{"id":276,"date":"2017-12-20T10:20:36","date_gmt":"2017-12-20T10:20:36","guid":{"rendered":"http:\/\/www.liutianfeng.com\/?p=276"},"modified":"2022-01-21T06:23:06","modified_gmt":"2022-01-21T06:23:06","slug":"bash%e4%b8%ad%e7%9a%84%e7%ae%97%e6%9c%af%e8%bf%90%e7%ae%97","status":"publish","type":"post","link":"https:\/\/www.liutianfeng.com\/?p=276","title":{"rendered":"bash\u4e2d\u7684\u7b97\u672f\u8fd0\u7b97 – $(()) $[] let expr bc typeset"},"content":{"rendered":"

\u57fa\u672c\u4ecb\u7ecd\uff1a<\/p>\n

\u5728\u7b97\u672f\u8ba1\u7b97\u4e2d\uff0c\uff08$(()) $[] let expr bc\uff09\u8fd9\u4e9b\u65b9\u6cd5\u90fd\u80fd\u5b9e\u73b0\u3002\u591a\u6570\u7684\u65b9\u6cd5\u5b9e\u73b0\u65b9\u6cd5\u7c7b\u4f3c\uff0c\u6709\u7684\u6709\u4e00\u4e9b\u7279\u6b8a\u7684\u529f\u80fd\uff08\u5982expr\uff09\uff1b\u53ea\u6709bc\u53ef\u4ee5\u8ba1\u7b97\u6d6e\u70b9\u6570\uff0c\u5176\u4ed6\u90fd\u662f\u6574\u6570\u7684\u8fd0\u7b97<\/strong><\/span>\u3002<\/p>\n

bash\u4e2d\u9ed8\u8ba4\u5c06\u6240\u6709\u7684\u53d8\u91cf\u5f53\u505a\u5b57\u7b26\u4e32\u6765\u5904\u7406\uff0c\u5982\u4e0b\uff1a<\/p>\n

