{"id":796,"date":"2021-06-01T19:15:56","date_gmt":"2021-06-01T11:15:56","guid":{"rendered":"https:\/\/www.sunjw.cn\/?p=796"},"modified":"2021-06-02T12:18:51","modified_gmt":"2021-06-02T04:18:51","slug":"linux-select","status":"publish","type":"post","link":"https:\/\/www.sunjw.cn\/index.php\/2021\/06\/01\/linux-select\/","title":{"rendered":"[linux]select\u5b9e\u73b0\u975e\u963b\u585e\u5f02\u6b65\u8f93\u5165"},"content":{"rendered":"
\u6700\u8fd1\u8981\u5b9e\u73b0\u4e00\u4e2a\u975e\u963b\u585e\u8f93\u5165\u7684C\u4ee3\u7801\uff0c\u67e5\u5230\u53ef\u4ee5\u901a\u8fc7select\u51fd\u6570\u6765\u5b8c\u6210\u3002<\/div>\n
select\u7528\u4e8e\u540c\u65f6\u76d1\u63a7\u591a\u4e2afd\uff0c\u5728io\u53ef\u8bfb\/\u5199\u65f6\u8fd4\u56de\u3002<\/div>\n
\u6b63\u5e38\u6765\u8bf4\uff0cselect\u662f\u963b\u585e\u7684\uff0c\u9664\u975e\u8d85\u65f6\u6216\u8005\u7b49\u5f85\u7684fd\u5185\u5bb9\u53d1\u751f\u53d8\u5316\u3002\u56e0\u6b64\uff0c\u6211\u6211\u4eec\u5c06select\u7684\u8d85\u65f6\u65f6\u95f4\u8bbe\u4e3a0\uff0c\u4fbf\u53ef\u4ee5\u975e\u963b\u585e\u3002\u6309\u7167\u8fd4\u56de\u6765\u5224\u65ad\u5f53\u524d\u76d1\u89c6\u7684fd\u5185\u5bb9\u662f\u5426\u53d8\u5316\uff0c\u4ece\u800c\u6839\u636e\u8fd9\u4e2a\u8fd4\u56de\u8fdb\u884c\u76f8\u5e94\u7684\u64cd\u4f5c\u3002<\/div>\n
\u4ee5\u4e0b\u4e3a\u6839\u636eselect man page\u4fee\u6539\u7684\u975e\u963b\u585e\u8f93\u5165\u7684\u4ee3\u7801\u3002<\/div>\n
int main(void)<\/div>\n
{<\/div>\n
fd_set rfds;\/\/fd\u96c6\u5408<\/div>\n
struct timeval tv;<\/div>\n
int retval;<\/div>\n
\/* Watch stdin (fd 0) to see when it has input. *\/<\/div>\n
\/* Wait up to five seconds. *\/<\/div>\n
char c;<\/div>\n
char buf[100];<\/div>\n
while(1)<\/div>\n
{<\/div>\n
\/\/select\u8fd4\u56de\u540e\u4f1a\u628a\u4ee5\u524d\u52a0\u5165\u7684\u4f46\u5e76\u65e0\u4e8b\u4ef6\u53d1\u751f\u7684fd\u6e05\u7a7a\uff0c\u5219\u6bcf\u6b21\u5f00\u59cbselect\u524d\u90fd\u8981\u91cd\u65b0\u4ecearray\u53d6\u5f97fd\u9010\u4e00\u52a0\u5165<\/div>\n
FD_ZERO(&rfds);<\/div>\n
FD_SET(0, &rfds); \/\/\u76d1\u63a7fd\u4e3a0\uff0c\u4e5f\u5c31\u662fstdin<\/div>\n
\/\/FD_ISSET(int fd, fd_set *set);\/\/\u82e5\u5b58\u5728\u591a\u4e2afd\uff0c\u53ef\u4ee5\u7528\u6b64\u63a5\u53e3\u9010\u4e2a\u5224\u65ad<\/div>\n
tv.tv_sec = 0; \/\/\u65f6\u95f4\u8bbe0\uff0c\u65e0\u8bbafd\u6709\u6ca1\u6709\u6570\u636e\u5747\u7ee7\u7eed\u8fd0\u884c<\/div>\n
tv.tv_usec = 0;<\/div>\n
retval = select(1<\/span>, &rfds, NULL, NULL, &tv); \/\/1 here means (fd=0)+1,see man page<\/div>\n
\/* Don’t rely on the value of tv now! *\/<\/div>\n
if (retval == -1)<\/div>\n
perror(“select()”);<\/div>\n
else if (retval)\/\/select\u68c0\u6d4b\u5230\u6709\u6570\u636e\u4e4b\u540e\uff0c\u901a\u8fc7read\u8bfbfd=0\u7684\u6570\u636e<\/div>\n
{<\/div>\n
int ret = 0;<\/div>\n
ret = read(0, buf, 100);<\/div>\n
if(ret > 0)<\/div>\n
{<\/div>\n
int i = 0;<\/div>\n
for(i = 0;i < ret; i++)<\/div>\n
printf(“%c”, buf[i]);<\/div>\n
}<\/div>\n
\/\/printf(“Data is available now.\\n”);<\/div>\n
}<\/div>\n
\/* FD_ISSET(0, &rfds) will be true. *\/<\/div>\n
else\/\/\u6b64\u5904\u4e3a\u975e\u963b\u585e\u6b63\u5e38\u8fd0\u884c\u7684\u7a0b\u5e8f<\/div>\n
{<\/div>\n
<\/div>\n
\/\/printf(“No data\\n”);<\/div>\n
}<\/div>\n
retval = 0;<\/div>\n
}<\/div>\n
exit(EXIT_SUCCESS);<\/div>\n
}<\/div>\n","protected":false},"excerpt":{"rendered":"

\u6700\u8fd1\u8981\u5b9e\u73b0\u4e00\u4e2a\u975e\u963b\u585e\u8f93\u5165\u7684C\u4ee3\u7801\uff0c\u67e5\u5230\u53ef\u4ee5\u901a\u8fc7select\u51fd\u6570\u6765\u5b8c\u6210\u3002 select\u7528\u4e8e\u540c\u65f6\u76d1\u63a7\u591a\u4e2afd\uff0c\u5728i […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[16,17],"tags":[],"_links":{"self":[{"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/posts\/796"}],"collection":[{"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/comments?post=796"}],"version-history":[{"count":2,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/posts\/796\/revisions"}],"predecessor-version":[{"id":798,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/posts\/796\/revisions\/798"}],"wp:attachment":[{"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/media?parent=796"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/categories?post=796"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/tags?post=796"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}