{"id":1334,"date":"2014-09-29T15:35:55","date_gmt":"2014-09-29T15:35:55","guid":{"rendered":"http:\/\/ixyzero.com\/blog\/?p=1334"},"modified":"2014-09-29T15:35:55","modified_gmt":"2014-09-29T15:35:55","slug":"bash%e4%b8%ad%e7%9a%84%e7%a9%ba%e6%a0%bc","status":"publish","type":"post","link":"https:\/\/ixyzero.com\/blog\/archives\/1334.html","title":{"rendered":"Bash\u4e2d\u7684\u7a7a\u683c"},"content":{"rendered":"

\u5b9e\u5728\u65e0\u804a\uff0c\u6ca1\u4ec0\u4e48\u76ee\u7684\u6027\uff0c\u5c31\u968f\u610f\u641c\u7d22\/\u7ffb\u770b\u4e4b\u524d\u7684\u7b14\u8bb0\uff0c\u8bd5\u56fe\u627e\u4e9b\u65b0\u9c9c\u7684\u4e1c\u897f\u4e86\u89e3\uff0c\u770b\u5230\u4e86\u7bc7\u4e4b\u524d\u6536\u85cf\u7684\u6587\u7ae0\uff1aBash\u7a7a\u683c\u7684\u90a3\u70b9\u4e8b<\/a>\uff0c\u5199\u5f97\u4e0d\u9519\uff0c\u7ecf\u5e38\u5728Bash\u811a\u672c\u4e2d\u4f1a\u78b0\u5230\uff0c\u4f46\u4e5f\u6ca1\u6709\u4e2a\u7cfb\u7edf\u6027\u7684\u603b\u7ed3\uff0c\u90a3\u73b0\u5728\u5c31\u5148\u5c31\u8fd9\u4ed6\u7684\u8fd9\u7bc7\u6587\u7ae0\uff0c\u6211\u4e5f\u597d\u597d\u56de\u987e\u4e00\u4e0b\u5427\uff08\u5927\u4f53\u7ed3\u6784\u548c\u5185\u5bb9\u7167\u642c\u539f\u6587\uff0c\u81ea\u5df1\u8fdb\u884c\u5b9e\u8df5\u9a8c\u8bc1\uff09\uff1a<\/p>\n

\u7a7a\u683c\uff0c\u4e00\u4e2a\u770b\u4e0d\u89c1\u7684\u5b57\u7b26\uff0c\u5f88\u4e0d\u8d77\u773c\uff0c\u4e5f\u6b63\u7531\u4e8e\u4e0d\u8d77\u773c\uff0c\u5f88\u591a\u4eba\u7ecf\u5e38\u5ffd\u7565\u5b83\uff0c\u5bfc\u81f4\u4ee3\u7801\u51fa\u9519\uff0c\u5374\u8fd8\u627e\u4e0d\u7740\u5317\u3002\u8fd9\u91cc\uff0c\u6211\u4eec\u6765\u804a\u804abash\u4e2d\u7a7a\u683c\u7684\u90a3\u70b9\u4e8b\u3002<\/p>\n

\u5148\u4e86\u89e3\u4e0bbash\u4e2d\u4ec0\u4e48\u65f6\u5019\u8be5\u7528\u7a7a\u683c\uff0c\u4ec0\u4e48\u65f6\u5019\u4e0d\u8be5\u7528\uff1a<\/p>\n

\n

1. \u7b49\u53f7\u8d4b\u503c\u4e24\u8fb9\u4e0d\u80fd\u6709\u7a7a\u683c<\/strong><\/span>
\n2. \u547d\u4ee4\u4e0e\u9009\u9879\u4e4b\u95f4\u9700\u8981\u7a7a\u683c
\n3. \u7ba1\u9053\u4e24\u8fb9\u7a7a\u683c\u53ef\u6709\u53ef\u65e0<\/p>\n<\/blockquote>\n

\u4e0b\u9762\u6211\u4eec\u6765\u770b\u770b\u5e38\u89c1\u7684\u95ee\u9898\uff1a<\/p>\n

1. \u8d4b\u503c\u65f6\u7b49\u53f7\u4e24\u8fb9\u6216\u8005\u53ea\u6709\u5de6\u8fb9\u591a\u4e86\u7a7a\u683c<\/p>\n

