std::basic_ifstream<CharT,Traits>::is_open
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< cpp | io | basic ifstream
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basic_ifstream::is_open
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bool is_open() const;
Checks if the file stream has an associated file.
Effectively calls rdbuf()->is_open().
[edit] Parameters
(none)
[edit] Return value
true if the file stream has an associated file, false otherwise.
[edit] Example
Run this code
#include <fstream> #include <iostream> #include <string> // this file is called main.cpp bool file_exists(const std::string & str) { std::ifstream fs(str); return fs.is_open(); } int main() { std::boolalpha (std::cout ); std::cout << file_exists("main.cpp") << '\n' << file_exists("strange_file") << '\n'; }
Possible output:
true false
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 365 | C++98 | is_open was not declared with const qualifier
|
declared with const qualifier |