fstreams - read si write in acelasi timp

#1
Sess

Posted 03 December 2016 - 11:14

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Înscris: 20.01.2016

Salut,

Am urmatorul cod:

#include <iostream>
#include <stdlib.h>
#include <fstream>
#include <string>
using namespace std;
int main()
{
fstream f("test.txt", ios::in | ios::out | ios::app);
if (!f)
{
cout << "File won't open!\n\n";
system("pause");
return 1;
}
f << "Line 1\n";
f << "Line 2\n";
while (f)
{
string line;
getline(f, line);
cout << line<<endl;
}
system("pause");
f.close();
return 0;
}

Cand rulez codul de mai sus, imi scrie in fisier cateva linii de genu:

Quote

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Daca folosesc fluxurile separat de citire si scriere, totul functioneaza corect.

Ce anume imi scapa la codul de sus?

Multumesc.

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#2
Axel2015

Posted 03 December 2016 - 11:29

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f << "Line 1\n";
f << "Line 2\n"
F << ''Line 3\n''

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#3
Sess

Posted 03 December 2016 - 11:39

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Axel2015, on 03 decembrie 2016 - 11:29, said:

f << "Line 1\n";
f << "Line 2\n"
F << ''Line 3\n''

Nu inteleg.

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#4
dani.user

Posted 03 December 2016 - 11:48

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Posts: 30,251
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Ce incerci sa rezolvi folosind read si write in acelasi timp?

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#5
Sess

Posted 03 December 2016 - 11:52

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Vreau sa folosesc acelasi flux de intrare si de iesire deoarece codul pare mai curat si mai usor de inteles. Pe de alta parte, daca C++ ofera posibilitatea asta, de ce nu?

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#6
dani.user

Posted 03 December 2016 - 12:54

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Cod care face ce mai exact? Daca vrei doar sa recitesti ce scrii, exista stringstream ce face totul in memorie (nu mai freaca discul).

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#7
Sess

Posted 03 December 2016 - 13:09

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dani.user, on 03 decembrie 2016 - 12:54, said:

Cod care face ce mai exact? Daca vrei doar sa recitesti ce scrii, exista stringstream ce face totul in memorie (nu mai freaca discul).

E doar un exemplu basic ce am postat. Imi poti spune ce anume e gresit? Compilatorul nu arunca nicio eroare.

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#8
dani.user

Posted 03 December 2016 - 13:41

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E derutat streamul. Pune

f.seekg(0, ios_base::beg);

dupa ce ai scris si inainte de a citi pentru a-i indica ca vrei sa citesti de la inceput.

Deasemenea, trebuie sa verifici daca e ok streamul dupa ce ai apelat getline, nu inainte

string line;
while (getline(f, line))
{
   cout << line << endl;
}

Edited by dani.user, 03 December 2016 - 13:47.

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#9
Sess

Posted 04 December 2016 - 12:43

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Multumesc frumos!

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fstreams - read si write in acelasi timp

#1 Sess Posted 03 December 2016 - 11:14

#2 Axel2015 Posted 03 December 2016 - 11:29

#3 Sess Posted 03 December 2016 - 11:39

#4 dani.user Posted 03 December 2016 - 11:48

#5 Sess Posted 03 December 2016 - 11:52

#6 dani.user Posted 03 December 2016 - 12:54

#7 Sess Posted 03 December 2016 - 13:09

#8 dani.user Posted 03 December 2016 - 13:41

#9 Sess Posted 04 December 2016 - 12:43

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#1
Sess

Posted 03 December 2016 - 11:14

#2
Axel2015

Posted 03 December 2016 - 11:29

#3
Sess

Posted 03 December 2016 - 11:39

#4
dani.user

Posted 03 December 2016 - 11:48

#5
Sess

Posted 03 December 2016 - 11:52

#6
dani.user

Posted 03 December 2016 - 12:54

#7
Sess

Posted 03 December 2016 - 13:09

#8
dani.user

Posted 03 December 2016 - 13:41

#9
Sess

Posted 04 December 2016 - 12:43