R2018a

Question

我正在尝试找到一种简单的方法来将日志记录打开和关闭，就像Python中的here示例一样。他们的解决方案是使用需要记录的有效文件名，否则使用null device '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')

我正在改变的脚本可以通过在某些突发场景中详细记录来获益，在这些场景中我们希望为少量文件提取精细的详细信息，但是对于脚本通常目标的批处理而言，这会非常大

Answer 1

看起来可以这样做，有人在MathWorks上使用类似术语“空文件”发布了答案。不确定这是否是有效的术语，但可以缩短“空设备文件”。

引用空设备的方法是依赖于OS ...

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

此外，该参考文献似乎与Matlab版本不同。请考虑以下脚本

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

以下输出是从两个版本的Matlab生成的......

<强> 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

<强> 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

Answer 2

R2018a

以上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

Matlab中是否有空设备？

2 个答案:

R2018a