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我正在尝试找到一种简单的方法来打开和关闭对文本文件的日志记录，就像在 Python 中看到的示例一样。他们的解决方案是在需要记录的地方使用有效的文件名，否则使用空设备。 'dev/null'他们正在使用重定向，但我希望使用fopen.

是否有某种方法可以执行以下操作，如果重要的话，哪个词适用于 Unix 或 Windows 系统。

nullFID = fopen('/dev/nul', 'w')

我正在更改的脚本可以通过在某些破坏场景中进行详细记录而受益匪浅，在这些场景中，我们希望为少数文件提取精细级别的详细信息，但对于脚本通常针对的批处理而言，否则会变得太大。

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2 回答 2

4

看起来可以做到这一点，有人在MathWorks上使用类似的“空文件”术语发布了答案。不确定这是否是有效的术语，但可能是“空设备文件”的缩写。

引用空设备的方式取决于操作系统...

nullFID = fopen( 'NUL:'    ); % Windows
nullFID = fopen('/dev/null'); % UNIX

而且似乎参考与 Matlab 版本不同。考虑以下脚本

ver
nullFID = fopen( 'NUL:' , 'w' )
fprintf( nullFID , '12345' )
nullFID = fopen( 'NUL:'  )
fprintf( nullFID , '12345' )
nullFID = fopen('NUL' , 'w' )
nullFID = fopen('NUL' )

以下是从两个版本的 Matlab 生成的输出...

R2011b

>> ver
-------------------------------------------------------------------------------------
MATLAB Version 7.13.0.564 (R2011b)
MATLAB License Number: xxxx
Operating System: Microsoft Windows 7 Version 6.1 (Build 7601: Service Pack 1)
Java VM Version: Java 1.6.0_17-b04 with Sun Microsystems Inc. Java HotSpot(TM) 64-Bit Server VM mixed mode
-------------------------------------------------------------------------------------
MATLAB                                                Version 7.13       (R2011b)

>> nullFID = fopen( 'NUL:' , 'w' )
nullFID = 119

>> fprintf( nullFID , '12345' )
ans = 5

>> nullFID = fopen( 'NUL:' )
nullFID = 120

>> fprintf( nullFID , '12345' )
ans = 0

>> nullFID = fopen('NUL' , 'w' )
Warning: You have chosen a reserved DOS device name for your filename.
Please choose another valid filename
nullFID = -1

>> nullFID = fopen('NUL')
nullFID = -1

R2015a

>> ver
----------------------------------------------------------------------------------------------------
MATLAB Version: 8.5.0.197613 (R2015a)
MATLAB License Number: 1093113
Operating System: Microsoft Windows 7 Professional  Version 6.1 (Build 7601: Service Pack 1)
Java Version: Java 1.7.0_60-b19 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode
----------------------------------------------------------------------------------------------------
MATLAB                                                Version 8.5        (R2015a)

>> nullFID = fopen( 'NUL:' , 'w' )
nullFID = -1

>> fprintf( nullFID , '12345' )
Error using fprintf
Invalid file identifier. Use fopen to generate a valid file identifier.

>> nullFID = fopen( 'NUL:' )
nullFID = 8

>> fprintf( nullFID , '12345' )
ans = 0

>> nullFID = fopen('NUL' , 'w' )
Warning: You have chosen a reserved DOS device name for your filename.
Please choose another valid filename. 
nullFID = -1

>> nullFID = fopen('NUL' )
nullFID = -1
于 2016-02-04T22:09:35.950 回答
3

R2018a

上述建议似乎都不再适用于 R2018a：

>> ver matlab
-----------------------------------------------------------------------------------------------------
MATLAB Version: 9.4.0.813654 (R2018a)
Operating System: Microsoft Windows 10 Pro Version 10.0 (Build 16299)
Java Version: Java 1.8.0_144-b01 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode
-----------------------------------------------------------------------------------------------------
MATLAB                                                Version 9.4         (R2018a)
>> nullFID = fopen( 'NUL:' , 'w' )
Error using fopen
The file name contains characters that are not contained in the filesystem encoding.
 Certain operations may not work as expected.

>> fprintf( nullFID , '12345' )
Undefined function or variable 'nullFID'.

>> nullFID = fopen( 'NUL:' )
Error using fopen
The file name contains characters that are not contained in the filesystem encoding.
 Certain operations may not work as expected.

>> fprintf( nullFID , '12345' )
Undefined function or variable 'nullFID'.

>> nullFID = fopen('NUL' , 'w' )
Warning: You have chosen a reserved DOS device name for your filename.
Please choose another valid filename. 

nullFID =

    -1

>> nullFID = fopen('NUL' )

nullFID =

    -1
于 2018-03-25T13:22:56.750 回答