{"id":255290,"date":"2015-08-11T22:20:42","date_gmt":"2015-08-11T14:20:42","guid":{"rendered":"http:\/\/blog.zhenglei.net\/?p=255290"},"modified":"2015-08-11T22:20:42","modified_gmt":"2015-08-11T14:20:42","slug":"linux-%e6%8a%80%e5%b7%a7-bash-%e6%b5%8b%e8%af%95%e5%92%8c%e6%af%94%e8%be%83%e5%87%bd%e6%95%b0","status":"publish","type":"post","link":"https:\/\/blog.zhenglei.net\/?p=255290","title":{"rendered":"Linux \u6280\u5de7: Bash \u6d4b\u8bd5\u548c\u6bd4\u8f83\u51fd\u6570"},"content":{"rendered":"<div id=\"ibm-leadspace-head\">\n<div id=\"ibm-leadspace-body\">\n<ul id=\"ibm-navigation-trail\">\n<li><a href=\"http:\/\/www.ibm.com\/developerworks\/cn\/\">developerWorks \u4e2d\u56fd<\/a><\/li>\n<li><a href=\"http:\/\/www.ibm.com\/developerworks\/cn\/topics\/\">\u6280\u672f\u4e3b\u9898<\/a><\/li>\n<li><a href=\"http:\/\/www.ibm.com\/developerworks\/cn\/linux\/\">Linux<\/a><\/li>\n<li><a href=\"http:\/\/www.ibm.com\/developerworks\/cn\/views\/linux\/libraryview.jsp\">\u6587\u6863\u5e93<\/a><\/li>\n<\/ul>\n<h1>Linux \u6280\u5de7: Bash \u6d4b\u8bd5\u548c\u6bd4\u8f83\u51fd\u6570<\/h1>\n<p><em>test\u3001[\u3001[[\u3001((\u3001\u548c if-then-else \u89e3\u5bc6<\/em><\/p>\n<\/div>\n<div id=\"dw-summary-area\" class=\"dw-summary-columns\">\n<div class=\"ibm-col-6-4\">\n<p>\u60a8\u662f\u5426\u4e3a Bash shell \u4e2d\u5927\u91cf\u7684\u6d4b\u8bd5\u548c\u6bd4\u8f83\u9009\u9879\u800c\u56f0\u60d1\u5462\uff1f\u8fd9\u4e2a\u6280\u5de7\u53ef\u4ee5\u5e2e\u52a9\u60a8\u89e3\u5bc6\u4e0d\u540c\u7c7b\u578b\u7684\u6587\u4ef6\u3001\u7b97\u672f\u548c\u5b57\u7b26\u4e32\u6d4b\u8bd5\uff0c\u8fd9\u6837\u60a8\u5c31\u80fd\u591f\u77e5\u9053\u4ec0\u4e48\u65f6\u5019\u4f7f\u7528 <code>test<\/code>\u3001 <code>[\u00a0]<\/code>\u3001 <code>[[\u00a0]]<\/code>\u3001 <code>((\u00a0))<\/code> \u6216 <code>if-then-else<\/code> \u4e86\u3002<\/p>\n<p class=\"ibm-no-print ibm-ind-link\"><a class=\"ibm-forward-link\" href=\"http:\/\/www.ibm.com\/developerworks\/cn\/views\/linux\/articles.jsp?view_by=search&amp;search_by=Linux+%E6%8A%80%E5%B7%A7\">\u67e5\u770b\u672c\u7cfb\u5217\u66f4\u591a\u5185\u5bb9<\/a> <span class=\"dw-summary-bar\">|<\/span> <span id=\"nCmts\">0<img loading=\"lazy\" decoding=\"async\" class=\"dw-cmts-arrow\" src=\"http:\/\/dw1.s81c.com\/developerworks\/i\/v17\/dw-cmts-arrow.png\" alt=\"\" width=\"7\" height=\"7\" \/> <a class=\"dw-cmt-link\" href=\"http:\/\/www.ibm.com\/developerworks\/cn\/linux\/l-bash-test.html#icomments\">\u8bc4\u8bba\uff1a<\/a><\/span><\/p>\n<\/div>\n<div class=\"ibm-col-6-2 dw-toc-margin\">\n<p class=\"dw-summary-author\"><a class=\"ibm-popup-link\" href=\"http:\/\/www.ibm.com\/developerworks\/cn\/linux\/l-bash-test.html#authorN10024\">Ian Shields<\/a>, \u9ad8\u7ea7\u7a0b\u5e8f\u5458, IBM<\/p>\n<p class=\"dw-summary-date\">2007 \u5e74 3 \u6708 16 \u65e5<\/p>\n<div id=\"dw-toc\" class=\"ibm-container\">\n<div class=\"ibm-container-body\">\n<ul class=\"ibm-twisty\">\n<li><a class=\"ibm-twisty-trigger ibm-twisty-trigger-closed\" href=\"http:\/\/www.ibm.com\/developerworks\/cn\/linux\/l-bash-test.html#toggle\"><img decoding=\"async\" src=\"http:\/\/www.ibm.com\/i\/c.gif\" alt=\"+\" \/><\/a><span class=\"ibm-twisty-head\">\u5185\u5bb9<\/span><\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"ibm-pcon\">\n<div id=\"ibm-content\">\n<div id=\"ibm-content-body\">\n<div id=\"ibm-content-main\">\n<div class=\"ibm-columns\">\n<div class=\"ibm-col-1-1\">\n<div id=\"dwc-exp-a\" class=\"dw-article-sidebar dw-bluemix\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/dw1.s81c.com\/developerworks\/i\/bluemix-graphic.png\" alt=\"\" width=\"64\" height=\"64\" \/>\u5728 IBM Bluemix \u4e91\u5e73\u53f0\u4e0a\u5f00\u53d1\u5e76\u90e8\u7f72\u60a8\u7684\u4e0b\u4e00\u4e2a\u5e94\u7528\u3002<\/p>\n<p