x=\"2\" \n\necho $x <\/code><\/pre>\n\n\n\n![\"\"](\"http:\/\/fanaticboy.com\/wp-content\/uploads\/2022\/08\/image.png\")
<\/figure>\n\n\n\n\u4e0a\u9762\u7684\u6587\u4ef6\u91cc\u9762\u7684echo\u662f\u7528\u4e8e\u8f93\u51fa\u7684\uff0c\u53d8\u91cf\u672c\u8eab\u7684\u503c\u9700\u8981\u7528\u5230$<\/p>\n\n\n\n
<\/p>\n\n\n\n
\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u53d8\u91cf\u540d\u548c\u7b49\u53f7\u4e4b\u95f4\u4e0d\u80fd\u6709\u7a7a\u683c! \u5426\u5219\u4f1a\u88abShell\u89e3\u91ca\u6210\u547d\u4ee4\u548c\u547d\u4ee4\u884c\u53c2\u6570\u3002 \u540c\u65f6\uff0c\u53d8\u91cf\u540d\u7684\u547d\u540d\u987b\u9075\u5faa\u5982\u4e0b\u89c4\u5219\uff1a<\/p>\n\n\n\n
\u9996\u4e2a\u5b57\u7b26\u5fc5\u987b\u4e3a\u5b57\u6bcd\uff08a-z\uff0cA-Z\uff09\u3002
\u4e2d\u95f4\u4e0d\u80fd\u6709\u7a7a\u683c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e0b\u5212\u7ebf\uff08_\uff09\u3002
\u4e0d\u80fd\u4f7f\u7528\u6807\u70b9\u7b26\u53f7\u3002
\u4e0d\u80fd\u4f7f\u7528bash\u91cc\u7684\u5173\u952e\u5b57\uff08\u53ef\u7528help\u547d\u4ee4\u67e5\u770b\u4fdd\u7559\u5173\u952e\u5b57\uff09\u3002<\/p><\/blockquote>\n\n\n\n
\u8bf4\u51e0\u4e2a\u5e38\u7528\u7684\u529f\u80fd<\/p>\n\n\n\n
\u4e00\u3001\u83b7\u53d6\u5b57\u7b26\u4e32\u7684\u957f\u5ea6\uff0c\u7528#\u7b26\u53f7\u83b7\u53d6\uff0c\u5177\u4f53\u770b\u4ee3\u7801<\/p>\n\n\n\n
x=\"hello\"\n\necho ${#x}<\/code><\/pre>\n\n\n\n![\"\"](\"http:\/\/fanaticboy.com\/wp-content\/uploads\/2022\/08\/image-1.png\")
<\/figure>\n\n\n\n\u4e8c\u3001\u83b7\u53d6\u5b50\u5b57\u7b26\u4e32<\/p>\n\n\n\n
x=\"qwertyuiop\"\n\necho ${x:1:4}#\u524d\u95ed\u540e\u5f00(]<\/code><\/pre>\n\n\n\n![\"\"](\"http:\/\/fanaticboy.com\/wp-content\/uploads\/2022\/08\/image-2.png\")
<\/figure>\n\n\n\n\u4e0a\u9762\u7684\u8868\u793a\u4ece\u7b2c\u4e8c\u4e2a\u5f00\u59cb\u83b7\u53d6\uff0c\u4e00\u5171\u56db\u4e2a\u5b57\u7b26<\/p>\n\n\n\n
\u4e09\u3001\u5355\u5f15\u53f7\u548c\u53cc\u5f15\u53f7<\/p>\n\n\n\n
\u4e00\u53e5\u8bdd\u603b\u7ed3\uff0c\u5355\u5f15\u53f7\u5185\u5bb9\u4e3a\u7eaf\u5b57\u7b26\u4e32\uff0c\u53cc\u5f15\u53f7\u91cc\u9762\u53ef\u4ee5\u53d6\u53d8\u91cf\u7684\u503c\uff0c\u4e3e\u4e2a\u4f8b\u5b50<\/p>\n\n\n\n
x=\"wode\"\ny=\"$x\"shijie\nz='$x'shijie\necho $y\necho $z<\/code><\/pre>\n\n\n\n![\"\"](\"http:\/\/fanaticboy.com\/wp-content\/uploads\/2022\/08\/image-3.png\")