hi@linux ~ $ var1 = test\nbash: var1: command not found\nhi@linux ~ $ echo ${var1:?error}\nbash: var1: error\nhi@linux ~ $ echo ${var1?error}\nbash: var1: error\n\nhi@linux ~ $ var2 =test\nNo command 'var2' found, did you mean:\n Command 'par2' from package 'par2' (universe)\nvar2: command not found\nhi@linux ~ $ echo ${var2:?error}\nbash: var2: error\nhi@linux ~ $ echo ${var2?error}\nbash: var2: error<\/pre>\n
\u8fd9\u91cc\u6211\u7528\u4e86bash\u7684\u53d8\u91cf\u6269\u5c55\uff0c${var1:?error}\u5f53var1\u4e3aunset\u6216null(\u672a\u5b9a\u4e49\u6216\u7a7a)\u65f6, \u62a5\u6307\u5b9a\u9519\u8bef\uff1b${var1?error}\u5f53var1\u4e3aunset\u65f6\uff0c\u62a5\u6307\u5b9a\u9519\u8bef\u3002\u4ece\u6267\u884c\u7ed3\u679c\u6765\u770b\uff0c\u5982\u679c\u7b49\u53f7\u5de6\u8fb9\u6709\u7a7a\u683c\uff0c\u5219\u53d8\u91cf\u540d\u5f53\u6210\u547d\u4ee4\u6267\u884c\uff0c\u7ed3\u679c\u62a5command not found\uff0c\u53d8\u91cf\u6ca1\u6709\u88ab\u8d4b\u503c\u3002<\/p>\n
\u8d4b\u503c\u65f6\u7b49\u53f7\u5de6\u8fb9\u6ca1\u6709\u7a7a\u683c\uff0c\u53f3\u8fb9\u6709\u7a7a\u683c(\u8fd9\u79cd\u60c5\u51b5\u6709\u70b9\u7279\u522b\uff0c\u4f60\u4f1a\u53d1\u73b0\u4e24\u79cd\u60c5\u51b5)<\/span>\uff1a<\/p>\n
hi@linux ~ $ var= test\nhi@linux ~ $ var= nocmd\nbash: nocmd: command not found<\/pre>\n
\u540c\u6837\u662f\u7b49\u53f7\u53f3\u8fb9\u6709\u7a7a\u683c\uff0c\u7b2c\u4e00\u6761\u547d\u4ee4\u6ca1\u62a5\u9519\uff0c\u800c\u7b2c\u4e8c\u6761\u62a5\u9519\u4e86\u3002
\n\u8fd9\u662f\u56e0\u4e3ashell\u4e2d\u6709\u8fd9\u4e48\u4e00\u79cd\u6267\u884c\u547d\u4ee4\u7684\u65b9\u5f0f: var=string command\u00a0<\/span><\/strong>\u547d\u4ee4command\u5c06\u5f97\u5230\u53d8\u91cfvar\u7684\u503c<\/span><\/strong>(\u81f3\u4e8e\u5728\u547d\u4ee4\u6267\u884c\u540e\uff0c\u53d8\u91cfvar\u7684\u503c\u662f\u5426\u4fdd\u7559\u4e0b\u6765\uff0cbash4\u4e2d\u6ca1\u6709\u4fdd\u7559\uff0c\u4f46\u6211\u5728dash\u4e2d\u53d1\u73b0\u65f6\u4fdd\u7559\u4e0b\u6765\u7684\uff0c\u4e0d\u540c\u7684shell\u5bf9\u8fd9\u4e2a\u7684\u5904\u7406\u4e0d\u540c), \u7531\u4e8etest\u662f\u4e2a\u547d\u4ee4\uff0c\u800cnocmd\u4e0d\u662f\uff0c\u6240\u4ee5\u62a5\u4e86command not found.\u7684\u9519\u8bef\u3002<\/p>\n