class=\"ibm-button-link-alternate dw-button-green\"><a id=\"tutc-sbar-bmix-home-btn-ABa\" class=\"dw-button-large\" href=\"https:\/\/developer.ibm.com\/sso\/bmregistration?lang=zh_CN&amp;ca=dwchina-_-bluemix-_-linux-_-sidebar\">\u5f00\u59cb\u60a8\u7684\u8bd5\u7528<\/a><\/p>\n<\/div>\n<p>Bash shell \u5728\u5f53\u4eca\u7684\u8bb8\u591a Linux\u00ae \u548c UNIX\u00ae \u7cfb\u7edf\u4e0a\u90fd\u53ef\u4f7f\u7528\uff0c\u662f Linux \u4e0a\u5e38\u89c1\u7684\u9ed8\u8ba4 shell\u3002Bash \u5305\u542b\u5f3a\u5927\u7684\u7f16\u7a0b\u529f\u80fd\uff0c\u5176\u4e2d\u5305\u62ec\u4e30\u5bcc\u7684\u53ef\u6d4b\u8bd5\u6587\u4ef6\u7c7b\u578b\u548c\u5c5e\u6027\u7684\u51fd\u6570\uff0c\u4ee5\u53ca\u5728\u591a\u6570\u7f16\u7a0b\u8bed\u8a00\u4e2d\u53ef\u4ee5\u4f7f\u7528\u7684\u7b97\u672f\u548c\u5b57\u7b26\u4e32\u6bd4\u8f83\u51fd\u6570\u3002\u7406\u89e3\u4e0d\u540c\u7684\u6d4b\u8bd5\u5e76\u8ba4\u8bc6\u5230 shell \u8fd8\u80fd\u628a\u4e00\u4e9b\u64cd\u4f5c\u7b26\u89e3\u91ca\u6210 shell \u5143\u5b57\u7b26\uff0c\u662f\u6210\u4e3a\u9ad8\u7ea7 shell \u7528\u6237\u7684\u91cd\u8981\u4e00\u6b65\u3002\u8fd9\u7bc7\u6587\u7ae0\u6458\u81ea developerWorks \u6559\u7a0b <a href=\"http:\/\/www.ibm.com\/developerworks\/cn\/edu\/l-dw-linux-lpic1109-i.html\">LPI 102 \u8003\u8bd5\u51c6\u5907\uff0c\u4e3b\u9898 109: Shell\u3001\u811a\u672c\u3001\u7f16\u7a0b\u548c\u7f16\u8bd1<\/a>\uff0c\u4ecb\u7ecd\u4e86\u5982\u4f55\u7406\u89e3\u548c\u4f7f\u7528 Bash shell \u7684\u6d4b\u8bd5\u548c\u6bd4\u8f83\u64cd\u4f5c\u3002<\/p>\n<p>\u8fd9 \u4e2a\u6280\u5de7\u89e3\u91ca\u4e86 shell \u6d4b\u8bd5\u548c\u6bd4\u8f83\u51fd\u6570\uff0c\u6f14\u793a\u4e86\u5982\u4f55\u5411 shell \u6dfb\u52a0\u7f16\u7a0b\u529f\u80fd\u3002\u60a8\u53ef\u80fd\u5df2\u7ecf\u770b\u5230\u8fc7\u4f7f\u7528 &amp;&amp; \u548c || \u64cd\u4f5c\u7b26\u7684\u7b80\u5355 shell \u903b\u8f91\uff0c\u5b83\u5141\u8bb8\u60a8\u6839\u636e\u524d\u4e00\u6761\u547d\u4ee4\u7684\u9000\u51fa\u72b6\u6001\uff08\u6b63\u786e\u9000\u51fa\u6216\u4f34\u968f\u9519\u8bef\u9000\u51fa\uff09\u800c\u6267\u884c\u540e\u4e00\u6761\u547d\u4ee4\u3002\u5728\u8fd9\u4e2a\u6280\u5de7\u4e2d\uff0c\u5c06\u770b\u5230\u5982\u4f55\u628a\u8fd9\u4e9b\u57fa\u672c\u7684\u6280\u672f\u6269\u5c55\u6210\u66f4\u590d\u6742\u7684 shell \u7f16\u7a0b\u3002<\/p>\n<h2 id=\"N10061\">\u6d4b\u8bd5<\/h2>\n<p>\u5728\u4efb\u4f55\u4e00\u79cd\u7f16\u7a0b\u8bed\u8a00\u4e2d\uff0c\u5b66\u4e60\u4e86\u5982\u4f55\u7ed9\u53d8\u91cf\u5206\u914d\u503c\u548c\u4f20\u9012\u53c2\u6570\u4e4b\u540e\uff0c\u90fd\u9700\u8981\u6d4b\u8bd5\u8fd9\u4e9b\u503c\u548c\u53c2\u6570\u3002\u5728 shell \u4e2d\uff0c\u6d4b\u8bd5\u4f1a\u8bbe\u7f6e\u8fd4\u56de\u7684\u72b6\u6001\uff0c\u8fd9\u4e0e\u5176\u4ed6\u547d\u4ee4\u6267\u884c\u7684\u529f\u80fd\u76f8\u540c\u3002\u5b9e\u9645\u4e0a\uff0c<code>test<\/code> \u662f\u4e2a\u5185\u7f6e<em>\u547d\u4ee4<\/em>\uff01<\/p>\n<h3 id=\"N1006D\">test \u548c [<\/h3>\n<p>\u5185\u7f6e\u547d\u4ee4 <code>test<\/code> \u6839\u636e\u8868\u8fbe\u5f0f<em>expr<\/em> \u6c42\u503c\u7684\u7ed3\u679c\u8fd4\u56de 0\uff08\u771f\uff09\u6216 1\uff08\u5047\uff09\u3002\u4e5f\u53ef\u4ee5\u4f7f\u7528\u65b9\u62ec\u53f7\uff1a<code>test\u00a0<em>expr<\/em><\/code> \u548c [ <em>expr<\/em> ] \u662f\u7b49\u4ef7\u7684\u3002 \u53ef\u4ee5\u7528 <code>$?<\/code> \u68c0\u67e5\u8fd4\u56de\u503c\uff1b\u53ef\u4ee5\u4f7f\u7528 &amp;&amp; \u548c || \u64cd\u4f5c\u8fd4\u56de\u503c\uff1b\u4e5f\u53ef\u4ee5\u7528\u672c\u6280\u5de7\u540e\u9762\u4ecb\u7ecd\u7684\u5404\u79cd\u6761\u4ef6\u7ed3\u6784\u6d4b\u8bd5\u8fd4\u56de\u503c\u3002<\/p>\n<h5 id=\"N10087\">\u6e05\u5355 1. \u4e00\u4e9b\u7b80\u5355\u6d4b\u8bd5<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$ test 3 -gt 4 &amp;&amp; echo True || echo false\r\nfalse\r\n[ian@pinguino ~]$ [ \"abc\" != \"def\" ];echo $?