{"id":615,"date":"2014-07-17T04:30:51","date_gmt":"2014-07-17T04:30:51","guid":{"rendered":"http:\/\/ixyzero.com\/blog\/?p=615"},"modified":"2014-07-17T04:30:51","modified_gmt":"2014-07-17T04:30:51","slug":"linux-shell%e5%9f%ba%e6%9c%ac%e8%bf%90%e7%ae%97","status":"publish","type":"post","link":"https:\/\/ixyzero.com\/blog\/archives\/615.html","title":{"rendered":"Linux shell\u57fa\u672c\u8fd0\u7b97"},"content":{"rendered":"<p>shell\u811a\u672c\u4e2d\u7684\u64cd\u4f5c\u9ed8\u8ba4\u662f\u5b57\u7b26\u4e32\u64cd\u4f5c\uff0c\u5728\u8981\u8fd0\u884c\u6570\u5b66\u8fd0\u7b97\u7b26\u7684\u65f6\u5019\u53ef\u80fd\u5f97\u5230\u610f\u60f3\u4e0d\u5230\u7684\u7b54\u6848\uff1a<\/p>\n<p># var=1<br \/>\n# var=$var+1<br \/>\n# echo $var<br \/>\n1+1<\/p>\n<p>\u4ece\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\u53ef\u4ee5\u770b\u51fa\u5728shell\u4e2d\u4f7f\u7528&#8217;+&#8217;\u9ed8\u8ba4\u8fdb\u884c\u7684\u662f\u5b57\u7b26\u4e32\u8fde\u63a5\u7684\u64cd\u4f5c\uff0c\u9700\u8981\u6ce8\u610f\u7684\u662f\u7a7a\u683c\u3002<\/p>\n<p><strong><span style=\"color: #ff0000;\">\u5728shell\u4e2d\u53ef\u4ee5\u4f7f\u7528let\u6765\u6307\u793a\u7b97\u672f\u8868\u8fbe\u5f0f\uff0clet\u8868\u8fbe\u5f0f\u5185\u53d8\u91cf\u4e0d\u7528\u52a0$\u7b26\u53f7<\/span><\/strong>\uff1a<\/p>\n<p># var=1<br \/>\n# let &#8220;var+=1&#8221; #\u6216 let var+=1 \uff0c\u4f46\u8fd9\u79cd\u5199\u6cd5\u5728\u8fd0\u7b97\u7b26\u95f4\u4e0d\u80fd\u6709\u7a7a\u683c<br \/>\n# echo $var<br \/>\n2<\/p>\n<p>\u8fd9\u5176\u4e2d\u7684<strong><span style=\"color: #ff0000;\">let\u53ef\u4ee5\u7528(())\u4ee3\u66ff<\/span><\/strong>\uff0clet &#8220;j=i*6+2&#8243;\u7b49\u4ef7\u4e8e((j=i*6+2))\uff0c\u5c31\u50cf\u5f88\u591a\u7684\u5faa\u73af\u4e2d\u7528\u6cd5\u4e00\u6837\u3002<\/p>\n<p>\u6ce8\u610f\uff1a <span style=\"color: #ff0000;\">let\u5fc5\u987b\u662f\u5b8c\u6574\u7684\u7b97\u672f\u8868\u8fbe\u5f0f\uff0c\u5373\u6709\u7b49\u53f7\u4e24\u8fb9<\/span><br \/>\n(())\u3001expr \u53ef\u4ee5\u53ea\u6709\u7b49\u53f7\u53f3\u8fb9\u7684\u8ba1\u7b97\uff0c\u7531$((&#8230;))\u3001$(expr &#8230;)\u3001`expr &#8230;` \u67e5\u770b\u8fd4\u56de\u7ed3\u679c<\/p>\n<p># var=1<br \/>\n# ((var++)) #\u76f4\u63a5\u67e5\u770b\u7ed3\u679c\uff1aecho $((var++))<br \/>\n# echo $var<br \/>\n2<\/p>\n<p>\u8fd8\u6709\u4e00\u79cd\u5199\u6cd5\uff1a<br \/>\n# var=1<br \/>\n# var=$[$var+1]<br \/>\n# echo $var<br \/>\n2<\/p>\n<p>\u4f7f\u7528expr\uff0c\u9700\u8981\u6ce8\u610f\u7684\u662f\u5176\u4e2d\u7684\u90a3\u4e2a\u7b26\u53f7\u5e76\u4e0d\u662f\u5355\u5f15\u53f7\uff0c\u800c\u662f\u201c1\u201d\u5de6\u8fb9\u7684\u90a3\u4e2a\u952e(\u53cd\u5f15\u53f7)<\/p>\n<p>\u6ce8\u610f\uff1a<span style=\"color: #ff0000;\">\u5c06\u9700\u8981\u8fd0\u7b97\u7684\u8868\u8fbe\u5f0f\u5199\u5165\u5728 expr \u540e\u9762\uff0c\u5e76<strong>\u4fdd\u8bc1\u53c2\u6570\u4e0e\u8fd0\u7b97\u7b26\u53f7\u4e2d\u95f4\u6709\u7a7a\u683c\u9694\u5f00<\/strong><\/span>\u3002<\/p>\n<p># var=1<br \/>\n# var=`expr $var + 1`<br \/>\n# echo $var<br \/>\n2<\/p>\n<p>1.<span style=\"color: #ff0000;\">\u5728 shell \u4e2d$() \u4e0e &#8220;\u7b49\u6548\u3002\u6267\u884c\u4e2d\u95f4\u5305\u542b\u7684\u547d\u4ee4\u8bed\u53e5\uff0c\u8fd4\u56de\u6267\u884c\u7ed3\u679c<\/span>\u3002<br \/>\n2.\u4ece\u6548\u7387\u6765\u8bf4 let==(()) &gt; expr &gt; bc\u3002let\u548c(())\u8fd0\u884c\u662f\u5185\u5efa\u547d\u4ee4\uff0c\u4f7f\u7528\u76f8\u540c\u7684\u7b97\u6cd5\u3002<br \/>\n3.<span style=\"color: #ff0000;\">let \u548c expr \u7684\u8fd0\u7b97\u662f\u6574\u6570\u8fd0\u7b97\uff0c\u4e0d\u5305\u62ec\u6d6e\u70b9\u9884\u7b97<\/span>\u3002<br \/>\n4.expr \u548c bc \u662f\u5916\u90e8\u7a0b\u5e8f\uff0cexpr\u7684\u4f53\u79ef\u51e0\u4e4e\u7b49\u4e8ebc\u76841\/3\uff0c\u6267\u884c\u4e00\u6b21\u88c5\u5165\u5185\u5b58\u6240\u6d88\u8017\u7684\u65f6\u95f4\u5c31\u4e0d\u4e00\u6837\u3002<br \/>\n5.\u4ece\u8fd0\u7b97\u80fd\u529b\u6765\u8bf4\uff0cbc\u6392\u7b2c\u4e00\u4f4d\u3002<\/p>\n<p>\u4e0a\u9762\u7684\u8fd9\u51e0\u79cd\u505a\u6cd5\u90fd\u662f\u53ea\u80fd\u5904\u7406\u6574\u6570\u8fd0\u7b97\uff0c\u4e0b\u9762\u7684\u8fd9\u79cd\u505a\u6cd5\u662f\u53ef\u4ee5\u5904\u7406\u6d6e\u70b9\u6570\u7684\uff1a<br \/>\n# var=1<br \/>\n# var=`echo &#8220;scale=1;$var*2.0&#8243;|bc` bc\u9884\u8bbe\u8f93\u51fa\u6574\u6570\uff0c\u7528scale \u6307\u5b9a\u5c0f\u6570\u70b9\u4e0b\u4f4d\u6570<br \/>\n# echo $var<br \/>\n2.0<\/p>\n<p>\u6ce8\u610f\u662f\u53cd\u5f15\u53f7\u800c\u4e0d\u662f\u5355\u5f15\u53f7\uff0cbc\u662flinux\u4e0a\u9762\u7684\u4e00\u4e2a\u8ba1\u7b97\u5668\uff0c\u652f\u6301\u9664\u4f4d\u8fd0\u7b97\u4ee5\u5916\u7684\u6240\u6709\u8fd0\u7b97\u529f\u80fd\u3002<\/p>\n<p>\u53e6\u5916\u4e00\u4e2a\u652f\u6301\u6d6e\u70b9\u8fd0\u7b97\u7684\u65b9\u6cd5\u662fawk\uff1a<br \/>\n# var=1<br \/>\n# var=`echo &#8220;$var 1.1&#8243;|awk &#8216;{printf(&#8220;%g&#8221;,$1+$2)}&#8217;`<br \/>\n# echo $var<br \/>\n2.1<\/p>\n<p>$ c=$(awk &#8216;<span style=\"color: #ff0000;\"><strong>BEGIN<\/strong><\/span>{print 7.01*5-4.01 }&#8217;)<br \/>\n$ echo $c<\/p>\n<hr \/>\n<h4>Bash shell \u7684\u7b97\u672f\u8fd0\u7b97\u6709\u56db\u79cd\u65b9\u5f0f\uff1a<\/h4>\n<h5>1\uff1a\u4f7f\u7528 expr<\/h5>\n<p>\u52a0\u6cd5 r=`expr 4 + 5`<br \/>\necho $r<br \/>\n\u6ce8\u610f\uff01\u5728 &#8216;4&#8217; &#8216;+&#8217; &#8216;5&#8217; \u8fd9\u4e09\u8005\u4e4b\u95f4\u8981\u6709\u7a7a\u767d<br \/>\nr=`expr 4 * 5` #\u9519\u8bef<br \/>\n\u4e58\u6cd5 r=`expr 4 * 5`<\/p>\n<h5>2\uff1a\u4f7f\u7528 $(( ))<\/h5>\n<p>r=$(( 4 + 5 ))<br \/>\necho $r<\/p>\n<h5>3\uff1a\u4f7f\u7528 $[ ]<\/h5>\n<p>r=$[ 4 + 5 ]<br \/>\necho $r<\/p>\n<p>\u4e58\u6cd5<br \/>\nr=`expr 4 * 5`<br \/>\necho $r<br \/>\nr=$(( 4 * 5 ))<br \/>\necho $r<br \/>\nr=$[ 4 * 5 ]<br \/>\necho $r<\/p>\n<p>\u9664\u6cd5<br \/>\nr=`expr 40 \/ 5`<br \/>\nr=$(( 40 \/ 5 ))<br \/>\nr=$[ 40 \/ 5 ]<br \/>\necho $r<\/p>\n<p>\u51cf\u6cd5<br \/>\nr=`expr 40 &#8211; 5`<br \/>\nr=$(( 40 &#8211; 5 ))<br \/>\nr=$[ 40 &#8211; 5 ]<br \/>\necho $r<\/p>\n<p>\u6c42\u4f59\u6570<br \/>\nr=$[ 100 % 43 ]<br \/>\necho $r<\/p>\n<p>\u4e58\u5e42 (\u5982 2 \u7684 3 \u6b21\u65b9)<br \/>\nr=$(( 2 ** 3 ))<br \/>\nr=$[ 2 ** 3 ]<br \/>\necho $r<br \/>\n\u6ce8\uff1aexpr \u6c92\u6709\u4e58\u5e42<\/p>\n<h5>4\uff1a\u4f7f\u7528let \u547d\u4ee4<\/h5>\n<p>\u52a0\u6cd5\uff1a<br \/>\nn=10<br \/>\nlet n=n+1<br \/>\necho $n #n=11<\/p>\n<p>\u4e58\u6cd5\uff1a<br \/>\nlet m=n*10<br \/>\necho $m<\/p>\n<p>\u9664\u6cd5\uff1a<br \/>\nlet r=m\/10<br \/>\necho $r<\/p>\n<p>\u6c42\u4f59\u6570\uff1a<br \/>\nlet r=m%7<br \/>\necho $r<\/p>\n<p>\u4e58\u51aa\uff1a<br \/>\nlet r=m**2<br \/>\necho $r<\/p>\n<p><span style=\"color: #ff0000;\">\u867d\u7136 Bash shell \u6709\u56db\u79cd\u7b97\u672f\u8fd0\u7b97\u65b9\u6cd5\uff0c\u4f46\u5e76\u4e0d\u662f\u6bcf\u4e00\u79cd\u90fd\u662f\u8de8\u5e73\u53f0\u7684\uff0c\u5efa\u8bae\u4f7f\u7528expr<\/span>\u3002<br \/>\n\u53e6\u5916\uff0c\u6211\u4eec\u5728 script \u4e2d\u7ecf\u5e38\u6709\u52a01\u64cd\u4f5c\uff0c\u4ee5\u4e0b\u56db\u6cd5\u7686\u53ef\uff1a<br \/>\nm=$[ m + 1]<br \/>\nm=`expr $m + 1`<br \/>\nm=$(($m + 1))<br \/>\nlet m=m+1<\/p>\n<h6>\u53c2\u8003\u5730\u5740\uff1a<\/h6>\n<ul>\n<li><a href=\"http:\/\/www.cppblog.com\/fwxjj\/archive\/2009\/09\/04\/95342.html\" target=\"_blank\">LinuxShell\u7b97\u672f\u8fd0\u7b97<\/a><\/li>\n<li><a href=\"http:\/\/www.cnblogs.com\/yfanqiu\/archive\/2012\/05\/10\/2494031.html\" target=\"_blank\">Linux shell\u57fa\u672c\u8fd0\u7b97<\/a><\/li>\n<\/ul>\n<hr \/>\n<p>\u4e0b\u9762\u662f\u4e00\u4e2a\u7528awk\u547d\u4ee4\u8ba1\u7b97\u4e00\u4e2a\u975e\u5e38\u5927\u7684\u6570\u636e\u6587\u4ef6\u7684\u4f8b\u5b50\uff1a<\/p>\n<p>cat rands20M.txt | awk &#8216;{s+=$1} END {print s}&#8217;<\/p>\n<p><a href=\"http:\/\/ixyzero.com\/blog\/archives\/98.html\" target=\"_blank\">Awk\u7684\u4e00\u4e9b\u6280\u5de7\u603b\u7ed3[\u4e0d\u5b9a\u671f\u66f4\u65b0]<\/a><\/p>\n<p>\u82e5\u4f60\u9700\u8981\u76f4\u63a5\u7528\u7ec8\u7aef\uff0c\u800c\u4e0d\u662f\u4f9d\u9760\u4efb\u4f55shell\u811a\u672c\u6765\u8fdb\u884c\u5b9e\u6570\u8ba1\u7b97\u3002\u4f60\u4f1a\u600e\u4e48\u505a\uff08\u6bd4\u5982\u5b9e\u65707.56+2.453\uff09\uff1f<br \/>\n\u7b54\u6848 : \u6211\u4eec\u9700\u8981\u7528\u5982\u4e0b\u6240\u8ff0\u7684\u7279\u6b8a\u65b9\u5f0f\u4f7f\u7528bc\u547d\u4ee4\uff08$ echo 7.56 + 2.453 | bc\uff09\u5c067.56+2.453\u4f5c\u4e3a\u8f93\u5165\u901a\u8fc7\u7ba1\u9053\u8fdb\u5165bc\u4e2d\u3002<\/p>\n<pre class=\"lang:default decode:true \"># curl -s http:\/\/nis.fzu.edu.cn\/practice\/zhuabao\/1_2.php | grep -o \"(.* \"\n(1784 + 529) x (8784 - 80) - (687 + 212 - 295) x 499\n\n# result=`curl -s http:\/\/nis.fzu.edu.cn\/practice\/zhuabao\/1_2.php | grep -o \"(.* \" | sed \"s\/x\/*\/g\" | bc`<\/pre>\n<p>&nbsp;<\/p>\n<p><span style=\"color: #ff0000;\"><strong>\u6ce8\u610f\u7a7a\u683c\uff01\uff01\uff01<\/strong><\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>shell\u811a\u672c\u4e2d\u7684\u64cd\u4f5c\u9ed8\u8ba4\u662f\u5b57\u7b26\u4e32\u64cd\u4f5c\uff0c\u5728\u8981\u8fd0\u884c\u6570\u5b66\u8fd0\u7b97\u7b26\u7684\u65f6\u5019\u53ef\u80fd\u5f97\u5230\u610f\u60f3\u4e0d\u5230\u7684\u7b54\u6848\uff1a # var=1 #  [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23,11],"tags":[65],"class_list":["post-615","post","type-post","status-publish","format-standard","hentry","category-knowledgebase-2","category-linux","tag-shell"],"views":2518,"_links":{"self":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/615","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/comments?post=615"}],"version-history":[{"count":0,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/615\/revisions"}],"wp:attachment":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/media?parent=615"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/categories?post=615"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/tags?post=615"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}