<\/figure>\n\n\n\n\u56db\u3001\u5b57\u7b26\u4e32\u7684\u62fc\u63a5<\/p>\n\n\n\n
shell\u91cc\u9762\u7684\u5b57\u7b26\u4e32\u7684\u62fc\u63a5\u76f4\u63a5\u8f93\u51fa\u5230\u4e00\u5757\u5c31\u662f\u62fc\u63a5\u4e86\uff0c\u4e3e\u4e2a\u4f8b\u5b50<\/p>\n\n\n\n
x=\"wode\"\ny=\"shijie\"\nz=$x$y\necho $z\n\n<\/code><\/pre>\n\n\n\n![\"\"](\"http:\/\/fanaticboy.com\/wp-content\/uploads\/2022\/08\/image-4.png\")
<\/figure>\n\n\n\n\u4e94\u3001shell\u7684\u8fd0\u7b97\u7b26<\/p>\n\n\n\n
hell \u548c\u5176\u4ed6\u7f16\u7a0b\u8bed\u8a00\u4e00\u6837\uff0c\u652f\u6301\u591a\u79cd\u8fd0\u7b97\u7b26\uff0c\u5305\u62ec\uff1a<\/p>\n\n\n\n
- \u7b97\u6570\u8fd0\u7b97\u7b26<\/li>
- \u5173\u7cfb\uff08\u6bd4\u8f83\uff09\u8fd0\u7b97\u7b26<\/li>
- \u5e03\u5c14\u8fd0\u7b97\u7b26<\/li>
- \u5b57\u7b26\u4e32\u8fd0\u7b97\u7b26<\/li>
- \u6587\u4ef6\u6d4b\u8bd5\u8fd0\u7b97\u7b26<\/li><\/ul>\n\n\n\n
\uff08\u4e00\uff09\u4e0b\u8868\u5217\u51fa\u4e86\u5e38\u7528\u7684\u7b97\u672f\u8fd0\u7b97\u7b26\uff0c\u5177\u4f53\u7684\u5e94\u7528\u5728\u4e3e\u4f8b\u5217\u4e3e\u51fa\u6765\uff0c\u5047\u8bbex\u548cy\u90fd\u4e3a1\uff0c(())\u53ea\u652f\u6301\u6574\u6570<\/p>\n\n\n\n\u8fd0\u7b97\u7b26<\/th> \u8bf4\u660e<\/th> \u4e3e\u4f8b<\/th><\/tr> +<\/td> \u52a0\u6cd5<\/td> z=$(($x+$y)) echo $z<\/td><\/tr> –<\/td> \u51cf\u6cd5<\/td> z=$(($x-$y)) echo $z<\/td><\/tr> *<\/td> \u4e58\u6cd5<\/td> z=$(($x*$y)) echo $z<\/td><\/tr> \/<\/td> \u9664\u6cd5<\/td> z=$(($x\/$y)) echo $z<\/td><\/tr> %<\/td> \u53d6\u4f59<\/td> z=$(($x%$y)) echo $z<\/td><\/tr> =<\/td> \u8d4b\u503c<\/td> z=$x echo $z<\/td><\/tr> ==<\/td> \u76f8\u7b49\u3002\u7528\u4e8e\u6bd4\u8f83\u4e24\u4e2a\u6570\u5b57\uff0c\u76f8\u540c\u5219\u8fd4\u56de true\u3002<\/td> [ x==y ] \u8fd4\u56detrue<\/td><\/tr> !=<\/td> \u4e0d\u76f8\u7b49\u3002\u7528\u4e8e\u6bd4\u8f83\u4e24\u4e2a\u6570\u5b57\uff0c\u4e0d\u76f8\u540c\u5219\u8fd4\u56de true\u3002<\/td> [ x!=y ] \u8fd4\u56defalse<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n\uff08\u4e8c\uff09\u770b\u770b\u5173\u7cfb\u8fd0\u7b97\u7b26<\/p>\n\n\n\n
\u5173\u7cfb\u8fd0\u7b97\u7b26\u53ea\u652f\u6301\u6570\u5b57\uff0c\u4e0d\u652f\u6301\u5b57\u7b26\u4e32\uff0c\u9664\u975e\u5b57\u7b26\u4e32\u7684\u503c\u662f\u6570\u5b57\u3002<\/p>\n\n\n\n