hi@linux ~ $ var=newtest eval echo $var\nnewtest\nhi@linux ~ $ echo $var<\/pre>\n
\u6ce8\u610f: \u8fd9\u91cc\u6211\u4f7f\u7528\u4e86eval, \u662f\u60f3\u907f\u514d\u5728\u7b2c\u4e00\u6b21\u89e3\u6790\u65f6$var\u88ab\u66ff\u6362\u6210\u7a7a\u5b57\u7b26\u4e32, \u4e0d\u7136\u5c31\u4f1a\u51fa\u73b0\u4e0b\u9762\u7684\u60c5\u51b5(\u4e0b\u9762\u662f\u9519\u8bef\u7684\u6d4b\u8bd5\u65b9\u6cd5\uff0c\u5728echo\u8fd8\u6ca1\u6267\u884c\u65f6\uff0c$var\u5df2\u7ecf\u88ab\u66ff\u6362\u6210\u7a7a\u5b57\u7b26\u4e32)\uff1a<\/p>\n
hi@linux ~ $ var=newtest echo $var\n\nhi@linux ~ $ echo $var<\/pre>\n
\u5230\u8fd9\u91cc\uff0c\u76f8\u4fe1\u5927\u5bb6\u90fd\u660e\u767d\u4e86\u5427\uff0c\u5bf9\u4e8e\u7b49\u53f7\u8d4b\u503c\uff0c\u5de6\u53f3\u4e24\u8fb9\u4e0d\u53ef\u4ee5\u6709\u7a7a\u683c\uff0c\u867d\u7136\u53f3\u8fb9\u6709\u7a7a\u683c\u4e0d\u4e00\u5b9a\u62a5\u9519\uff0c\u4f46\u90a3\u7edd\u5bf9\u4e0d\u662f\u4f60\u60f3\u8981\u7684\u7ed3\u679c\u3002<\/strong><\/span>
\n\u547d\u4ee4\u548c\u9009\u9879\u4e4b\u95f4\u5fc5\u987b\u6709\u7a7a\u683c \u8fd9\u4e2a\u4f3c\u4e4e\u5927\u5bb6\u90fd\u660e\u767d\uff0c\u4e3a\u4f55\u6211\u8fd8\u8fd9\u4e48\u7f57\u55e6\u5462\uff1f\u8bf4\u5230\u8fd9\u91cc\uff0c\u4e0d\u5f97\u4e0d\u63d0\u4e00\u4e0b\u4e00\u4e2a\u975e\u5e38\u7279\u522b\u7684\u547d\u4ee4: [ \u547d\u4ee4(\u4f60\u6ca1\u770b\u9519\uff0c\u662f[ ), \u4e5f\u5c31\u662ftest\u547d\u4ee4(\u5728bash\u4e2d\uff0c\u8fd9\u662f\u4e2a\u5185\u7f6e\u547d\u4ee4\uff0c\u4f46\u5728\u8fd9\u91cc\u4e0d\u5f71\u54cd\u6211\u4eec\u7684\u7406\u89e3)\u3002\u6216\u8bb8\u4f60\u4f1a\u89c9\u5f97[\u547d\u4ee4\u773c\u719f\uff0c\u6ca1\u9519\uff0c\u6211\u4fdd\u8bc1\u4f60\u89c1\u8fc7\u5b83\uff0c\u6765\u770b\u770b\u4e0b\u9762\u7684\u4f8b\u5b50<\/p>\n
hi@linux ~ $ if [ 'abc' = 'abc' ]; then echo 'they are the same'; fi\nthey are the same\nhi@linux ~ $ type -a [\n[ is a shell builtin\n[ is \/usr\/bin\/[<\/pre>\n
\u60f3\u8d77\u6765\u4e86\u5427\uff1f[\u547d\u4ee4\u7ecf\u5e38\u7528\u5230if\u5224\u65ad\u4e2d\uff0c\u5f53\u7136\u4e5f\u6709\u4eba\u559c\u6b22\u8fd9\u4e48\u5199\uff1a<\/p>\n
hi@linux ~ $ [ 'abc' = 'cba' ] || echo 'they are not the same'\nthey are not the same\nhi@linux ~ $ type -a [\n[ is a shell builtin\n[ is \/usr\/bin\/[<\/pre>\n