# a=2\r\n# b=3\r\n# c=$a+$b\r\n# echo $c\r\n2+3<\/code><\/pre>\n
\u5982\u679c\u8981\u8fdb\u884c\u7b97\u672f\u8fd0\u7b97\uff0c\u6709\u4ee5\u4e0b\u56db\u79cd\u65b9\u6cd5\uff08\u5e38\u7528\u524d\u4e09\u79cd\uff09\uff1a<\/p>\n
\u65b9\u6cd5\u4e00\uff1alet\u5f15\u5bfc\u7684\u7b97\u672f\u8868\u8fbe\u5f0f\r\n# let c=$a+$b\r\n# echo $c\r\n5\r\n# let \"c=a+b\"    \/\/ \u5982\u679c\u7528\u5f15\u53f7\uff0c\u5219\u76f4\u63a5\u5168\u90e8\u4e0d\u7528\u52a0$,\u76f4\u63a5\u7528\u53d8\u91cf\u540d\u79f0\u5373\u53ef\u8fdb\u884c\u8fd0\u7b97\r\n\u65b9\u6cd5\u4e8c\uff1a$[\u7b97\u672f\u8868\u8fbe\u5f0f]\r\n# d=$[$a+$b]\r\n# echo $d\r\n5\r\n\u65b9\u6cd5\u4e09\uff1a$((\u7b97\u672f\u8868\u8fbe\u5f0f))\r\n# e=$(($a*$b))\r\n# echo $e\r\n6\r\n\u65b9\u6cd5\u56db\uff1a\u7528expr\u547d\u4ee4\uff0c\u7b97\u672f\u8fd0\u7b97\u7b26\u4e4b\u95f4\u5fc5\u987b\u8981\u6709\u7a7a\u683c<\/span><\/strong>\uff0c\u4e14\u8981\u7528\u5230\u547d\u4ee4\u5f15\u7528``,$()\r\n# f=$(expr $b - $a) && echo $f\r\n1\r\n# f=`expr $b - $a` && echo $f\r\n1\r\n# f=`expr $b-$a` && echo $f    \/\/\u4e0d\u52a0\u7a7a\u683c\u5c31\u53d8\u6210\u5b57\u7b26\u4e32\r\n3-2\r\n\r\nexpr\u7684\u7279\u6b8a\u7528\u6cd5\uff1a\r\nexpr\u6709\u4e00\u4e9b\u81ea\u5e26\u7684\u65b9\u6cd5\uff0c\u5173\u952e\u65f6\u5019\u80fd\u8d77\u5230\u6bd4\u8f83\u65b9\u4fbf\u7684\u4f5c\u7528\u3002\r\n#\u00a0\u8ba1\u7b97\u5b57\u7b26\u4e32\u957f\u5ea6\r\n> echo `expr length \"Hello, Lius...\"`\r\n14\r\n#\u00a0\u5b57\u7b26\u4e32\u5339\u914d\uff1a\u5b57\u7b26\u4e32\u00a0:\u00a0REGEXP\r\n> vim aaa.sh\r\n#!\/bin\/bash\r\nif expr $1 : \".*\\.pub\" &> \/dev\/null; then\r\n    echo Yes\r\nelse\r\n    echo No\r\nfi\r\n\r\n> bash\u00a0aaa.sh\u00a0lius.pub\r\nYes\r\n> bash\u00a0aaa.sh\u00a0lius.sh\r\nNo\r\n\r\n\u65b9\u6cd5\u4e94\uff1abc\r\n#\u00a0\u4ea4\u4e92\u5f0f\r\n # bc\r\nbc 1.06.95\r\nCopyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.\r\nThis is free software with ABSOLUTELY NO WARRANTY.\r\nFor details type `warranty'. \r\n1+2\r\n3\r\n\r\n#\u00a0\u7ba1\u9053\u7684\u5f62\u5f0f\u5b9e\u73b0\r\n# echo \"1+2*4\" |bc\r\n9\r\n# echo \"scale=2; 1+2*4\/3\" |bc\r\n3.66\r\n\r\n# \u663e\u793a\u5c0f\u6570\u70b9\u524d\u9762\u76840\r\necho \"scale=2; 2.5\/20\" |bc |awk '{printf \"%.2f\", $0}'\r\n#\u00a0\u8fdb\u5236\u8f6c\u6362\r\n# echo \"obase=16; 26\" |bc\r\n1A\r\n# echo \"obase=2; 26\" |bc\r\n11010\r\n\r\n\u65b9\u6cd5\u516d\uff1atypeset\uff0c\u5f88\u5c11\u7528\r\n# typeset -i A=3 B=2 C\r\n# C=A+B\r\n# echo $C\r\n5<\/code><\/pre>\n
\u5728\u5224\u65ad\u6761\u4ef6\u4e2d\uff0c\u76ee\u524d\u8fd8\u6ca1\u6709\u9047\u5230let\u7684\u7528\u6b66\u4e4b\u5730\uff1a<\/p>\n
\u5224\u65ad\u6761\u4ef6\uff1a\r\n# if test $[$a+$b] -eq 5; then echo \"Yes\"; else echo \"No\"; fi\r\nYes\r\n# if test `expr $a + $b` -eq 5; then echo \"Yes\"; else echo \"No\"; fi\r\nYes<\/code><\/pre>\n
\u8f6c\u8f7d\u8bf7\u6ce8\u660e\uff1aliutianfeng.com<\/a> » bash\u4e2d\u7684\u7b97\u672f\u8fd0\u7b97 – $(()) $[] let expr bc typeset<\/a><\/p>","protected":false},"excerpt":{"rendered":"
\u57fa\u672c\u4ecb\u7ecd\uff1a \u5728\u7b97\u672f\u8ba1\u7b97\u4e2d\uff0c\uff08$(()) $[] let expr bc\uff09\u8fd9\u4e9b\u65b9\u6cd5\u90fd\u80fd\u5b9e\u73b0\u3002\u591a\u6570\u7684\u65b9\u6cd5\u5b9e\u73b0\u65b9\u6cd5\u7c7b […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[31],"tags":[],"_links":{"self":[{"href":"https:\/\/www.liutianfeng.com\/index.php?rest_route=\/wp\/v2\/posts\/276"}],"collection":[{"href":"https:\/\/www.liutianfeng.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.liutianfeng.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.liutianfeng.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.liutianfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=276"}],"version-history":[{"count":8,"href":"https:\/\/www.liutianfeng.com\/index.php?rest_route=\/wp\/v2\/posts\/276\/revisions"}],"predecessor-version":[{"id":1158,"href":"https:\/\/www.liutianfeng.com\/index.php?rest_route=\/wp\/v2\/posts\/276\/revisions\/1158"}],"wp:attachment":[{"href":"https:\/\/www.liutianfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=276"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.liutianfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=276"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.liutianfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=276"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}