Thread Subject: change in *.txt file

I hope to get help/direction on this.

so I have a 'input.txt' file that contains a line such as:
command 1

Now, I want to change that value, '1', to something else, for example i=1:1:10, so replacing i for each run, I can save a new input.txt file. I can have
command 1
command 2
...
command 10
I'm not sure what exact matlab command for doing this. Could you suggest some?

Another question is....
I use fopen(fid,'w') but this create a new file. So I lost all other lines that I don't want to change beside the line 'command 1'. My solution for this is to copying all input.txt to input1.txt and copy all lines from input1.txt to input.txt when I fopen(input, 'w'). Then manually, individually change only the 'command 1' line. Do you know a better solution for this?

Thanks in advanced.

Hello,

There could be better solutions, but one straight-forward solution is the following:

fread everything in the txt file to be of type char. This should give you a vector. Then, you can change the element of the vector corresponding to the character you would like to change. For example, if your txt file begins with command 1, then the character you would like to change is the 9th character [As in A(9) = '2';]. Once you make this change, you can then write this whole character array into a new file.

Best.

"Khanh " <kdcung@mtu.edu> wrote in message
news:j5meo5$4ff$1@newscl01ah.mathworks.com...
> I hope to get help/direction on this.
>
> so I have a 'input.txt' file that contains a line such as:
> command 1
>
> Now, I want to change that value, '1', to something else, for example
> i=1:1:10, so replacing i for each run, I can save a new input.txt file. I
> can have
> command 1
> command 2
> ...
> command 10
> I'm not sure what exact matlab command for doing this. Could you suggest
> some?
>
> Another question is....
> I use fopen(fid,'w') but this create a new file. So I lost all other lines
> that I don't want to change beside the line 'command 1'. My solution for
> this is to copying all input.txt to input1.txt and copy all lines from
> input1.txt to input.txt when I fopen(input, 'w'). Then manually,
> individually change only the 'command 1' line. Do you know a better
> solution for this?

Open the file in 'append' mode using the 'a' option.

--
Steve Lord
slord@mathworks.com
To contact Technical Support use the Contact Us link on
http://www.mathworks.com

Thank you for your suggestions. I have worked it out. I simply create a new copy of the file I want to edit, then use fwrite to copy/edit all the lines I want.


"Khanh" wrote in message <j5meo5$4ff$1@newscl01ah.mathworks.com>...
> I hope to get help/direction on this.
>
> so I have a 'input.txt' file that contains a line such as:
> command 1
>
> Now, I want to change that value, '1', to something else, for example i=1:1:10, so replacing i for each run, I can save a new input.txt file. I can have
> command 1
> command 2
> ...
> command 10
> I'm not sure what exact matlab command for doing this. Could you suggest some?
>
> Another question is....
> I use fopen(fid,'w') but this create a new file. So I lost all other lines that I don't want to change beside the line 'command 1'. My solution for this is to copying all input.txt to input1.txt and copy all lines from input1.txt to input.txt when I fopen(input, 'w'). Then manually, individually change only the 'command 1' line. Do you know a better solution for this?
>
> Thanks in advanced.