Questions tagged [seekg]
89 questions
0
votes
0 answers
How to overwrite a file after already open?
I'm having the following problem:
my program opens a file and copy all its content to a vector. After that, i need to get back to the beginning of the file and rewrite the content in another order.
I tried using clear and seekp, but it didn't…
user3735796
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0
votes
1 answer
seekg() failing mysteriously
I have a 2884765579 bytes file. This is double checked with this function, that returns that number:
size_t GetSize() {
const size_t current_position = mFile.tellg();
mFile.seekg(0, std::ios::end);
const size_t ret =…
Andreas Bonini
- 44,018
- 30
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0
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2 answers
Problems using seekg in C++
I'm reading a file through a function like this:
#include
#include
#include
...
void readfile(string name){
string line;
int p = 0;
ifstream f(name.c_str());
while(getline(f,line)){
p++;
}
…
Zasito
- 281
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- 17
0
votes
1 answer
fstream seeking: position stays at -1
I constructed a class for dealing in a certain file formal and it's constructor goes through the file and searches for the key information I need - the idea is characters are written on multiple lines, and I want to read the first character of every…
SJWard
- 3,629
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0
votes
2 answers
read and write file in chunks of bytes in c++
I have searched for it everywhere, but I can not seem to understand how to use ios::cur. I need to read a whole file in chunks of 10 bytes, write those bytes into a buffer and then write that buffer into another file. For that I send the first 10…
Basilisk
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0
votes
2 answers
Reading from a particular fill till the last line in C++
I have a text file with many lines. I want to store each line in a vector of strings. I want to read from the file until the last line is reached. I used the EOF function but it seems to store blank lines after the last line also. Here's a snippet…
Manmeet Saluja
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2 answers
Why seekg function doesn't work?
Here's the code:
#include
#include
#include
using namespace std;
int main(int argc, char *argv[])
{
string infile(argv[1]);
ifstream fin(infile.data());
string var_name;
char ch = fin.get();
cout << ch <<…
eaglesky
- 730
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0
votes
1 answer
seekg invalid arguments?
I'm trying to use seekg for the first time.
It says in the documentation it's arguments could be:
istream& seekg ( streampos pos );
istream& seekg ( streamoff off, ios_base::seekdir dir );
From what I understood, 'streampos pos' could be an int? I…
John smith
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0
votes
1 answer
cannot update a field of a record in a relative file, C++
After adding records in the relative file, I am trying to update one field (the balance) of a given record(client) that the user provide the account number. The update happens in the file, but it is not properly done. The output shows that the…
T4000
- 231
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-1
votes
1 answer
Fast accessing file position in ifs() C++
Info: What is the best way to store a position in a txt file, close the file, and later open it at the same position using c++?
I have a large text file that I need to parse in chunks and feed into some system. As of now, I load the file in the…
Sadikov
- 127
- 11
-1
votes
1 answer
How to correctly buffer lines using fread
I want to use fread() for IO for some reason (speed and ...). i have a file with different sized lines. by using a code like:
while( !EOF ){
fread(buffer,500MB,1,fileName);
// process buffer
}
the last line may read incompletely and we have to…
ameerosein
- 523
- 3
- 16
-1
votes
1 answer
Create file using fstream if it doesn't exist that utilizes seekp/seekg?
fstream file(file_1.c_str(), ios::out | ios::in | ios::ate); //convert string to const char*
Error if File does not exist. if ( ! file ) = true
fstream file(file_1.c_str(), ios::out | ios::in | ios::app); //convert string to const char*
using…
Need_Help
- 19
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-1
votes
1 answer
Need help using seekg
I need to write a program that reads certain characters in a file.
For example: all characters from beginning to end or in reverse order. How can I show all characters instead of just one?
//This program reads a file from beg to end, end to beg,…
anonymous1126
- 5
- 1
-3
votes
1 answer
How do I tell a program where to start reading a .txt file?
I want my program to be able to remember where it left off in a .txt file in order to proceed to the next input upon reiteration through a loop.
For instance, a text file containing:
Apples
Bananas
Oranges
would be accessed through a function…
ntjess
- 39
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