\u4e0b\u8868\u5217\u51fa\u4e86\u5e38\u7528\u7684\u5173\u7cfb\u8fd0\u7b97\u7b26\uff0c\u5047\u5b9a\u53d8\u91cfx \u4e3a 1\uff0c\u53d8\u91cf y \u4e3a 1\uff1a<\/p>\n\n\n\n\u8fd0\u7b97\u7b26<\/th> \u8bf4\u660e<\/th> \u4e3e\u4f8b<\/th><\/tr> -eq<\/td> \u68c0\u6d4b\u4e24\u4e2a\u6570\u662f\u5426\u76f8\u7b49\uff0c\u76f8\u7b49\u8fd4\u56de true\u3002<\/td> [ x \u2212eq y ] \u8fd4\u56de true\u3002<\/td><\/tr> -ne<\/td> \u68c0\u6d4b\u4e24\u4e2a\u6570\u662f\u5426\u76f8\u7b49\uff0c\u4e0d\u76f8\u7b49\u8fd4\u56de true\u3002<\/td> [ x \u2212ne y ] \u8fd4\u56de false\u3002<\/td><\/tr> -gt<\/td> \u68c0\u6d4b\u5de6\u8fb9\u7684\u6570\u662f\u5426\u5927\u4e8e\u53f3\u8fb9\u7684\uff0c\u5982\u679c\u662f\uff0c\u5219\u8fd4\u56de true\u3002<\/td> [ x \u2212gt y ] \u8fd4\u56de false\u3002<\/td><\/tr> -lt<\/td> \u68c0\u6d4b\u5de6\u8fb9\u7684\u6570\u662f\u5426\u5c0f\u4e8e\u53f3\u8fb9\u7684\uff0c\u5982\u679c\u662f\uff0c\u5219\u8fd4\u56de true\u3002<\/td> [ x \u2212lt y ] \u8fd4\u56de false\u3002<\/td><\/tr> -ge<\/td> \u68c0\u6d4b\u5de6\u8fb9\u7684\u6570\u662f\u5426\u5927\u4e8e\u7b49\u4e8e\u53f3\u8fb9\u7684\uff0c\u5982\u679c\u662f\uff0c\u5219\u8fd4\u56de true\u3002<\/td> [ x \u2212ge y ] \u8fd4\u56de true\u3002<\/td><\/tr> -le<\/td> \u68c0\u6d4b\u5de6\u8fb9\u7684\u6570\u662f\u5426\u5c0f\u4e8e\u7b49\u4e8e\u53f3\u8fb9\u7684\uff0c\u5982\u679c\u662f\uff0c\u5219\u8fd4\u56de true\u3002<\/td> [ x \u2212le y ] \u8fd4\u56de true\u3002<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n \u90a3\u4e48\u8fd9\u91cc\u6709\u4e2a\u5c0f\u7684\u6280\u5de7\uff0c\u4e0d\u7528\u6b7b\u8bb0\u786c\u80cc\uff0c\u6bd4\u5982\u8bf4-eq\uff0ceq\u662fequal<\/p>\n\n\n\n
-ne –>not equal<\/p>\n\n\n\n
-gt –>greater than<\/p>\n\n\n\n
-lt –>less than<\/p>\n\n\n\n
-ge –>greater equal<\/p>\n\n\n\n
-le –>less equal<\/p>\n\n\n\n
\u628a\u4e0a\u9762\u7684\u5bf9\u5e94\u6210\u82f1\u6587\u662f\u4e0d\u662f\u5c31\u597d\u7406\u89e3\u4e86\u5462<\/p>\n\n\n\n
\uff08\u4e09\uff09\u5e03\u5c14\u8fd0\u7b97\u7b26<\/p>\n\n\n\n
