文件描符??????縮寫??????????????????描述

0????????????????????STDIN??????????標準輸入
1????????????????????STDOUT??????標準輸出
2????????????????????STDERR??????標準錯誤

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1、重定向錯誤和數據

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[root@logicserver?tmp]#?ls?-al?data1?haha?2>?qingyun.txt?1>pangfeng.txt [root@logicserver?tmp]#?cat?qingyun;cat?pangfeng.txt? cat:?qingyun:?沒有那個文件或目錄 -rw-r--r--.?1?root?root?269?9月??18?09:54?data1

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2、在腳本重定向輸出

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2.1臨時重定向

故意在腳本生成錯誤消息，可以將單獨的一行輸出重定向到STDERR,在文件描述符數字前加一個and符(&)

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[root@logicserver?tmp]#?vim?data6 #!/bin/bash # echo?"This?is?an?error"?>&2 echo?"This?is?a?normal?output"

運行腳本，看不出本質區別

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?[root@logicserver?tmp]#?sh?data6 This?is?an?error This?is?a?normal?output

默認情瓿上，Linux將STDERR定向到STDOUT，但在運行腳本時重定向了STDERR，腳本中所有定向到STDERRR的文本都會被重定向

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[root@logicserver?tmp]#?sh?data6?2>?data7 This?is?a?normal?output [root@logicserver?tmp]#?cat?data7 This?is?an?error

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2.2永久重定向

如果腳本有大量數據需要重定定，那重定向每個echo語名會很煩瑣。用exec命令告訴 shell腳本執行期間重定向某個特定文件描述符

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?[root@logicserver?tmp]#?vim?data7 #!/bin/bash # exec?1>?testout echo?"This?is?a?test?of?redirecting?all?output" echo?"from?a?scirpt?to?another?file" echo?"without?having?to?redirect?every?individual?line"

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[root@logicserver?tmp]#?sh?data7 [root@logicserver?tmp]#?ll?test test?????testout??test.sh?? [root@logicserver?tmp]#?cat?testout? This?is?a?test?of?redirecting?all?output from?a?scirpt?to?another?file

exec命令訓動一個新shell并將STDOUT文件描述符重定向到文件

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[root@logicserver?tmp]#?vim?data7 #!/bin/bash # exec?2>?testerror echo?"this?is?a?error" exec?1>?testout echo?"This?is?a?test?of?redirecting?all?output" echo?"from?a?scirpt?to?another?file" echo?"Wrong?a?time"?>&2

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3、 重定向輸入

exec命令允許將STDINT重定向到Linux系統上文件
exec 0< testfile

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[root@logicserver?tmp]#?cat?data1 the?quick?brown?fox?jumps?over?the?lazy?dog1 the?quick?brown?fox?jumps?over?the?lazy?dog2 the?quick?brown?fox?jumps?over?the?lazy?dog3 the?quick?brown?fox?jumps?over?the?lazy?dog4 the?quick?brown?fox?jumps?over?the?lazy?dog5 the?quick?brown?fox?jumps?over?the?lazy?dog6 [root@logicserver?tmp]#?vim?data8 #!/bin/bash # exec?0<?data1 read?LINE count=1 while?[?$??-eq?0?] do ????????echo?"Line#$count:$LINE" ????????count=$[?$count+1?] ????????read?LINE done

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?[root@logicserver?tmp]#?sh?data8 Line#1:the?quick?brown?fox?jumps?over?the?lazy?dog1 Line#2:the?quick?brown?fox?jumps?over?the?lazy?dog2 Line#3:the?quick?brown?fox?jumps?over?the?lazy?dog3 Line#4:the?quick?brown?fox?jumps?over?the?lazy?dog4 Line#5:the?quick?brown?fox?jumps?over?the?lazy?dog5 Line#6:the?quick?brown?fox?jumps?over?the?lazy?dog6

也可以這樣寫

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?[root@logicserver?tmp]#?vim?data8 #!/bin/bash # exec?0<?data1 count=1 while?read?LINE do ????????echo?"Line#$count:$LINE" ????????count=$[?$count+1?] done

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本文轉自 zouqingyun 51CTO博客，原文鏈接：http://blog.51cto.com/zouqingyun/1697088，如需轉載請自行聯系原作者

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