Carriage return not detected with fopen

Question

Matthieu Magnon 2019-5-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/462221-carriage-return-not-detected-with-fopen

评论： Matthieu Magnon 2019-5-16

Hi all,

I want to parse information in a text file, the file as the following structure:

nb_elements = 715
x_step_inv = 572.9578
-0.6170 -0.0440
-0.6160 -0.0770
[other rows...]
nb_elements = 123
x_step_inv = 572.9578
-0.6170 -0.0440
-0.6160 -0.0770
[other rows...]
nb_elements = 456
x_step_inv = 572.9578
-0.6170 -0.0440
-0.6160 -0.0770
[other rows...]
 

Each new line is ended by "\n" when writted in a c file. For example all 'nb_elements' lines are:

fprintf(fp, "nb_elements = %d\n", nb_elements); /* c file code */

When opened with vim, the result is:

On Matlab is use the following code:

fileID = fopen(file_path, 'wt');
A = fscanf(fileID, 'nb_elements = %d\n');
fclose(fileID):

But A is empty, it should at least returns the first nb_element value equal to 100

I have also tried below commands wtihout success:

A = fscanf(fileID, 'nb_elements = %d\r\n');
A = fscanf(fileID, 'nb_elements = %d\r');

I don't know why fscanf don't parse specified format data, any idea is welcome (I use Matlab on a Linux machine)

Matt

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2019-5-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/462221-carriage-return-not-detected-with-fopen#answer_375107

Opening a file with 'wt' tells matlab to erase the content of the file and prepare to write it with cr nl termination. You need 'r' or 'rt' for reading.

3 个评论
显示 1更早的评论隐藏 1更早的评论

Walter Roberson 2019-5-15

fopen only once. That positions at the beginning of the file when you ask for read permission. Each fgets or fgetl or fread moves forward from the last position unless a fseek is used (or some circumstances involving having opened with different permissions)

Matthieu Magnon 2019-5-16

Sorry my message was unclear: I call fopen only once, I just request an other string pattern.

To resume: altough the pattern "x_step_inv = %f\n" in present several times in the file, but the resulting commend is still empty. And for the pattern "nb_elements = %d\n", only the first occurrence is detected, not the other ones.

请先登录，再进行评论。