\u4e0b\u8868\u5217\u51fa\u4e86\u5e38\u7528\u7684\u5e03\u5c14\u8fd0\u7b97\u7b26<\/p>\n\n\n\n\u8fd0\u7b97\u7b26<\/th> \u8bf4\u660e<\/th> \u4e3e\u4f8b<\/th><\/tr> !<\/td> \u975e\u8fd0\u7b97\uff0c\u8868\u8fbe\u5f0f\u4e3a true \u5219\u8fd4\u56de false\uff0c\u5426\u5219\u8fd4\u56de true\u3002<\/td> [ ! false ] \u8fd4\u56de true\u3002<\/td><\/tr> -o<\/td> \u6216\u8fd0\u7b97\uff0c\u6709\u4e00\u4e2a\u8868\u8fbe\u5f0f\u4e3a true \u5219\u8fd4\u56de true\u3002<\/td> [ 1 -eq 2 -o 1 -eq 1 ] \u8fd4\u56de true\u3002<\/td><\/tr> -a<\/td> \u4e0e\u8fd0\u7b97\uff0c\u4e24\u4e2a\u8868\u8fbe\u5f0f\u90fd\u4e3a true \u624d\u8fd4\u56de true\u3002<\/td> [ 1\u2212lt 1 \u2212a 1 \u2212lt 1 ] \u8fd4\u56de false\u3002<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n\uff08\u56db\uff09\u903b\u8f91\u8fd0\u7b97\u7b26<\/p>\n\n\n\n\u8fd0\u7b97\u7b26<\/th> \u8bf4\u660e<\/th> \u4e3e\u4f8b<\/th><\/tr> &&<\/td> \u903b\u8f91\u7684 AND<\/td> [[ 1 -lt 1 && 1 -gt 0 ]] \u8fd4\u56de false<\/td><\/tr> ||<\/td> \u903b\u8f91\u7684 OR<\/td> [[ 2 -lt 3 || 1 -gt 2 ]] \u8fd4\u56de true<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n\u5728\u903b\u8f91\u8fd0\u7b97\u7b26\u4e2d\uff0c\u8868\u8fbe\u5f0f\u9700\u8981\u7528[[]],\u800c\u5e03\u5c14\u8868\u8fbe\u5f0f\u662f[]\u5c31\u53ef\u4ee5\u4e86\uff0c\u4e0d\u80fd\u7528\u9519\u3002\u8fd9\u4e9b\u7528\u5230\u7684\u5730\u65b9\u5c31\u662f\u5728\u6761\u4ef6\u5224\u65ad\u7684\u65f6\u5019\u4e86\u3002\u800c\u63a5\u4e0b\u6765\u7684\u5185\u5bb9\u5c31\u8981\u8be6\u7ec6\u4ecb\u7ecd\u6761\u4ef6\u5224\u65ad\u6a21\u5757<\/p>\n\n\n\n
\uff08\u4e94\uff09\u5b57\u7b26\u4e32\u8fd0\u7b97\u7b26<\/p>\n\n\n\n\u8fd0\u7b97\u7b26<\/th> \u8bf4\u660e<\/th> \u4e3e\u4f8b<\/th><\/tr> =<\/td> \u68c0\u6d4b\u4e24\u4e2a\u5b57\u7b26\u4e32\u662f\u5426\u76f8\u7b49\uff0c\u76f8\u7b49\u8fd4\u56de true\u3002<\/td> [ “a” = “b” ] \u8fd4\u56de false\u3002<\/td><\/tr> !=<\/td> \u68c0\u6d4b\u4e24\u4e2a\u5b57\u7b26\u4e32\u662f\u5426\u4e0d\u76f8\u7b49\uff0c\u4e0d\u76f8\u7b49\u8fd4\u56de true\u3002<\/td> [ “a” != “b” ] \u8fd4\u56de true\u3002<\/td><\/tr> -z<\/td> \u68c0\u6d4b\u5b57\u7b26\u4e32\u957f\u5ea6\u662f\u5426\u4e3a0\uff0c\u4e3a0\u8fd4\u56de true\u3002<\/td> [ -z “a” ] \u8fd4\u56de false\u3002<\/td><\/tr> -n<\/td> \u68c0\u6d4b\u5b57\u7b26\u4e32\u957f\u5ea6\u662f\u5426\u4e0d\u4e3a 0\uff0c\u4e0d\u4e3a 0 \u8fd4\u56de true\u3002<\/td> [ -n “a” ] \u8fd4\u56de true\u3002<\/td><\/tr> $<\/td> \u68c0\u6d4b\u5b57\u7b26\u4e32\u662f\u5426\u4e0d\u4e3a\u7a7a\uff0c\u4e0d\u4e3a\u7a7a\u8fd4\u56de true\u3002<\/td> [ $”a” ] \u8fd4\u56de true\u3002<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n\u516d\u3001\u7b80\u5355\u7684\u6761\u4ef6\u5224\u65ad<\/p>\n\n\n\n