[ \u547d\u4ee4\u6b63\u540d\u53ebtest\u547d\u4ee4\uff0c\u5b83\u4eec\u4e24\u8005\u51e0\u4e4e\u4e00\u6837\uff0c\u4e3a\u4ec0\u4e48\u4e0d\u662f\u5b8c\u5168\u4e00\u6837\uff1f\u6765\u770b\u770b\u8fd9\u4e2a\uff1a<\/p>\n
hi@linux ~ $ [ 'abc' = 'cba'\nbash: [: missing `]'\nhi@linux ~ $ [ 'abc' = 'cba' ]\nhi@linux ~ $ test 'abc' = 'cba' ]\nbash: test: too many arguments\nhi@linux ~ $ test 'abc' = 'cba'<\/pre>\n
\u6e05\u6670\u4e86\u5427\uff0c\u7528[\u547d\u4ee4\u65f6\uff0c\u4f60\u5fc5\u987b\u7ed9\u5b83\u4e2a\u5c3e\u5df4], \u7528test\u547d\u4ee4\u65f6\uff0c\u5c31\u4e0d\u80fd\u52a0\u4e2a\u5c3e\u5df4\u3002\u5c3e\u5df4\uff3d\u662f[\u6700\u540e\u4e00\u4e2a\u53c2\u6570\uff0c\u4e0d\u53ef\u7f3a\u5c11\u7684\u53c2\u6570, \u4ee3\u8868[\u547d\u4ee4\u7684\u7ed3\u675f\u3002<\/p>\n
\u626f\u4e86\u8fd9\u4e48\u591a\uff0c\u90a3\u5230\u5e95\u8fd9\u4e2a\u548c\u7a7a\u683c\u6709\u6bdb\u5173\u7cfb\uff1f\u8bf4\u8fd9\u4e9b\uff0c\u662f\u5148\u8ba9\u5927\u5bb6\u660e\u767d\uff1a[\u5728shell\u4e2d\u662f\u4e2a\u547d\u4ee4\uff0c\u5b83\u5de6\u53f3\u5fc5\u987b\u6709\u7a7a\u683c\uff01]\u662f[\u7684\u6700\u540e\u4e0d\u53ef\u7f3a\u5c11\u7684\u53c2\u6570\uff0c\u5b83\u4e24\u8fb9\u4e5f\u9700\u8981\u7a7a\u683c(\u867d\u7136\u6709\u4e9b\u547d\u4ee4\u7684\u53c2\u6570\u80fd\u8fde\u4e00\u8d77\uff0c\u4f8b\u5982ps, \u4f46\uff3b\u547d\u4ee4\u4e0d\u884c\uff0c\u5b83\u7684\u53c2\u6570\u4e4b\u95f4\u5fc5\u987b\u6709\u7a7a\u683c)<\/strong><\/span>\u3002\u8ba9\u6211\u4eec\u770b\u770b\u5173\u4e8e[\u5e38\u89c1\u7684\u9519\u8bef\uff1a<\/p>\n
a. if \u4e0e [ \u4e4b\u95f4\u7f3a\u5c11\u7a7a\u683c<\/h6>\n
hi@linux ~ $ if[ '$HOME' = '\/home\/hi'];then echo 'equal'; fi\nbash: syntax error near unexpected token `then'\nhi@linux ~ $ if[ '$HOME' = '\/home\/hi' ];then echo 'equal'; fi\nbash: syntax error near unexpected token `then'\nhi@linux ~ $ if['$HOME' = '\/home\/hi'];then echo 'equal'; fi\nbash: syntax error near unexpected token `then'\nhi@linux ~ $ if['$HOME' = '\/home\/hi' ];then echo 'equal'; fi\nbash: syntax error near unexpected token `then'<\/pre>\n
\u8bed\u6cd5\u5206\u6790\u9519\u8bef\uff0c\u5f88\u660e\u663e\uff0cif[ \u5bf9\u4e8ebash\u6765\u8bf4\uff0c\u4e0d\u77e5\u9053\u662f\u4ec0\u4e48\u9b3c\u4e1c\u897f\u3002<\/p>\n
