"clear all" causing annoying warning messages

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Sarah T
Sarah T 2017-8-8
移动：Stephen23 2024-4-10
I am using "clear all" at the start of a ".m" file that I have written myself (lets call it "myfile.m"). When I run the file, I get three identical messages stating "Warning: The file 'myfile.m' could not be cleared because it contains MATLAB code that is currently executing." I don't want to turn warnings off, because I am writing my own warnings later in the file. Why does this happen and how can I prevent it? I am using Matlab version 2017a.
  2 个评论
KSSV
KSSV 2017-8-8
Are you sure Clear all is placed only at the start of the code?
Stephen23
Stephen23 2017-8-8
编辑：Stephen23 2017-8-8
"clear all" causing annoying warning messages"
Putting clear all at the top of every script is one of the most common signs of cargo-cult programming in MATLAB. The best solution is: do not put clear all at the top of every mfile, and learn to write functions. Problem solved!
Search this forum to know more about why putting clear all everywhere is a bad practice (as you are starting to find out):
https://www.mathworks.com/matlabcentral/answers/272064-difference-between-clear-and-clear-all
https://www.mathworks.com/matlabcentral/answers/329964-how-to-clear-all-variables-of-a-workspace-except-for-those-explicitly-excluded
https://www.mathworks.com/matlabcentral/answers/43497-the-command-clc-and-clear-all-does-not-work-on-a-script-in-the-editor#answer_53402
https://www.mathworks.com/matlabcentral/answers/344338-clc-clear-all
https://www.mathworks.com/matlabcentral/answers/57361-hi-i-stuck-in-basics-of-matlab-function-command
https://www.mathworks.com/matlabcentral/answers/59375-can-i-use-2-push-buttons-to-start-and-stop-this-code-of-mine
http://blogs.mathworks.com/pick/2013/07/19/clear-everything/
https://www.mathworks.com/matlabcentral/answers/302898-what-do-you-think-of-did-you-mean-clearvars-except
etc, etc, etc.

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采纳的回答

Jan
Jan 2017-8-8
clear all clears Matlab's memory in a brutal way. While removing all locally used variables might be useful for scripts, which are short hacks or prooves of concept, it is evil is productive code. Prefer clean workspaces by using functions instead.
Then clear all deletes all functions from the RAM, and the reloading from the slow hard disk wastes a lot of time. Doing this frequently means a massive loss of speed. In your case Matlab warns, that some functions cannot be removed. Perhaps they are callbacks of GUIs or timers, or the currently processed M-code.
In addition all persistent variables are cleared and many functions need a time-consuming re-initialization afterwards.
In older Matlab versions clear all has deleted all debugger breakpoints also, and anything, which impedes debugging is an enemy of teh programmer.
The solution is trivial: Omit the evil clear all. Instead of hiding the warning message, this is much more efficient.

更多回答（1 个）

David Cazenave
David Cazenave 2024-4-9
移动：Stephen23 2024-4-10
You can still turn off the warnings, and then turn them back on before your 'custom warnings.' If that helps, Thank you ... Thank you very much.

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