Check if filename is valid.

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Qingyang
Qingyang 2012-7-20
编辑： Voss 2023-12-19
Hi, is there a native function or a simple code to check if a user-typed filename is valid for saving a file? (In that it doesn't contain illegal characters like /\":?<>|, etc.)

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采纳的回答

Sean de Wolski
Sean de Wolski 2012-7-20
regexp it!
  4 个评论
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Jason Nicholson
Jason Nicholson 2014-2-14
This code snippet will not work unless you check if it is empty.
if ~isempty(regexp(filename, '[/\*:?"<>|]', 'once'))
%Do something
end
Voss
Voss 2023-12-19
编辑：Voss 2023-12-19
Ran in:
You need to escape the backslash in the regular expression for that to work right:
~isempty(regexp('file\name','[/\*:?"<>|]', 'once')) % no match
ans = logical
0
~isempty(regexp('file\name','[/\\*:?"<>|]', 'once')) % match
ans = logical
1
Of course, on Windows, if absolute or relative path names are allowed, then backslash is a valid character, and if absolute path names are allowed, then colon is a valid character. On Mac/Linux, if absolute or relative path names are allowed, then slash is a valid character.

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更多回答（5 个）

Daniel Shub
Daniel Shub 2012-7-23
A long time ago, probably Windows 95 on a FAT16 harddisk, I started using the following:
regexp(fname, ['^(?!^(PRN|AUX|CLOCK\$|NUL|CON|COM\d|LPT\d|\..*)', ...
'(\..+)?$)[^\x00-\x1f\\?*:\"><|/]+$'], 'once'));
At that time, Windows had the most restrictive file name conventions. I am not sure what the rules are now. You also should check for the length of the path and the total number of characters in the file name.
  1 个评论
Jan
Jan 2012-7-23
Windows 7: Either 260 characters, or start with //?/ and 32767 characters, while each folder can have up to 255 characters. The later works for most of the API-functions, but not e.g. for the Windows Explorer. Moving a file name with a long name to the RecycleBin fails also. The backup program and server based tools might fail also. Therefore I'd prefer the dull limit of 260 characters (including "C\:" and a trailing terminator '\0')!).

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ola bayo
ola bayo 2017-10-16
编辑：Walter Roberson 2017-10-16
Which following is a valid file name in MATLAB?
A) lab 2
B) lab2
C) lab-2
D) 2lab
E) LAB 2
  1 个评论
Walter Roberson
Walter Roberson 2017-10-16
For the question as phrased: all of them. For a slightly different question, the answer would be fairly different.

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Thomas
Thomas 2017-12-1
If you do not want to use UIputfile, another option is fopen. fileID = fopen(filename,'w') if fopen cannot open the file, then fileID is -1.
Daniele Busi
Daniele Busi 2020-2-24
function bool = isLegalPath(str)
bool = true;
try
java.io.File(str).toPath;
catch
bool = false;
end
end
George Abrahams
George Abrahams 2023-12-19
编辑：George Abrahams 2023-12-19
Hi Qingyang, I recently released the isvalidpath function on File Exchange which does exactly this!
Like @Daniele Busi's answer, it's based on java.io.File().toPath, which is more robust than anything we'll build ourselves, but isvalidpath also provides:
  • The option to validate that the path refers to a file, rather than a directory, or vice versa.
  • The option to validate that the file extension matches a given set, for example, that the path refers to an image.
  • Human readable feedback, in case the validation fails, for example, a warning that the path lacks a filename or contains an illegal character.

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