b. [\u4e0e\u540e\u9762\u7684\u53c2\u6570\u4e4b\u95f4\u7f3a\u5c11\u7a7a\u683c<\/h6>\n
hi@linux ~ $ if ['$HOME' = '\/home\/hi' ];then echo 'equal'; fi\nbash: [\/home\/hi: No such file or directory\nhi@linux ~ $ if ['$HOME' = '\/home\/hi'];then echo 'equal'; fi\nbash: [\/home\/hi: No such file or directory<\/pre>\n
[“$HOME” \u5bf9\u4e8ebash\u6765\u8bf4\uff0c\u4e5f\u4e0d\u77e5\u9053\u662f\u4ec0\u4e48\u9b3c\u4e1c\u897f\u3002<\/p>\n
c. [ ] \u4e4b\u95f4\u7684\u53c2\u6570\u4e4b\u95f4\u7f3a\u5c11\u7a7a\u683c<\/h6>\n
hi@linux ~ $ if [ 'abc'='abc' ]; then echo 'equal'; fi\nequal\nhi@linux ~ $ if [ 'abc'='cba' ]; then echo 'equal'; fi\nequal<\/pre>\n
\u7b2c\u4e00\u6761\u547d\u4ee4\u4f3c\u4e4e\u662f\u5bf9\u7684(\u5b9e\u9645\u4e0a\u662f\u6b63\u5de7\u800c\u5df2)\uff0c\u770b\u770b\u7b2c\u4e8c\u6761\u547d\u4ee4”abc” \u548c “cba”\u660e\u663e\u4e0d\u540c\uff0c\u4f46\u5374\u5224\u65ad\u4e3a\u76f8\u540c\u3002\u8fd9\u662f\u56e0\u4e3a\u53c2\u6570\u4e4b\u95f4\u7f3a\u5c11\u4e86\u7a7a\u683c\uff0c\u88ab[\u547d\u4ee4\u8ba4\u4e3a\u5185\u90e8\u662f\u4e2a\u503c\u800c\u5df2\u3002\u770b\u770b\u4e0b\u9762\u7684\u547d\u4ee4\uff0c\u4f60\u5c31\u4f1a\u91ca\u7136\u4e86\uff1a<\/p>\n
hi@linux ~ $ if [ 0 ]; then echo 'equal'; fi\nequal\nhi@linux ~ $ if [ '1' ]; then echo 'equal'; fi\nequal\nhi@linux ~ $ if [ '' ]; then echo 'equal'; fi\nhi@linux ~ $ if [ ]; then echo 'equal'; fi<\/pre>\n
\u5728[ ] \u5185\u90e8\uff0c\u5982\u679c\u53ea\u6709\u4e00\u4e2a\u503c(\u90a3\u4e9b\u56e0\u4e3a\u7f3a\u5c11\u4e86\u7a7a\u683c\u800c\u8fde\u4e00\u8d77\u7684\u4e5f\u7b97)\uff0c\u4e0d\u662f\u7a7a\u5b57\u7b26\u4e32\u5c31\u4e3a\u771f\u3002\u6240\u4ee5\u5728[ ] \u4e4b\u95f4\u7684\u53c2\u6570\uff0c\u4e5f\u8981\u4e24\u8fb9\u6709\u7a7a\u683c\uff0c\u800c\u4e0d\u80fd\u5806\u4e00\u8d77<\/span>\u3002<\/p>\n
d. \u53c2\u6570\u548c\u5c3e\u5df4]\u4e4b\u95f4\u7f3a\u5c11\u7a7a\u683c<\/h6>\n
\u8fd9\u4e2a\u5c31\u4e0d\u7f57\u55e6\u4e86\uff0c\u5c3e\u5df4]\u4e5f\u662f[\u547d\u4ee4\u7684\u53c2\u6570\uff0c\u5982\u540c\u4e0a\u9762\u6240\u8bb2\uff0c\u53c2\u6570\u4e4b\u95f4\u5fc5\u987b\u6709\u7a7a\u683c
\n\u626f\u4e86\u8fd9\u4e48\u591a[\u547d\u4ee4\u4e0e\u7a7a\u683c\u7684\u4e8b\uff0c\u4f46\u6709\u4e9b\u65f6\u5019\uff0c\u7f3a\u4e86\u7a7a\u683c\u5374\u80fd\u6b63\u786e\u8fd0\u884c, \u5f53\u7136\u8fd9\u53ea\u662f\u4f60\u597d\u8fd0, \u4e00\u8d77\u6765\u770b\u770b\uff1a<\/p>\n
