏÂÎÄ¡£
ÒýÓÃ:Ëã·¨£ºfork
ÊäÈ룺ÎÞ
Êä³ö£º¶Ô¸¸½ø³ÌÊÇ×Ó½ø³ÌµÄ PID
¶Ô×Ó½ø³ÌÊÇ0
{
¼ì²é¿ÉÓõĺËÐÄ×ÊÔ´
È¡Ò»¸ö¿ÕÏеĽø³Ì±íÏîºÍΨһµÄ PID ºÅ
¼ì²éÓû§Ã»Óйý¶àµÄÔËÐнø³Ì
½«×Ó½ø³ÌµÄ״̬ÉèÖÃΪ¡°´´½¨¡±×´Ì¬
½«¸¸½ø³ÌµÄ½ø³Ì±íÖеÄÊý¾Ý¿½±´µ½×Ó½ø³Ì±íÖÐ
µ±Ç°Ä¿Â¼µÄË÷Òý½ÚµãºÍ¸Ä±äµÄ¸ùĿ¼(Èç¹û¿ÉÒÔ)µÄÒýÓÃÊý¼Ó1
Îļþ±íÖеĴò¿ªÎļþµÄÒýÓÃÊý¼Ó1
ÔÚÄÚ´æÖÐ×÷¸¸½ø³ÌÉÏÏÂÎĵĿ½±´
ÔÚ×Ó½ø³ÌµÄϵͳ¼¶ÉÏÏÂÎÄÖÐѹÈëÐéÉèϵͳ¼¶ÉÏÏÂÎIJã
/* ÐéÉèÉÏÏÂÎIJãÖк¬ÓÐʹ×Ó½ø³ÌÄÜ
* ʶ±ð×Ô¼ºµÄÊý¾Ý£¬²¢Ê¹×Ó½ø³Ì±»µ÷¶Èʱ
* ´ÓÕâÀ↑ʼÔËÐÐ
*/
if (ÕýÔÚÖ´ÐеĽø³ÌÊǸ¸½ø³Ì) {
½«×Ó½ø³ÌµÄ״̬ÉèÖÃΪ¡°¾ÍÐ÷¡±×´Ì¬
return (×Ó½ø³ÌµÄ PID) // ´Óϵͳµ½Óû§
}
else {
³õʼ»¯¼ÆʱÇø
return 0;
}
}
ÎÒÃÇÀ´¿´¿´ÏÂÃæµÄÀý×Ó¡£¸Ã³ÌÐò˵Ã÷µÄÊǾ¹ýϵͳµ÷Óà fork Ö®ºó£¬¶ÔÎļþµÄ ¹²Ïí´æÈ¡¡£Óû§µ÷ÓøóÌÐòʱӦÓÐÁ½¸ö²ÎÊý£¬Ò»¸öÊÇÒѾÓеÄÎļþÃû£¬ÁíÍâÒ»¸öÊÇÒª ´´½¨µÄÐÂÎļþÃû¡£¸Ã½ø³Ì´ò¿ªÒÑÓеÄÎļþ£¬´´½¨Ò»¸öÐÂÎļþ£¬È»ºó£¬¼Ù¶¨Ã»ÓÐÓö¼û¹ý ´íÎó£¬Ëüµ÷Óà fork À´´´½¨Ò»¸ö×Ó½ø³Ì¡£×Ó½ø³Ì¿ÉÒÔͨ¹ýʹÓÃÏàͬµÄÎļþÃèÊö ·û¶ø¼Ì³ÐµØ´æÈ¡¸¸½ø³ÌµÄÎļþ(¼´¸¸½ø³ÌÒѾ´ò¿ªºÍ´´½¨µÄÎļþ)¡£
µ±È»£¬¸¸½ø³ÌºÍ×Ó½ø³ÌÒª·Ö±ð¶ÀÁ¢µØµ÷Óà rdwrt º¯Êý£¬²¢Ö´ÐÐÒ»¸öÑ»·£¬¼´´Ó Ô´ÎļþÖжÁÒ»¸ö×Ö½Ú£¬È»ºóдһ¸ö×Ö½Úµ½Ä¿±êÎļþÖÐÇø¡£µ±ÏµÍ³µ÷Óà read Óö¼û Îļþβʱ£¬º¯Êý rdwrt Á¢¼´·µ»Ø¡£[code]#include
int fdrd, fdwt;
char c;
main(int argc, char *argv[])
{
if (argc != 3) {
exit(1);
}
if ((fdrd = open(argv[1], O_RDONLY)) == -1) {
exit(1);
}
if ((fdwt = creat(argv[2], 0666)) == -1) {
exit(1);
}
fork();
// Á½¸ö½ø³ÌÖ´ÐÐͬÑùµÄ´úÂë
rdwrt();
exit(0);
}
rdwrt()
{
for (;;) {
if (read(fdrd, &c, 1) != 1) {
return ;
}
write(fdwt, &c, 1);
}