\r\n0\r\n[ian@pinguino ~]$ test -d \"$HOME\" ;echo $?\r\n0<\/pre>\n<\/div>\n<p>\u5728\u6e05\u5355 1 \u7684\u7b2c\u4e00\u4e2a\u793a\u4f8b\u4e2d\uff0c<code>-gt<\/code> \u64cd\u4f5c\u7b26\u5bf9\u4e24\u4e2a\u5b57\u7b26\u503c\u4e4b\u95f4\u6267\u884c\u7b97\u672f\u6bd4\u8f83\u3002\u5728\u7b2c\u4e8c\u4e2a\u793a\u4f8b\u4e2d\uff0c\u7528 <code>[\u00a0]<\/code> \u7684\u5f62\u5f0f\u6bd4\u8f83\u4e24\u4e2a\u5b57\u7b26\u4e32\u4e0d\u76f8\u7b49\u3002\u5728\u6700\u540e\u4e00\u4e2a\u793a\u4f8b\u4e2d\uff0c\u6d4b\u8bd5 HOME \u53d8\u91cf\u7684\u503c\uff0c\u7528\u5355\u76ee\u64cd\u4f5c\u7b26 <code>-d<\/code> \u68c0\u67e5\u5b83\u662f\u4e0d\u662f\u76ee\u5f55\u3002<\/p>\n<p>\u53ef\u4ee5\u7528 <code>-eq<\/code>\u3001 &#8211;<code>ne<\/code>\u3001<code>-lt<\/code>\u3001 &#8211;<code>le<\/code>\u3001 &#8211;<code>gt<\/code> \u6216 &#8211;<code>ge<\/code> \u6bd4\u8f83\u7b97\u672f\u503c\uff0c\u5b83\u4eec\u5206\u522b\u8868\u793a\u7b49\u4e8e\u3001\u4e0d\u7b49\u4e8e\u3001\u5c0f\u4e8e\u3001\u5c0f\u4e8e\u7b49\u4e8e\u3001\u5927\u4e8e\u3001\u5927\u4e8e\u7b49\u4e8e\u3002<\/p>\n<p>\u53ef\u4ee5\u5206\u522b\u7528\u64cd\u4f5c\u7b26 <code>=<\/code>\u3001 <code>!=<\/code>\u3001<code>&lt;<\/code> \u548c <code>&gt;<\/code> \u6bd4\u8f83\u5b57\u7b26\u4e32\u662f\u5426\u76f8\u7b49\u3001\u4e0d\u76f8\u7b49\u6216\u8005\u7b2c\u4e00\u4e2a\u5b57\u7b26\u4e32\u7684\u6392\u5e8f\u5728\u7b2c\u4e8c\u4e2a\u5b57\u7b26\u4e32\u7684\u524d\u9762\u6216\u540e\u9762\u3002\u5355\u76ee\u64cd\u4f5c\u7b26 <code>-z<\/code> \u6d4b\u8bd5 null \u5b57\u7b26\u4e32\uff0c\u5982\u679c\u5b57\u7b26\u4e32\u975e\u7a7a <code>-n<\/code> \u8fd4\u56de True\uff08\u6216\u8005\u6839\u672c\u6ca1\u6709\u64cd\u4f5c\u7b26\uff09\u3002<\/p>\n<p><strong>\u8bf4\u660e\uff1a<\/strong>shell \u4e5f\u7528 <code>&lt;<\/code> \u548c <code>&gt;<\/code> \u64cd\u4f5c\u7b26\u8fdb\u884c\u91cd\u5b9a\u5411\uff0c\u6240\u4ee5\u5fc5\u987b\u7528 <code>\\&lt;<\/code> \u6216 <code>\\&gt;<\/code> \u52a0\u4ee5\u8f6c\u4e49\u3002\u6e05\u5355 2 \u663e\u793a\u4e86\u5b57\u7b26\u4e32\u6d4b\u8bd5\u7684\u66f4\u591a\u793a\u4f8b\u3002\u68c0\u67e5\u5b83\u4eec\u662f\u5426\u5982\u60a8\u9884\u671f\u7684\u4e00\u6837\u3002<\/p>\n<h5 id=\"N100D3\">\u6e05\u5355 2. \u4e00\u4e9b\u5b57\u7b26\u4e32\u6d4b\u8bd5<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$ test \"abc\" = \"def\" ;echo $?\r\n1\r\n[ian@pinguino ~]$ [ \"abc\" != \"def\" ];echo $?\r\n0\r\n[ian@pinguino ~]$ [ \"abc\" \\&lt; \"def\" ];echo $?\r\n0\r\n[ian@pinguino ~]$ [ \"abc\" \\&gt; \"def\" ];echo $?\r\n1\r\n[ian@pinguino ~]$ [ \"abc\" \\&lt;\"abc\" ];echo $?\r\n1\r\n[ian@pinguino ~]$ [ \"abc\" \\&gt; \"abc\" ];echo $?\r\n1<\/pre>\n<\/div>\n<p>\u8868 1 \u663e\u793a\u4e86\u4e00\u4e9b\u66f4\u5e38\u89c1\u7684\u6587\u4ef6\u6d4b\u8bd5\u3002\u5982\u679c\u88ab\u6d4b\u8bd5\u7684\u6587\u4ef6\u5b58\u5728\uff0c\u800c\u4e14\u6709\u6307\u5b9a\u7684\u7279\u5f81\uff0c\u5219\u7ed3\u679c\u4e3a True\u3002<\/p>\n<table class=\"ibm-data-table\" border=\"0\" summary=\"\" width=\"50%\" cellspacing=\"0\" cellpadding=\"0\">\n<caption><em>\u8868 1. \u4e00\u4e9b\u5e38\u89c1\u7684\u6587\u4ef6\u6d4b\u8bd5<\/em><\/caption>\n<thead>\n<tr>\n<th valign=\"bottom\">\u64cd\u4f5c\u7b26<\/th>\n<th valign=\"bottom\">\u7279\u5f81<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>-d<\/td>\n<td>\u76ee\u5f55<\/td>\n<\/tr>\n<tr>\n<td>-e<\/td>\n<td>\u5b58\u5728\uff08\u4e5f\u53ef\u4ee5\u7528 -a\uff09<\/td>\n<\/tr>\n<tr>\n<td>-f<\/td>\n<td>\u666e\u901a\u6587\u4ef6<\/td>\n<\/tr>\n<tr>\n<td>-h<\/td>\n<td>\u7b26\u53f7\u8fde\u63a5\uff08\u4e5f\u53ef\u4ee5\u7528 -L\uff09<\/td>\n<\/tr>\n<tr>\n<td>-p<\/td>\n<td>\u547d\u540d\u7ba1\u9053<\/td>\n<\/tr>\n<tr>\n<td>-r<\/td>\n<td>\u53ef\u8bfb<\/td>\n<\/tr>\n<tr>\n<td>-s<\/td>\n<td>\u975e\u7a7a<\/td>\n<\/tr>\n<tr>\n<td>-S<\/td>\n<td>\u5957\u63a5\u5b57<\/td>\n<\/tr>\n<tr>\n<td>-w<\/td>\n<td>\u53ef\u5199<\/td>\n<\/tr>\n<tr>\n<td>-N<\/td>\n<td>\u4ece\u4e0a\u6b21\u8bfb\u53d6\u4e4b\u540e\u5df2\u7ecf\u505a\u8fc7\u4fee\u6539<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u9664\u4e86\u4e0a\u9762\u7684\u5355\u76ee\u6d4b\u8bd5\uff0c\u8fd8\u53ef\u4ee5\u4f7f\u7528\u8868 2 \u6240\u793a\u7684\u53cc\u76ee\u64cd\u4f5c\u7b26\u6bd4\u8f83\u4e24\u4e2a\u6587\u4ef6\uff1a<\/p>\n<table class=\"ibm-data-table\" border=\"0\" summary=\"\" width=\"50%\" cellspacing=\"0\" cellpadding=\"0\">\n<caption><em>\u8868 2. \u6d4b\u8bd5\u4e00\u5bf9\u6587\u4ef6<\/em><\/caption>\n<thead>\n<tr>\n<th valign=\"bottom\">\u64cd\u4f5c\u7b26<\/th>\n<th valign=\"bottom\">\u4e3a True \u7684\u60c5\u51b5<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>-nt<\/td>\n<td>\u6d4b\u8bd5 file1 \u662f\u5426\u6bd4 file2 \u66f4\u65b0\u3002\u4fee\u6539\u65e5\u671f\u5c06\u7528\u4e8e\u8fd9\u6b21\u548c\u4e0b\u6b21\u6bd4\u8f83\u3002<\/td>\n<\/tr>\n<tr>\n<td>-ot<\/td>\n<td>\u6d4b\u8bd5 file1 \u662f\u5426\u6bd4 file2 \u65e7\u3002<\/td>\n<\/tr>\n<tr>\n<td>-ef<\/td>\n<td>\u6d4b\u8bd5 file1 \u662f\u4e0d\u662f file2 \u7684\u786c\u94fe\u63a5\u3002<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u5176\u4ed6\u4e00\u4e9b\u6d4b\u8bd5\u53ef\u4ee5\u7528\u6765\u6d4b\u8bd5\u6587\u4ef6\u8bb8\u53ef\u4e4b\u7c7b\u7684\u5185\u5bb9\u3002\u8bf7\u53c2\u9605 bash \u624b\u518c\u83b7\u5f97\u66f4\u591a\u7ec6\u8282\u6216\u4f7f\u7528 <code>help\u00a0test<\/code> \u67e5\u770b\u5185\u7f6e\u6d4b\u8bd5\u7684\u7b80\u8981\u4fe1\u606f\u3002\u4e5f\u53ef\u4ee5\u7528 <code>help<\/code> \u547d\u4ee4\u4e86\u89e3\u5176\u4ed6\u5185\u7f6e\u547d\u4ee4\u3002<\/p>\n<p><code>-o<\/code> \u64cd\u4f5c\u7b26\u5141\u8bb8\u6d4b\u8bd5\u5229\u7528 <code>set\u00a0-o\u00a0<em>\u9009\u9879<\/em><\/code> \u8bbe\u7f6e\u7684\u5404\u79cd shell \u9009\u9879\uff0c\u5982\u679c\u8bbe\u7f6e\u4e86\u8be5\u9009\u9879\uff0c\u5219\u8fd4\u56de True (0)\uff0c\u5426\u5219\u8fd4\u56de False (1)\uff0c\u5982\u6e05\u5355 3 \u6240\u793a\u3002<\/p>\n<h5 id=\"N1015D\">\u6e05\u5355 3. \u6d4b\u8bd5 shell \u9009\u9879<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$ set +o nounset\r\n[ian@pinguino ~]$ [ -o nounset ];echo $?\r\n1\r\n[ian@pinguino ~]$ set -u\r\n[ian@pinguino ~]$ test  -o nounset; echo $?\r\n0<\/pre>\n<\/div>\n<p>\u6700\u540e\uff0c<code>-a<\/code> \u548c <code>-o<\/code> \u9009\u9879\u5141\u8bb8\u4f7f\u7528\u903b\u8f91\u8fd0\u7b97\u7b26 AND \u548c OR \u5c06\u8868\u8fbe\u5f0f\u7ec4\u5408\u5728\u4e00\u8d77\u3002\u5355\u76ee\u64cd\u4f5c\u7b26 <code>!<\/code> \u53ef\u4ee5\u4f7f\u6d4b\u8bd5\u7684\u610f\u4e49\u76f8\u53cd\u3002\u53ef\u4ee5\u7528\u62ec\u53f7\u628a\u8868\u8fbe\u5f0f\u5206\u7ec4\uff0c\u8986\u76d6\u9ed8\u8ba4\u7684\u4f18\u5148\u7ea7\u3002\u8bf7\u8bb0\u4f4f shell \u901a\u5e38\u8981\u5728\u5b50 shell \u4e2d\u8fd0\u884c\u62ec\u53f7\u4e2d\u7684\u8868\u8fbe\u5f0f\uff0c\u6240\u4ee5\u9700\u8981\u7528 \\( \u548c \\) \u8f6c\u4e49\u62ec\u53f7\uff0c\u6216\u8005\u628a\u8fd9\u4e9b\u64cd\u4f5c\u7b26\u62ec\u5728\u5355\u5f15\u53f7\u6216\u53cc\u5f15\u53f7\u5185\u3002\u6e05\u5355 4 \u6f14\u793a\u4e86\u6469\u6839\u6cd5\u5219\u5728\u8868\u8fbe\u5f0f\u4e0a\u7684\u5e94\u7528\u3002<\/p>\n<h5 id=\"N1016F\">\u6e05\u5355 4. \u7ec4\u5408\u548c\u5206\u7ec4\u6d4b\u8bd5<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$ test \"a\" != \"$HOME\" -a 3 -ge 4 ; echo $?\r\n1\r\n[ian@pinguino ~]$ [ ! \\( \"a\" = \"$HOME\" -o 3 -lt 4 \\) ]; echo $?\r\n1\r\n[ian@pinguino ~]$ [ ! \\( \"a\" = \"$HOME\" -o '(' 3 -lt 4 ')' \")\" ]; echo $?