hi@linux ~ $ var=' abc'\nhi@linux ~ $ if [$var = 'abc' ];then echo 'equal'; fi\nequal\nhi@linux ~ $ if ['$var' = 'abc' ];then echo 'equal'; fi\nbash: [ abc: command not found<\/pre>\n
\u4e4b\u524dBash\u5f15\u53f7\u90a3\u70b9\u4e8b\u63d0\u5230\u8fc7\uff0c\u53cc\u5f15\u53f7\u5305\u56f4\u8d77\u6765\u7684\u662f\u4e00\u4e2a\u6574\u4f53\uff0c\u800c\u6ca1\u53cc\u5f15\u53f7\u7684\u65f6\u5019\uff0c\u5b57\u7b26\u4e32\u524d\u540e\u7684\u7a7a\u683c\u6216\u5236\u8868\u7b26\u90fd\u88ab\u5207\u5f00\u3002\u5982\u679c\u6070\u5de7\u4f60\u9047\u5230\u4e86\u6216\u8005\u4f60\u6545\u610f\u8981\u4e22\u5f03\u5b57\u7b26\u4e32\u524d\u540e\u7684\u7a7a\u683c\u6216\u5236\u8868\u7b26\uff0c\u90a3\u4e5f\u4e0d\u662f\u4e0d\u53ef\u80fd, \u4f46\u975e\u5e38\u4e0d\u5efa\u8bae\u4f60\u8fd9\u4e48\u5199\uff0c\u4f60\u7684\u4ee3\u7801\u5c06\u662f\u975e\u5e38\u8106\u5f31\u7684\u3002<\/p>\n
\u6216\u8005\u4f60\u8be5\u52a0\u7684\u7a7a\u683c\u90fd\u52a0\u4e86\uff0c\u4f46\u8fd8\u662f\u62a5\u9519\uff0c\u8fd9\u4e5f\u53ef\u80fd\u548c\u7f3a\u5c11\u53cc\u5f15\u53f7\u6709\u5173\u3002<\/span>\u8fd9\u6837\u7684\u60c5\u51b5\u5f88\u666e\u904d\uff0c\u6700\u540e\u518d\u770b\u770b\uff1a<\/p>\n
hi@linux ~ $ var=''\nhi@linux ~ $ if [ '$var' = 'abc' ];then echo 'equal'; fi\nhi@linux ~ $ if [ $var = 'abc' ];then echo 'equal'; fi\nbash: [: =: unary operator expected\nhi@linux ~ $ dvar='a b c'\nhi@linux ~ $ if [ $dvar = 'a b c' ];then echo 'equal'; fi\nbash: [: too many arguments\nhi@linux ~ $ if [ '$dvar' = 'a b c' ];then echo 'equal'; fi\nequal<\/pre>\n
\u6211\u518d\u7f57\u55e6\u4e00\u6b21\uff0c\u4e0d\u8981\u8f7b\u6613\u7701\u7565\u53cc\u5f15\u53f7\u3002\u5f88\u6e05\u695a\u4e86\u5427\uff1f\u5982\u679c\u4f60\u8fd8\u4e0d\u660e\u767d\uff0c\u8bf7\u8bfb\u8bfb\uff1aBash\u5f15\u53f7\u90a3\u70b9\u4e8b<\/a>\u3002<\/p>\n
\u6700\u540e\uff0c\u5bf9\u4e8e\u7ba1\u9053\u4e24\u8fb9\u53ef\u6709\u53ef\u65e0\u7684\u7a7a\u683c\uff0c\u5c31\u4e0d\u626f\u6de1\u4e86\uff0c\u56e0\u4e3a\u6ca1\u9047\u5230\u6709\u4eba\u5bf9\u6b64\u6709\u7591\u60d1\u3002<\/p>\n
 <\/p>\n
\u53c2\u8003\/\u62d3\u5c55\u94fe\u63a5\uff1a<\/h6>\n