}[/code]ÔÚÕâ¸öÀý×ÓÖУ¬Á½¸ö½ø³ÌµÄÎļþÃèÊö·û¶¼Ö¸ÏòÏàͬµÄÎļþ±íÏî¡£ÕâÁ½¸ö½ø³ÌÓÀÔ¶ ²»»á¶Á»òдµ½ÏàͬµÄÎļþÆ«ÒÆÁ¿£¬ÒòΪºËÐÄÔÚÿ´Î read ºÍ write µ÷Óà ֮ºó£¬¶¼ÒªÔö¼ÓÎļþµÄÆ«ÒÆÁ¿¡£¾¡¹ÜÁ½¸ö½ø³ÌËƺõÊǽ«Ô´Îļþ¿½±´ÁËÁ½´Î£¬µ«ÒòΪ ËûÃÇ·Öµ£Á˹¤×÷ÈÎÎñ£¬Òò´Ë£¬Ä¿±êÎļþµÄÄÚÈÝÒÀÀµÓÚºËÐĵ÷¶ÈÁ½¸ö½ø³ÌµÄ´ÎÐò¡£Èç¹û ºËÐÄÕâÑùµ÷¶ÈÁ½¸ö½ø³Ì£ºÊ¹ËûÃǽ»ÌæµØÖ´ÐÐËûÃǵÄϵͳµ÷Ó㬻òÉõÖÁʹËûÃǽ»ÌæµØ Ö´ÐÐÿ¶Ô read ºÍ write µ÷Óã¬ÔòÄ¿±êÎļþµÄÄÚÈݺÍÔ´ÎļþµÄÄÚÈÝÍêÈ«Ò»Ö¡£µ«¿¼ÂÇ ÕâÑùµÄÇé¿ö£ºÁ½¸ö½ø³ÌÕýÒª¶ÁÔ´ÎļþÖеÄÁ½¸öÁ¬ÐøµÄ×Ö·û "ab"¡£¼Ù¶¨¸¸½ø³Ì¶ÁÁË×Ö ·û "a"£¬Õâʱ£¬ºËÐÄÔÚ¸¸½ø³Ìд֮ǰ£¬×öÁËÉÏÏÂÎÄÇл»À´Ö´ÐÐ×Ó½ø³Ì¡£Èç¹û×Ó½ø³Ì ¶Áµ½×Ö·û "b"£¬²¢ÔÚ¸¸½ø³Ì±»µ÷¶ÈÇ°£¬½«Ëüдµ½Ä¿±êÎļþ£¬ÄÇôĿ±êÎļþ½«²»ÔÙº¬ÓÐ ×Ö·û´® "ab"£¬¶øÊǺ¬ÓÐ "ba"ÁË¡£ºËÐIJ¢²»±£Ö¤½ø³ÌÖ´ÐеÄÏà¶ÔËÙÂÊ¡£
ÔÙÀ´¿´¿´ÁíÍâÒ»¸öÀý×Ó£º[code]#include
char string[] = "Hello, world";
main()
{
int count, i;
int to_par[2], to_chil[2]; // µ½¸¸¡¢×Ó½ø³ÌµÄ¹ÜµÀ
char buf[256];
pipe(to_par);
pipe(to_chil);
if (fork() == 0) {
// ×Ó½ø³ÌÔÚ´ËÖ´ÐÐ
close(0); // ¹Ø±ÕÀϵıê×¼ÊäÈë
dup(to_child[0]); // ½«¹ÜµÀµÄ¶Á¸´ÖƵ½±ê×¼ÊäÈë
close(1); // ¹Ø±ÕÀϵıê×¼Êä³ö
dup(to_par[1]); // ½«¹ÜµÀµÄд¸´ÖƵ½±ê×¼Êä³ö
close(to_par[1]); // ¹Ø±Õ²»±ØÒªµÄ¹ÜµÀÃèÊö·û
close(to_chil[0]);
close(to_par[0]);
close(to_chil[1]);
for (;;) {
if ((count = read(0, buf, sizeof(buf)) == 0)
exit();
write(1, buf, count);
}
}
// ¸¸½ø³ÌÔÚ´ËÖ´ÐÐ
close(1); // ÖØÐÂÉèÖñê×¼ÊäÈë¡¢Êä³ö
dup(to_chil[1]);
close(0);
dup(to_par[0]);
close(to_chil[1]);
close(to_par[0]);
close(to_chil[0]);
close(to_par[1]);