\r\n1<\/pre>\n<\/div>\n<div class=\"ibm-alternate-rule\"><\/div>\n<p class=\"ibm-ind-link ibm-back-to-top\"><a class=\"ibm-anchor-up-link\" href=\"http:\/\/www.ibm.com\/developerworks\/cn\/linux\/l-bash-test.html#ibm-pcon\">\u56de\u9875\u9996<\/a><\/p>\n<h2 id=\"N10174\">(( \u548c [[<\/h2>\n<p><code>test<\/code> \u547d\u4ee4\u975e\u5e38\u5f3a\u5927\uff0c\u4f46\u662f\u5f88\u96be\u6ee1\u8db3\u5176\u8f6c\u4e49\u9700\u6c42\u4ee5\u53ca\u5b57\u7b26\u4e32\u548c\u7b97\u672f\u6bd4\u8f83\u4e4b\u95f4\u7684\u533a\u522b\u3002\u5e78\u8fd0\u7684\u662f\uff0cbash \u63d0\u4f9b\u4e86\u5176\u4ed6\u4e24\u79cd\u6d4b\u8bd5\u65b9\u5f0f\uff0c\u8fd9\u4e24\u79cd\u65b9\u5f0f\u5bf9\u719f\u6089 C\u3001C++ \u6216 Java\u00ae \u8bed\u6cd5\u7684\u4eba\u6765\u8bf4\u4f1a\u66f4\u81ea\u7136\u4e9b\u3002<\/p>\n<p><code>((\u00a0))<\/code><em>\u590d\u5408\u547d\u4ee4<\/em> \u8ba1\u7b97\u7b97\u672f\u8868\u8fbe\u5f0f\uff0c\u5982\u679c\u8868\u8fbe\u5f0f\u6c42\u503c\u4e3a 0\uff0c\u5219\u8bbe\u7f6e\u9000\u51fa\u72b6\u6001\u4e3a 1\uff1b\u5982\u679c\u6c42\u503c\u4e3a\u975e 0 \u503c\uff0c\u5219\u8bbe\u7f6e\u4e3a 0\u3002\u4e0d\u9700\u8981\u5bf9 <code>((<\/code> \u548c <code>))<\/code> \u4e4b\u95f4\u7684\u64cd\u4f5c\u7b26\u8f6c\u4e49\u3002\u7b97\u672f\u53ea\u5bf9\u6574\u6570\u8fdb\u884c\u3002\u9664 0 \u4f1a\u4ea7\u751f\u9519\u8bef\uff0c\u4f46\u4e0d\u4f1a\u4ea7\u751f\u6ea2\u51fa\u3002\u53ef\u4ee5\u6267\u884c C \u8bed\u8a00\u4e2d\u5e38\u89c1\u7684\u7b97\u672f\u3001\u903b\u8f91\u548c\u4f4d\u64cd\u4f5c\u3002 <code>let<\/code> \u547d\u4ee4\u4e5f\u80fd\u6267\u884c\u4e00\u4e2a\u6216\u591a\u4e2a\u7b97\u672f\u8868\u8fbe\u5f0f\u3002\u5b83\u901a\u5e38\u7528\u6765\u4e3a\u7b97\u672f\u53d8\u91cf\u5206\u914d\u503c\u3002<\/p>\n<h5 id=\"N10191\">\u6e05\u5355 5. \u5206\u914d\u548c\u6d4b\u8bd5\u7b97\u672f\u8868\u8fbe\u5f0f<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$ let x=2 y=2**3 z=y*3;echo $? $x $y $z\r\n0 2 8 24\r\n[ian@pinguino ~]$ (( w=(y\/x) + ( (~ ++x) &amp; 0x0f ) )); echo $? $x $y $w\r\n0 3 8 16\r\n[ian@pinguino ~]$ (( w=(y\/x) + ( (~ ++x) &amp; 0x0f ) )); echo $? $x $y $w\r\n0 4 8 13<\/pre>\n<\/div>\n<p>\u540c\u4f7f\u7528 <code>((\u00a0))<\/code> \u4e00\u6837\uff0c\u5229\u7528\u590d\u5408\u547d\u4ee4 <code>[[\u00a0]]<\/code> \u53ef\u4ee5\u5bf9\u6587\u4ef6\u540d\u548c\u5b57\u7b26\u4e32\u4f7f\u7528\u66f4\u81ea\u7136\u7684\u8bed\u6cd5\u3002\u53ef\u4ee5\u7528\u62ec\u53f7\u548c\u903b\u8f91\u64cd\u4f5c\u7b26\u628a <code>test<\/code> \u547d\u4ee4\u652f\u6301\u7684\u6d4b\u8bd5\u7ec4\u5408\u8d77\u6765\u3002<\/p>\n<h5 id=\"N101A7\">\u6e05\u5355 6. \u4f7f\u7528 [[ \u590d\u5408\u547d\u4ee4<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$ [[ ( -d \"$HOME\" ) &amp;&amp; ( -w \"$HOME\" ) ]] &amp;&amp;  \r\n&gt;  echo \"home is a writable directory\"\r\nhome is a writable directory<\/pre>\n<\/div>\n<p>\u5728\u4f7f\u7528 <code>=<\/code> \u6216 <code>!=<\/code> \u64cd\u4f5c\u7b26\u65f6\uff0c\u590d\u5408\u547d\u4ee4 <code>[[<\/code> \u8fd8\u80fd\u5728\u5b57\u7b26\u4e32\u4e0a\u8fdb\u884c\u6a21\u5f0f\u5339\u914d\u3002\u5339\u914d\u7684\u65b9\u5f0f\u5c31\u50cf\u6e05\u5355 7 \u6240\u793a\u7684\u901a\u914d\u7b26\u5339\u914d\u3002<\/p>\n<h5 id=\"N101B9\">\u6e05\u5355 7. \u7528 [[ \u8fdb\u884c\u901a\u914d\u7b26\u6d4b\u8bd5<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$ [[ \"abc def .d,x--\" == a[abc]*\\ ?d* ]]; echo $?\r\n0\r\n[ian@pinguino ~]$ [[ \"abc def c\" == a[abc]*\\ ?d* ]]; echo $?\r\n1\r\n[ian@pinguino ~]$ [[ \"abc def d,x\" == a[abc]*\\ ?d* ]]; echo $?\r\n1<\/pre>\n<\/div>\n<p>\u751a\u81f3\u8fd8\u53ef\u4ee5\u5728 <code>[[<\/code> \u590d\u5408\u547d\u4ee4\u5185\u6267\u884c\u7b97\u672f\u6d4b\u8bd5\uff0c\u4f46\u662f\u5343\u4e07\u8981\u5c0f\u5fc3\u3002\u9664\u975e\u5728 <code>((<\/code> \u590d\u5408\u547d\u4ee4\u5185\uff0c\u5426\u5219 <code>&lt;<\/code> \u548c <code>&gt;<\/code> \u64cd\u4f5c\u7b26\u4f1a\u628a\u64cd\u4f5c\u6570\u5f53\u6210\u5b57\u7b26\u4e32\u6bd4\u8f83\u5e76\u5728\u5f53\u524d\u6392\u5e8f\u5e8f\u5217\u4e2d\u6d4b\u8bd5\u5b83\u4eec\u7684\u987a\u5e8f\u3002\u6e05\u5355 8 \u7528\u4e00\u4e9b\u793a\u4f8b\u6f14\u793a\u4e86\u8fd9\u4e00\u70b9\u3002<\/p>\n<h5 id=\"N101CE\">\u6e05\u5355 8. \u7528 [[ \u5305\u542b\u7b97\u672f\u6d4b\u8bd5<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$ [[ \"abc def d,x\" == a[abc]*\\ ?d* || (( 3 &gt; 2 )) ]]; echo $?