This question already has an answer here:
Will the attempt to read an improper value into a variable change its value?
(1 answer)
Closed 7 years ago.
When reading from a file using the following command, and get iostat value to be eof, is the data from s valid or should I discard it?
Read (u, "(a)", iostat=st) s
Upon an end of file condition for a READ statement, all variables in the input list become undefined. See F2008 9.11.3 item (3).
Related
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Strange numbers when array is not initialized in C++ [duplicate]
(3 answers)
What happens to a declared, uninitialized variable in C? Does it have a value?
(9 answers)
Closed 1 year ago.
I have tried a simple code and found a strange error(wrt me)
it is something like s[10]
now i have put some number of values into this array.t
like s[0]=0;s[1]=1.s[2]=2 and all others are empty.
now i put a for loop to see how it goes and to my surprise after index 2, some random numbers popping up in output and idk why. It should be null and the loop should have exited but here, it gives me some output like 01248766575...
why is it happening? pls do help me if u know
This question already has answers here:
Why is iostream::eof inside a loop condition (i.e. `while (!stream.eof())`) considered wrong?
(5 answers)
Closed 7 years ago.
So i'm reading in a input file that contains:
lololololololol
I need to read it in using binary one byte at a time for something I'm doing later on. To do this i'm using get() to read it in then storing it into a char. It seems to be working correctly except for the last char that it reads in. The vector that it is reading into contains:
lololololololol
�
I'm not quite sure what this last value is but it's totally throwing off my finial output. So my question is, is there a reason get() would read in a value or byte from my text document that is not there? Or is it reading in something that I don't know of?
code:
while(istr.good()) {
temp = istr.get();
input.push_back(temp);
}
It's reading the EOF (end of file) character. You need to do the check after reading it to avoid it being inserted to the vector:
while(temp = istr.get(), istr.good()) // comma operator
input.push_back(temp);
Or you might use the 2nd std::istream_base::get overload and let istr implicitly convert to bool:
while(istr.get(temp))
input.push_back(temp);
Or try more advanced approaches. operator>> and std::getline would also work fine for this kind of input.
This question already has answers here:
Why is iostream::eof inside a loop condition (i.e. `while (!stream.eof())`) considered wrong?
(5 answers)
Closed 7 years ago.
I am reading in from an input file "input.txt" which has the string 'ABCDEFGH' and I am reading it in char by char. I am doing this using the code:
ifstream plaintext (input.txt);
char ch;
if (plaintext.is_open())
{
while(!plaintext.eof()){
plaintext.get(ch);
cout<<ch<<endl;
}
plaintext.close();
}
The string 'ABCDEFGHH' is printed out. I have no idea why it is printing 'H' twice. Any help would be appreciated. I got this code example from HERE
This is because the EOF test does not mean "our crystal ball tells us that there are no more characters available in this tream". Rather, it is a test which we apply after an input operation fails to determine whether the input failed due to running out of data (EOF) or some other condition (an I/O error of some sort).
In other words, EOF can be false even after we have successfully read what will be the last character. We will then try to read again, and this time get will fail, and not overwrite the existing value of ch, so it still holds the H.
Streams cannot predict the end of the data because then they could not be used for communication devices such as serial lines, interactive terminals or network sockets. On a terminal, we cannot tell that the user has typed the last character they will ever type. On a network, we cannot tell that the byte we have just received is the last one. Rather, we know that the previous byte was the last one, because the current read operation has failed.
This question already has answers here:
Writing multiple output files in Fortran
(2 answers)
Closed 8 years ago.
I want to open a file in fortran with file name "controlinputs.12.dat" and then write into that file. The digit "12" is user defined variable whose value is stored in another variable "k". I have tried following and failed.
k=12
open(10,filename='controlinputs.',k,'.dat')
Tried storing the name in character and then using character to open file.
k=12
fname='controlinputs.',k,'.dat'
open(10,filaname=fname)
This was very simple. I didn't knew how to concatenate characters. I was reading the integer 12 from a file so I saved it in character type then simply used following.
character::k*5
open(10,filename='controlinputs.'//trim(k)//'.dat')
This question already has an answer here:
what does DATA TKX/2HKX/ mean in fortran?
(1 answer)
Closed 1 year ago.
Does anyone know the meaning of 4HEND in the following line which comes from an old Fortran code?
DATA XHEND / 4HEND /
4HEND is a Hollerith code to represent the character string "END ". In very old FORTRAN, the variable XHEND might even be a 4-byte integer or real used to hold character data. If implicit typing was in effect in this program, XHEND would have been a real. Another recent question with Hollerith codes: Writing both characters and digits in an array
It replaces assignment
XHEND='END '