Check if filename is valid.

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Qingyang
Qingyang on 20 Jul 2012
Answered: Daniele Busi on 24 Feb 2020
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.)

Accepted Answer

Sean de Wolski
Sean de Wolski on 20 Jul 2012
regexp it!
  3 Comments
Jason Nicholson
Jason Nicholson on 14 Feb 2014
This code snippet will not work unless you check if it is empty.
if ~isempty(regexp(filename, '[/\*:?"<>|]', 'once'))
%Do something
end

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More Answers (4)

Daniel Shub
Daniel Shub on 23 Jul 2012
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 Comment
Jan
Jan on 23 Jul 2012
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 on 16 Oct 2017
Edited: Walter Roberson on 16 Oct 2017
Which following is a valid file name in MATLAB?
A) lab 2
B) lab2
C) lab-2
D) 2lab
E) LAB 2
  1 Comment
Walter Roberson
Walter Roberson on 16 Oct 2017
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 on 1 Dec 2017
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 on 24 Feb 2020
function bool = isLegalPath(str)
bool = true;
try
java.io.File(str).toPath;
catch
bool = false;
end
end

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