这个写法:>代表什么意思？

sunauqt

看到一段代码，如下

cd $SLOWLOGDIR
    cp -f slow-query.log ${LDATE}-slow.log
    :>slow-query.log
    rm -f ${lastmonth}-slow.log

请教各位，:>代表什么意思？

waker

1. 
   
2. : [arguments]
   
3. No effect; the command does nothing beyond expanding arguments and performing any specified redirections. A zero exit code is returned.
   

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1. 
   
2. Redirecting Output
   
3. 
   
4. Redirection of output causes the file whose name results from the expansion of word to be opened for writing on file descriptor n, or the standard output (file descriptor 1) if n is not specified. If the file does not exist it is created; if it does exist it is truncated to zero size.
   
5. The general format for redirecting output is:
   
6. 
   
7. [n]>word
   
8. If the redirection operator is >, and the noclobber option to the set builtin has been enabled, the redirection will fail if the file whose name results from the expansion of word exists and is a regular file. If the redirection operator is >|, or the redirection operator is > and the noclobber option to the set builtin command is not enabled, the redirection is attempted even if the file named by word exists.
   

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