for (i = 0; i < 15; i++) {
write(1, string, strlen(string));
read(0, buf, sizeof(buf));
}
}[/code]×Ó½ø³Ì´Ó¸¸½ø³Ì¼Ì³ÐÁËÎļþÃèÊö·û0ºÍ1(±ê×¼ÊäÈëºÍ±ê×¼Êä³ö)¡£Á½´ÎÖ´ÐÐϵͳµ÷Óà pipe ·Ö±ðÔÚÊý×é to_par ºÍ to_chil ÖзÖÅäÁËÁ½¸öÎļþÃèÊö·û¡£È»ºó¸Ã½ø³Ì Ö´ÐÐϵͳµ÷Óà fork£¬²¢¸´Öƽø³ÌÉÏÏÂÎÄ£ºÏóÇ°Ò»¸öÀý×ÓÒ»Ñù£¬Ã¿¸ö½ø³Ì´æÈ¡ ×Ô¼ºµÄ˽ÓÐÊý¾Ý¡£¸¸½ø³Ì¹Ø±ÕËûµÄ±ê×¼Êä³öÎļþ(ÎļþÃèÊö·û1)£¬²¢¸´ÖÆ(dup)´Ó¹ÜµÀ Ïß to_chil ·µ»ØµÄдÎļþÃèÊö·û¡£ÒòΪÔÚ¸¸½ø³ÌÎļþÃèÊö·û±íÖеĵÚÒ»¸ö¿Õ²ÛÊÇ¸Õ¸Õ ÓɹرÕÌÚ³öÀ´µÄ£¬ËùÒÔºËÐĽ«¹ÜµÀÏßдÎļþÃèÊö·û¸´ÖƵ½ÁËÎļþÃèÊö·û±íÖеĵÚÒ» ÏîÖУ¬ÕâÑù£¬±ê×¼Êä³öÎļþÃèÊö·û±ä³ÉÁ˹ܵÀÏß to_chil µÄдÎļþÃèÊö·û¡£ ¸¸½ø³ÌÒÔÀàËƵIJÙ×÷½«±ê×¼ÊäÈëÎļþÃèÊö·ûÌ滻Ϊ¹ÜµÀÏß to_par µÄ¶ÁÎļþ ÃèÊö·û¡£Óë´ËÀàËÆ£¬×Ó½ø³Ì¹Ø±ÕËûµÄ±ê×¼ÊäÈëÎļþ(ÎļþÃèÊö·û0)£¬È»ºó¸´ÖÆ (dup) ¹ÜµÀ Ïß to_chil µÄ¶ÁÎļþÃèÊö·û¡£ÓÉÓÚÎļþÃèÊö·û±íµÄµÚÒ»¸ö¿ÕÏîÊÇÔÏȵıê×¼ ÊäÈëÏËùÒÔ×Ó½ø³ÌµÄ±ê×¼ÊäÈë±ä³ÉÁ˹ܵÀÏß to_chil µÄ¶ÁÎļþÃèÊö·û¡£ ×Ó½ø³Ì×öÒ»×éÀàËƵIJÙ×÷ʹËûµÄ±ê×¼Êä³ö±ä³É¹ÜµÀÏß to_par µÄдÎļþÃèÊö ·û¡£È»ºóÁ½¸ö½ø³Ì¹Ø±Õ´Ó pipe ·µ»ØµÄÎļþÃèÊö·û¡£ÉÏÊö²Ù×÷µÄ½á¹ûÊÇ£ºµ± ¸¸½ø³ÌÏò±ê×¼Êä³ö䶫Î÷µÄʱºò£¬Ëûʵ¼ÊÉÏÊÇдÏò to_chil--Ïò×Ó½ø³Ì·¢ËÍ Êý¾Ý£¬¶ø×Ó½ø³ÌÔò´ÓËûµÄ±ê×¼ÊäÈë¶Á¹ÜµÀÏß¡£µ±×Ó½ø³ÌÏòËûµÄ±ê×¼Êä³öдµÄʱºò£¬ Ëûʵ¼ÊÉÏÊÇдÈë to_par--Ïò¸¸½ø³Ì·¢ËÍÊý¾Ý£¬¶ø¸¸½ø³ÌÔò´ÓËûµÄ±ê×¼ÊäÈë ½ÓÊÕÀ´×ԹܵÀÏßµÄÊý¾Ý¡£Á½¸ö½ø³Ìͨ¹ýÁ½Ìõ¹ÜµÀÏß½»»»ÏûÏ¢¡£
ÎÞÂÛÁ½¸ö½ø³ÌÖ´ÐеÄ˳ÐòÈçºÎ£¬Õâ¸ö³ÌÐòÖ´ÐеĽá¹ûÊDz»±äµÄ¡£ËûÃÇ¿ÉÄÜÈ¥Ö´ÐÐ˯Ãß ºÍ»½ÐÑÀ´µÈ´ý¶Ô·½¡£¸¸½ø³ÌÔÚ15´ÎÑ»·ºóÍ˳ö¡£È»ºó×Ó½ø³ÌÒò¹ÜµÀÏßûÓÐд½ø³Ì¶ø¶Á µ½¡°Îļþβ¡±±êÖ¾£¬²¢Í˳ö¡£
[ ±¾Ìû×îºóÓÉ gxf ÓÚ 2007-11-24 17:24 ±à¼ ]