\u8fd9\u91cc\u7b80\u5355\u8bf4\u4e00\u4e0b\uff0c\u4e3a\u4e0b\u9762\u94fa\u57ab\u4e00\u4e0b\u3002\u5176\u4e2d\u683c\u5f0f\u4e3a\uff1a<\/p>\n\n\n\n
\nif [ \u8868\u8fbe\u5f0f ]\nthen\n\u8bed\u53e5\nfi<\/code><\/pre>\n\n\n\n\u9996\u5148\u521b\u5efatest3.sh\u6587\u4ef6<\/p>\n\n\n\n
\u5728\u91cc\u9762\u5199\u4e0a\u5185\u5bb9<\/p>\n\n\n\n
if [ 1 -eq 1 ]\nthen\necho \"hello world\"\nfi\n\n<\/code><\/pre>\n\n\n\n\u8ba9\u6211\u4eec\u6267\u884c\u4e00\u4e0b<\/p>\n\n\n\n![\"\"](\"http:\/\/fanaticboy.com\/wp-content\/uploads\/2022\/08\/image-5.png\")
<\/figure>\n\n\n\n\u4e00\u4e9b\u7b54\u7591<\/p>\n\n\n\n
\u95ee\uff1a\u53ea\u8bfb\u53d8\u91cf\u53ef\u4ee5\u88ab\u5220\u9664\u5417<\/p>\n\n\n\n
\u7b54\uff1a\u4e0d\u53ef\u4ee5\uff0c\u53ea\u8bfb\u53d8\u91cf\u4e0d\u4f1a\u88ab\u5220\u9664<\/p>\n\n\n\n
\u95ee\uff1a\u5728\u505a\u7b97\u6570\u8fd0\u7b97\u7684\u65f6\u5019\u5fc5\u987b\u662f(())\u5417<\/p>\n\n\n\n
\u7b54\uff1a\u4e0d\u662f\u7684\uff0c\u8fd9\u53ea\u662f\u6574\u6570\u8fd0\u7b97\u7684\u4e00\u79cd\uff0c\u8fd8\u53ef\u4ee5\u7528\u5176\u4ed6\u7684\u6bd4\u5982let<\/p>\n\n\n\n
let a=1+2\necho $a\n<\/code><\/pre>\n\n\n\n\u5982\u679c\u662f\u5c0f\u6570\u7684\u8bdd\u7528bc\uff0c\u6bd4\u5982<\/p>\n\n\n\n
echo 1+2 | bc\n<\/code><\/pre>\n\n\n\n\u95ee\uff1a-a\u548c&&\u4e0e-o\u548c||\u6709\u4ec0\u4e48\u533a\u522b\u5462<\/p>\n\n\n\n
\u7b54\uff1a\u5176\u5b9e\u610f\u601d\u662f\u4e00\u6837\u7684\uff0c\u4f46-a\u548c&&\u533a\u522b\u662f-a\u4e24\u8fb9\u90fd\u6267\u884c\uff0c\u7136\u540e\u5224\u65ad\u3002&&\u662f\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u6267\u884c\uff0c\u6210\u529f\u5f80\u4e0b\u6267\u884c\uff0c\u5931\u8d25\u7ec8\u6b62\u6267\u884c\u3002-o\u548c||\u7684\u8bdd\u4e5f\u662f-o\u4e24\u8fb9\u540c\u65f6\u6267\u884c\uff0c||\u7684\u8bdd\u5de6\u8fb9\u4e0d\u6210\u529f\u7ee7\u7eed\u5f80\u4e0b\u6267\u884c\uff0c\u6210\u529f\u5c31\u4e0d\u5f80\u4e0b\u6267\u884c\u4e86<\/p>\n\n\n\n
\u4ee5\u4e0a\u5c31\u662f\u5173\u4e8eshell\u811a\u672c\u7684\u672c\u7bc7\u6587\u7ae0\u7684\u5185\u5bb9\u4e86\uff0c\u63a5\u4e0b\u6765\u4f1a\u6301\u7eed\u66f4\u65b0~ \u200b<\/p>\n","protected":false},"excerpt":{"rendered":"
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