{"id":3650,"date":"2017-10-28T13:30:07","date_gmt":"2017-10-28T05:30:07","guid":{"rendered":"https:\/\/ixyzero.com\/blog\/?p=3650"},"modified":"2017-10-28T13:30:07","modified_gmt":"2017-10-28T05:30:07","slug":"bash%e4%b8%ad%e7%9a%84%e5%ad%97%e7%ac%a6%e4%b8%b2%e4%b8%8e%e9%bb%98%e8%ae%a4%e5%80%bc","status":"publish","type":"post","link":"https:\/\/ixyzero.com\/blog\/archives\/3650.html","title":{"rendered":"Bash\u4e2d\u7684\u5b57\u7b26\u4e32\u4e0e\u9ed8\u8ba4\u503c"},"content":{"rendered":"<p>=Start=<\/p>\n<h4>\u7f18\u7531\uff1a<\/h4>\n<p>\u633a\u6709\u7528\u7684\u4e00\u4e2a\u77e5\u8bc6\u70b9\uff0c\u867d\u7136\u4e5f\u6709\u66ff\u4ee3\u7684\u65b9\u6cd5\uff08\u53ea\u662f\u6ca1\u90a3\u4e48\u4f18\u96c5\uff09\uff0c\u4f46\u662f\u591a\u603b\u7ed3\u4e00\u4e0b\uff0c\u5f80\u6700\u4f73\u5b9e\u8df5\u65b9\u5411\u9760\u4e5f\u662f\u6781\u597d\u7684\u3002<\/p>\n<h4>\u6b63\u6587\uff1a<\/h4>\n<h5>\u53c2\u8003\u89e3\u7b54\uff1a<\/h5>\n<ul>\n<li>\u603b\u7ed3\uff1a\u4f7f\u7528 `${var:-default_value}` \u7684\u65b9\u5f0f\uff01<\/li>\n<\/ul>\n<pre class=\"lang:default decode:true\">#!\/bin\/bash\r\n# set -x\r\nexport PATH=\/usr\/local\/bin:\/bin:\/usr\/bin:\/sbin:\/usr\/sbin\/:\/usr\/local\/sbin\r\n\r\nwp_version=$(ls -lt | grep 'this is not a valid search condition')\r\necho \"\\$wp_version = $wp_version\"\r\necho \"\\${wp_version:-unknown} = ${wp_version:-unknown}\"\r\n# echo \"\\${wp_version:?unknown} = ${wp_version:?unknown}\"\t# [\u62a5\u9519\u9000\u51fa]line 8: wp_version: unknown\r\necho\r\n\r\nfunction test_arg()\t#\u5982\u679c\u6ca1\u6709\u7ed9\u51fd\u6570\u4f20\u53c2\uff0c\u5219 $1 \u5e94\u8be5\u5c31\u662f\u672a\u5b9a\u4e49\u7684\r\n{\r\n\techo \"$#\"\r\n\tlocal arg1=\"$1\"\r\n\techo \"\\$arg1 = $arg1\"\r\n\t\r\n\tlocal arg1_default=\"${1:-unknown}\"\r\n\techo \"\\$arg1_default = $arg1_default\"\r\n\techo \"\\${1:-unknown} = ${1:-unknown}\"\r\n\r\n\t# local arg1_default2=\"${1:?unknown}\"\t# line 21: 1: unknown\r\n\t# echo \"\\$arg1_default2 = $arg1_default2\"\r\n\t# echo \"\\${1:?unknown} = ${1:?unknown}\"\r\n}\r\ntest_arg aabbcc\r\ntest_arg\r\n\r\nfunction test_arg2()\t#\u5982\u679c\u6ca1\u6709\u7ed9\u51fd\u6570\u4f20\u53c2\uff0c\u5219 $1 \u5c31\u662f\u672a\u5b9a\u4e49\u7684\r\n{\r\n\techo \"$#\"\r\n\tif [ $# -gt 0 ]; then\r\n\t\targ1=\"$1\"\r\n\telse\r\n\t\targ1=\"x\"\t#\u8fd9\u91cc\u53ea\u8981\u7ed9 arg1 \u4e00\u4e2a\u9ed8\u8ba4'\u975e\u7a7a'\u503c\uff0c\u5219\u540e\u9762\u7684 line42 \u5c31\u4e0d\u4f1a\u62a5\u9519\r\n\tfi\r\n\techo \"\\$arg1 = $arg1\"\r\n\t\r\n\tlocal arg1_default=\"${arg1:-unknown}\"\r\n\techo \"\\$arg1_default = $arg1_default\"\r\n\techo \"\\${arg1:-unknown} = ${arg1:-unknown}\"\r\n\r\n\tlocal arg1_default2=\"${arg1:?unknown}\"\t# line 42: arg1: unknown\r\n\techo \"\\$arg1_default2 = $arg1_default2\"\r\n\techo \"\\${arg1:?unknown} = ${arg1:?unknown}\"\r\n}\r\necho\r\ntest_arg2 aabbcc\r\ntest_arg2\r\n\r\n# \u7ed3\u8bba\uff1a\u4f7f\u7528 ${var:-default_value} \u4ee5\u5728\u8fbe\u5230\u76ee\u7684\u7684\u540c\u65f6\u907f\u514d\u9519\u8bef<\/pre>\n<h5>\u53c2\u8003\u94fe\u63a5\uff1a<\/h5>\n<ul>\n<li><a href=\"http:\/\/www.cnblogs.com\/fhefh\/archive\/2011\/04\/22\/2024750.html\">linux bash shell\u4e4b\u53d8\u91cf\u66ff\u6362\uff1a:=\u53e5\u6cd5\u3001=\u53e5\u6cd5\u3001:-\u53e5\u6cd5\u3001-\u53e5\u6cd5\u3001=?\u53e5\u6cd5\u3001?\u53e5\u6cd5\u3001:+\u53e5\u6cd5\u3001+\u53e5\u6cd5<\/a><\/li>\n<li><a href=\"http:\/\/www.cnblogs.com\/chengmo\/archive\/2010\/10\/02\/1841355.html\">linux shell \u5b57\u7b26\u4e32\u64cd\u4f5c\uff08\u957f\u5ea6\uff0c\u67e5\u627e\uff0c\u66ff\u6362\uff09\u8be6\u89e3<\/a><\/li>\n<li><a href=\"http:\/\/www.mojidong.com\/linux\/2012\/09\/08\/shell-set-default-value\/\">shell\u4e2d\u7ed9\u53d8\u91cf\u8bbe\u7f6e\u9ed8\u8ba4\u503c<\/a><\/li>\n<li><a href=\"http:\/\/linuxnote.blog.51cto.com\/9876511\/1641172\">Linux Shell\u4e4b\u4e09 \u9ad8\u7ea7\u53d8\u91cf\u53ca\u5b57\u7b26\u4e32<\/a><\/li>\n<li><a href=\"http:\/\/metman.info\/blog\/2014\/11\/23\/shellbian-cheng-xue-xi-bi-ji-%3Abian-liang-pian-er\/\">Shell\u7f16\u7a0b\u5b66\u4e60\u7b14\u8bb0\uff1a\u53d8\u91cf\u7bc7(\u4e8c)<\/a><\/li>\n<li><a href=\"https:\/\/www.ibm.com\/developerworks\/cn\/linux\/l-bash-parameters.html#N1020F\">Bash \u53c2\u6570\u548c\u53c2\u6570\u6269\u5c55<\/a><\/li>\n<\/ul>\n<p>=END=<\/p>\n","protected":false},"excerpt":{"rendered":"<p>=Start= \u7f18\u7531\uff1a \u633a\u6709\u7528\u7684\u4e00\u4e2a\u77e5\u8bc6\u70b9\uff0c\u867d\u7136\u4e5f\u6709\u66ff\u4ee3\u7684\u65b9\u6cd5\uff08\u53ea\u662f\u6ca1\u90a3\u4e48\u4f18\u96c5\uff09\uff0c\u4f46\u662f\u591a\u603b\u7ed3\u4e00\u4e0b\uff0c\u5f80\u6700\u4f73\u5b9e\u8df5\u65b9 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23,11,7],"tags":[83,65],"class_list":["post-3650","post","type-post","status-publish","format-standard","hentry","category-knowledgebase-2","category-linux","category-programing","tag-bash","tag-shell"],"views":3864,"_links":{"self":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/3650","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\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/comments?post=3650"}],"version-history":[{"count":1,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/3650\/revisions"}],"predecessor-version":[{"id":3651,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/3650\/revisions\/3651"}],"wp:attachment":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/media?parent=3650"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/categories?post=3650"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/tags?post=3650"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}