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Hash: SHA512 |
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On 03/23/2013 01:44 PM, Alec Warner wrote: |
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> On Sat, Mar 23, 2013 at 9:26 AM, Michał Górny <mgorny@g.o> |
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> wrote: |
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>> + # Close the lock file when we are done |
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>> with it. + # Prevents deadlock if we aren't |
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>> in a subshell. + eval "exec ${lock_fd}>&-" |
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> |
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> Not following this bit. |
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> |
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> The bash manpage says N>&DIGIT- redirects fd DIGIT to fd N. N may |
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> be unspecified and defaults to 1. |
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> |
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> It doesn't say what happens if DIGIT is unspecified. Nor does it |
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> say it closes any file descriptors. |
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> |
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|
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The relevant section of bash(1) is reproduced below: |
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|
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Duplicating File Descriptors |
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The redirection operator |
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|
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[n]<&word |
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|
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is used to duplicate input file descriptors. If word expands to |
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one or more digits, the file descriptor denoted by n is made to |
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be a copy of that file descriptor. If the digits in word do not |
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specify a file descriptor open for input, a redirection error |
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occurs. If word evaluates to -, file descriptor n is closed. |
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If n is not specified, the standard input (file descriptor 0) is |
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used. |
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|
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The operator |
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|
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[n]>&word |
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|
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is used similarly to duplicate output file descriptors. If n is |
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not specified, the standard output (file descriptor 1) is used. |
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If the digits in word do not specify a file descriptor open for |
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output, a redirection error occurs. As a special case, if n is |
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omitted, and word does not expand to one or more digits, the |
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standard output and standard error are redirected as described |
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previously. |
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|
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While the outcome of n>&- is not specified directly in the man page, |
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it is treated exactly as n<&- is. |
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|
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- -- |
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Jonathan Callen |
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