Invalid file identifier. Use fopen to generate a valid file identifier.

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Pranav Thiagarajan
Pranav Thiagarajan on 21 Nov 2016
Commented: parivesh meena on 27 Jun 2022 at 23:32
Hello,
I am trying to open a file, skip the first 6 lines (headers) and extract data from the rest of the lines in the file. Here is the code:
%%Declarations
targetinfo(1000)=struct('distance', 0, 'speed', 0, 'angle', 0, 'rcs', 0);
i=1; %index
count=0; %file size counter
[fid, message]=fopen('log.asc','r'); %open log file
%%Read file and extract relevant data
if fid==-1
disp('Error')
else
for k=1:6
header=fgetl(fid); %skip headers
end
while ~feof(fid)
line=fgetl(fid);
if line(16)=='S' || line(13)=='C' || line(1)=='T' %remove control and status signals
continue;
end
id=str2num(line(16:18));
line=line(41:63);
line=line(~isspace(line));
if id==100
canstatus=hex2dec(line(1:2));
targetcount=hex2dec(line(3:4));
canchannel=hex2dec(line(9:10));
else
targetinfo(i).distance=hex2dec(line(1:4));
targetinfo(i).speed=hex2dec(line(5:8));
targetinfo(i).angle=hex2dec(line(9:12));
targetinfo(i).rcs=hex2dec(line(13:16));
end
count=count+1; %increase file size counter
i=i+1; %increase index
fclose(fid); %close file
end
end
I am getting the error I have specified in the title. The value of fid returned is not -1 (it is 4 at the moment) and I do have access to the file, since I can open it in Notepad to view its contents.
I am not opening and closing the file multiple times, just once. Is there any reason I'm missing out?
Thank you for your help.

Accepted Answer

Preethi
Preethi on 21 Nov 2016
hi,
you are closing the file in while loop and trying to access it again. use fclose() after you encountered feof

More Answers (1)

daniel cheng yi lu
daniel cheng yi lu on 28 Nov 2018
For my situation, I have checked everything but missed an easy step.
Please select "Browse for folder" and browse for the folder which the current script is saved, before you run your 'fopen' code.
2018-11-28 (3)_LI.jpg
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