\r\n0\r\n[ian@pinguino ~]$ [[ \"abc def d,x\" == a[abc]*\\ ?d* || 3 -gt 2 ]]; echo $?\r\n0\r\n[ian@pinguino ~]$ [[ \"abc def d,x\" == a[abc]*\\ ?d* || 3 &gt; 2 ]]; echo $?\r\n0\r\n[ian@pinguino ~]$ [[ \"abc def d,x\" == a[abc]*\\ ?d* || a &gt; 2 ]]; echo $?\r\n0\r\n[ian@pinguino ~]$ [[ \"abc def d,x\" == a[abc]*\\ ?d* || a -gt 2 ]]; echo $?\r\n-bash: a: unbound variable<\/pre>\n<\/div>\n<div class=\"ibm-alternate-rule\"><\/div>\n<p class=\"ibm-ind-link ibm-back-to-top\"><a class=\"ibm-anchor-up-link\" href=\"http:\/\/www.ibm.com\/developerworks\/cn\/linux\/l-bash-test.html#ibm-pcon\">\u56de\u9875\u9996<\/a><\/p>\n<h2 id=\"N101D3\">\u6761\u4ef6\u6d4b\u8bd5<\/h2>\n<p>\u867d\u7136\u4f7f\u7528\u4ee5\u4e0a\u7684\u6d4b\u8bd5\u548c <code>&amp;&amp;<\/code>\u3001 <code>||<\/code> \u63a7\u5236\u64cd\u4f5c\u7b26\u80fd\u5b9e\u73b0\u8bb8\u591a\u7f16\u7a0b\uff0c\u4f46 bash \u8fd8\u5305\u542b\u4e86\u66f4\u719f\u6089\u7684 \u201cif, then, else\u201d \u548c case \u7ed3\u6784\u3002\u5b66\u4e60\u5b8c\u8fd9\u4e9b\u4e4b\u540e\uff0c\u5c06\u5b66\u4e60\u5faa\u73af\u7ed3\u6784\uff0c\u8fd9\u6837\u60a8\u7684\u5de5\u5177\u7bb1\u5c06\u771f\u6b63\u5f97\u5230\u6269\u5c55\u3002<\/p>\n<h3 id=\"N101DF\">If\u3001then\u3001else \u8bed\u53e5<\/h3>\n<p>bash \u7684 <code>if<\/code> \u547d\u4ee4\u662f\u4e2a\u590d\u5408\u547d\u4ee4\uff0c\u5b83\u6d4b\u8bd5\u4e00\u4e2a\u6d4b\u8bd5\u6216\u547d\u4ee4\uff08<code>$?<\/code>\uff09\u7684\u8fd4\u56de\u503c\uff0c\u5e76\u6839\u636e\u8fd4\u56de\u503c\u4e3a True\uff080\uff09\u6216 False\uff08\u4e0d\u4e3a 0\uff09\u8fdb\u884c\u5206\u652f\u3002\u867d\u7136\u4e0a\u9762\u7684\u6d4b\u8bd5\u53ea\u8fd4\u56de 0 \u6216 1 \u503c\uff0c\u4f46\u547d\u4ee4\u53ef\u80fd\u8fd4\u56de\u5176\u4ed6\u503c\u3002\u8bf7\u53c2\u9605 <a href=\"http:\/\/www.ibm.com\/developerworks\/cn\/edu\/l-dw-linux-lpic1109-i.html\">LPI 102 \u8003\u8bd5\u51c6\u5907\uff0c\u4e3b\u9898 109: Shell\u3001\u811a\u672c\u3001\u7f16\u7a0b\u548c\u7f16\u8bd1<\/a> \u6559\u7a0b\u5b66\u4e60\u8fd9\u65b9\u9762\u7684\u66f4\u591a\u5185\u5bb9\u3002<\/p>\n<p>Bash \u4e2d\u7684 <code>if<\/code> \u547d\u4ee4\u6709\u4e00\u4e2a <code>then<\/code> \u5b50\u53e5\uff0c\u5b50\u53e5\u4e2d\u5305\u542b\u6d4b\u8bd5\u6216\u547d\u4ee4\u8fd4\u56de 0 \u65f6\u8981\u6267\u884c\u7684\u547d\u4ee4\u5217\u8868\uff0c\u53ef\u4ee5\u6709\u4e00\u4e2a\u6216\u591a\u4e2a\u53ef\u9009\u7684 <code>elif<\/code> \u5b50\u53e5\uff0c\u6bcf\u4e2a\u5b50\u53e5\u53ef\u6267\u884c\u9644\u52a0\u7684\u6d4b\u8bd5\u548c\u4e00\u4e2a <code>then<\/code> \u5b50\u53e5\uff0c\u5b50\u53e5\u4e2d\u53c8\u5e26\u6709\u76f8\u5173\u7684\u547d\u4ee4\u5217\u8868\uff0c\u6700\u540e\u662f\u53ef\u9009\u7684 <code>else<\/code> \u5b50\u53e5\u53ca\u547d\u4ee4\u5217\u8868\uff0c\u5728\u524d\u9762\u7684\u6d4b\u8bd5\u6216 <code>elif<\/code> \u5b50\u53e5\u4e2d\u7684\u6240\u6709\u6d4b\u8bd5\u90fd\u4e0d\u4e3a\u771f\u7684\u65f6\u5019\u6267\u884c\uff0c\u6700\u540e\u4f7f\u7528 <code>fi<\/code> \u6807\u8bb0\u8868\u793a\u8be5\u7ed3\u6784\u7ed3\u675f\u3002<\/p>\n<p>\u4f7f\u7528\u8fc4\u4eca\u4e3a\u6b62\u5b66\u5230\u7684\u4e1c\u897f\uff0c\u73b0\u5728\u80fd\u591f\u6784\u5efa\u7b80\u5355\u7684\u8ba1\u7b97\u5668\u6765\u8ba1\u7b97\u7b97\u672f\u8868\u8fbe\u5f0f\uff0c\u5982\u6e05\u5355 9 \u6240\u793a\uff1a<\/p>\n<h5 id=\"N1020A\">\u6e05\u5355 9. \u7528 if\u3001then\u3001else \u8ba1\u7b97\u8868\u8fbe\u5f0f<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$ function mycalc ()\r\n&gt; {\r\n&gt;   local x\r\n&gt;   if [ $# -lt 1 ]; then\r\n&gt;     echo \"This function evaluates arithmetic for you if you give it some\"\r\n&gt;   elif (( $* )); then\r\n&gt;     let x=\"$*\"\r\n&gt;     echo \"$* = $x\"\r\n&gt;   else\r\n&gt;     echo \"$* = 0 or is not an arithmetic expression\"\r\n&gt;   fi\r\n&gt; }\r\n[ian@pinguino ~]$ mycalc 3 + 4\r\n3 + 4 = 7\r\n[ian@pinguino ~]$ mycalc 3 + 4**3\r\n3 + 4**3 = 67\r\n[ian@pinguino ~]$ mycalc 3 + (4**3 \/2)\r\n-bash: syntax error near unexpected token `('\r\n[ian@pinguino ~]$ mycalc 3 + \"(4**3 \/2)\"\r\n3 + (4**3 \/2) = 35\r\n[ian@pinguino ~]$ mycalc xyz\r\nxyz = 0 or is not an arithmetic expression\r\n[ian@pinguino ~]$ mycalc xyz + 3 + \"(4**3 \/2)\" + abc\r\nxyz + 3 + (4**3 \/2) + abc = 35<\/pre>\n<\/div>\n<p>\u8fd9\u4e2a\u8ba1\u7b97\u5668\u5229\u7528 <code>local<\/code> \u8bed\u53e5\u5c06 x \u58f0\u660e\u4e3a\u5c40\u90e8\u53d8\u91cf\uff0c\u53ea\u80fd\u5728 <code>mycalc<\/code> \u51fd\u6570\u7684\u8303\u56f4\u5185\u4f7f\u7528\u3002<code>let<\/code> \u51fd\u6570\u5177\u6709\u51e0\u4e2a\u53ef\u7528\u7684\u9009\u9879\uff0c\u53ef\u4ee5\u6267\u884c\u4e0e\u5b83\u5bc6\u5207\u5173\u8054\u7684 <code>declare<\/code> \u51fd\u6570\u3002\u8bf7\u53c2\u8003 bash \u624b\u518c\u6216\u4f7f\u7528 <code>help\u00a0let<\/code> \u83b7\u5f97\u66f4\u591a\u4fe1\u606f\u3002<\/p>\n<p>\u5982\u6e05\u5355 9 \u6240\u793a\uff0c\u9700\u8981\u786e\u4fdd\u5728\u8868\u8fbe\u5f0f\u4f7f\u7528 shell \u5143\u5b57\u7b26 \u2014\u2014 \u4f8b\u5982(\u3001)\u3001*\u3001&gt; \u548c &lt; \u65f6 \u2014\u2014 \u6b63\u786e\u5730\u5bf9\u8868\u8fbe\u5f0f\u8f6c\u4e49\u3002\u65e0\u8bba\u5982\u4f55\uff0c\u73b0\u5728\u6709\u4e86\u4e00\u4e2a\u975e\u5e38\u65b9\u4fbf\u7684\u5c0f\u8ba1\u7b97\u5668\uff0c\u53ef\u4ee5\u50cf shell \u90a3\u6837\u8fdb\u884c\u7b97\u672f\u8ba1\u7b97\u3002<\/p>\n<p>\u5728\u6e05\u5355 9 \u4e2d\u53ef\u80fd\u6ce8\u610f\u5230 <code>else<\/code> \u5b50\u53e5\u548c\u6700\u540e\u7684\u4e24\u4e2a\u793a\u4f8b\u3002\u53ef\u4ee5\u770b\u5230\uff0c\u628a <code>xyz<\/code> \u4f20\u9012\u7ed9 mycalc \u5e76\u6ca1\u6709\u9519\u8bef\uff0c\u4f46\u8ba1\u7b97\u7ed3\u679c\u4e3a 0\u3002\u8fd9\u4e2a\u51fd\u6570\u8fd8\u4e0d\u591f\u7075\u5de7\uff0c\u4e0d\u80fd\u533a\u5206\u6700\u540e\u4f7f\u7528\u7684\u793a\u4f8b\u4e2d\u7684\u5b57\u7b26\u503c\uff0c\u6240\u4ee5\u4e0d\u80fd\u8b66\u544a\u7528\u6237\u3002\u53ef\u4ee5\u4f7f\u7528\u5b57\u7b26\u4e32\u6a21\u5f0f\u5339\u914d\u6d4b\u8bd5\uff08\u4f8b\u5982<br \/>\n<code>[[ ! (\"$*\" == *[a-zA-Z]* ]]<\/code><br \/>\n\uff0c\u6216\u4f7f\u7528\u9002\u5408\u81ea\u5df1\u8303\u56f4\u7684\u5f62\u5f0f\uff09\u6d88\u9664\u5305\u542b\u5b57\u6bcd\u8868\u5b57\u7b26\u7684\u8868\u8fbe\u5f0f\uff0c\u4f46\u662f\u8fd9\u4f1a\u59a8\u788d\u5728\u8f93\u5165\u4e2d\u4f7f\u7528 16 \u8fdb\u5236\u6807\u8bb0\uff0c\u56e0\u4e3a\u4f7f\u7528 16 \u8fdb\u5236\u6807\u8bb0\u65f6\u53ef\u80fd\u8981\u7528 0x0f \u8868\u793a 15\u3002\u5b9e\u9645\u4e0a\uff0cshell \u5141\u8bb8\u7684\u57fa\u6570\u6700\u9ad8\u4e3a 64\uff08\u4f7f\u7528 <code><em>base<\/em>#<em>value<\/em><\/code> \u6807\u8bb0\uff09\uff0c\u6240\u4ee5\u53ef\u4ee5\u5728\u8f93\u5165\u4e2d\u52a0\u5165 _ \u548c @ \u5408\u6cd5\u5730\u4f7f\u7528\u4efb\u4f55\u5b57\u6bcd\u8868\u5b57\u7b26\u30028 \u8fdb\u5236\u548c 16 \u8fdb\u5236\u4f7f\u7528\u5e38\u7528\u7684\u6807\u8bb0\u65b9\u5f0f\uff0c\u5f00\u5934\u4e3a 0 \u8868\u793a\u516b\u8fdb\u5236\uff0c\u5f00\u5934\u4e3a 0x \u6216 0X \u8868\u793a 16 \u8fdb\u5236\u3002\u6e05\u5355 10 \u663e\u793a\u4e86\u4e00\u4e9b\u793a\u4f8b\u3002<\/p>\n<h5 id=\"N1023A\">\u6e05\u5355 10. \u7528\u4e0d\u540c\u7684\u57fa\u6570\u8fdb\u884c\u8ba1\u7b97<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$ mycalc 015\r\n015 = 13\r\n[ian@pinguino ~]$ mycalc 0xff\r\n0xff = 255\r\n[ian@pinguino ~]$ mycalc 29#37\r\n29#37 = 94\r\n[ian@pinguino ~]$ mycalc 64#1az\r\n64#1az = 4771\r\n[ian@pinguino ~]$ mycalc 64#1azA\r\n64#1azA = 305380\r\n[ian@pinguino ~]$ mycalc 64#1azA_@\r\n64#1azA_@ = 1250840574\r\n[ian@pinguino ~]$ mycalc 64#1az*64**3 + 64#A_@\r\n64#1az*64**3 + 64#A_@ = 1250840574<\/pre>\n<\/div>\n<p>\u5bf9\u8f93\u5165\u8fdb\u884c\u7684\u989d\u5916\u5904\u7406\u8d85\u51fa\u4e86\u672c\u6280\u5de7\u7684\u8303\u56f4\uff0c\u6240\u4ee5\u8bf7\u5c0f\u5fc3\u4f7f\u7528\u8fd9\u4e2a\u8ba1\u7b97\u5668\u3002<\/p>\n<p><code>elif<\/code> \u8bed\u53e5\u975e\u5e38\u65b9\u4fbf\u3002\u5b83\u5141\u8bb8\u7b80\u5316\u7f29\u8fdb\uff0c\u4ece\u800c\u6709\u52a9\u4e8e\u811a\u672c\u7f16\u5199\u3002\u5728\u6e05\u5355 11 \u4e2d\u53ef\u80fd\u4f1a\u5bf9 <code>type<\/code> \u547d\u4ee4\u5728 <code>mycalc<\/code> \u51fd\u6570\u4e2d\u7684\u8f93\u51fa\u611f\u5230\u60ca\u8bb6\u3002<\/p>\n<h5 id=\"N1024D\">\u6e05\u5355 11. Type mycalc<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$ type mycalc\r\nmycalc is a function\r\nmycalc ()\r\n{\r\n    local x;\r\n    if [ $# -lt 1 ]; then\r\n        echo \"This function evaluates arithmetic for you if you give it some\";\r\n    else\r\n        if (( $* )); then\r\n            let x=\"$*\";\r\n            echo \"$* = $x\";\r\n        else\r\n            echo \"$* = 0 or is not an arithmetic expression\";\r\n        fi;\r\n    fi\r\n}<\/pre>\n<\/div>\n<p>\u5f53\u7136\uff0c\u4e5f\u53ef\u4ee5\u53ea\u7528 <code>$((\u00a0<em>\u8868\u8fbe\u5f0f<\/em>\u00a0))<\/code> \u548c <code>echo <\/code> \u547d\u4ee4\u8fdb\u884c shell \u7b97\u672f\u8fd0\u7b97\uff0c\u5982\u6e05\u5355 12 \u6240\u793a\u3002\u8fd9\u6837\u5c31\u4e0d\u5fc5\u5b66\u4e60\u5173\u4e8e\u51fd\u6570\u6216\u6d4b\u8bd5\u7684\u4efb\u4f55\u5185\u5bb9\uff0c\u4f46\u662f\u8bf7\u6ce8\u610f shell \u4e0d\u4f1a\u89e3\u91ca\u5143\u5b57\u7b26\uff0c\u4f8b\u5982 *\uff0c\u56e0\u6b64\u5143\u5b57\u7b26\u4e0d\u80fd\u5728 <code>((\u00a0<em>\u8868\u8fbe\u5f0f<\/em>\u00a0))<\/code> \u6216 <code>[[\u00a0<em>\u8868\u8fbe\u5f0f<\/em>\u00a0]]<\/code> \u4e2d\u90a3\u6837\u6b63\u5e38\u53d1\u6325\u4f5c\u7528\u3002<\/p>\n<h5 id=\"N10271\">\u6e05\u5355 12. \u5728 shell \u4e2d\u7528 echo \u548c $(( )) \u76f4\u63a5\u8fdb\u884c\u8ba1\u7b97<\/h5>\n<div class=\"codesection\">\n<pre class=\"displaycode\">[ian@pinguino ~]$  echo $((3 + (4**3 \/2)))\r\n35<\/pre>\n<\/div>\n<div class=\"ibm-alternate-rule\"><\/div>\n<p class=\"ibm-ind-link ibm-back-to-top\"><a class=\"ibm-anchor-up-link\" href=\"http:\/\/www.ibm.com\/developerworks\/cn\/linux\/l-bash-test.html#ibm-pcon\">\u56de\u9875\u9996<\/a><\/p>\n<h2 id=\"N10276\">\u7ed3\u675f\u8bed<\/h2>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>developerWorks \u4e2d\u56fd \u6280\u672f\u4e3b\u9898 Linux \u6587\u6863\u5e93 Linux \u6280 &hellip; <a href=\"https:\/\/blog.zhenglei.net\/?p=255290\">\u7ee7\u7eed\u9605\u8bfb <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[242,44],"class_list":["post-255290","post","type-post","status-publish","format-standard","hentry","category-linux","tag-bash","tag-shell"],"_links":{"self":[{"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=\/wp\/v2\/posts\/255290","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=255290"}],"version-history":[{"count":1,"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=\/wp\/v2\/posts\/255290\/revisions"}],"predecessor-version":[{"id":255291,"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=\/wp\/v2\/posts\/255290\/revisions\/255291"}],"wp:attachment":[{"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=255290"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=255290"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=255290"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}