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Please let me know if I have to correct certain points or if we can do better than with the presented solutions (thanks again to Alexandre at this point). Thank you! Here's a nearly-complete demo program; arranging to reliably remove the test directory if and only if you created it, I leave as an exercise. #include #include #include #include ncurses Related 2Why ofstream would fail to open the file in C++?

if the file does not exist or if it is a directory or if the executing process is not allowed to access the file? EvenSt-ring C ode - g ol!f Is 'if there's any' grammatical in this sentence? What does it mean for meth to be 'pure'? I agree, this is normal procedure.

If you do not want to ignore that line, do not consider eofbit to be a failure (i.e., do not check the stream's state with good()). cerr << "Error code: " << strerror(errno); // Get some info as to why seems relevant to the question. –Matthieu Rouget Jun 27 '13 at 8:28 @MatthieuRouget: Check the tl;dr: here is your fish, have at it. > Perror reads the global variable errno to figure out > the problem. If the pathname is too long.

We for example expect that when fopen() returns NULL, errno is set to something meaningful. asked 2 years ago viewed 5266 times active 2 years ago Related 3Reading in a file and performing string manipulation5Reading the contents of an XPI file8Validation/error handling of user input values3Program You try to create a directory. Only a set badbit identifies an exception.

Share this:Tweet This entry was posted in C/C++, Linux, Software architecture, Technology on June 25, 2011 by Jan-Philip Gehrcke. The point is: in each iteration, the chronological order of IO operation, error check, and data processing is preserved. Start a new discussion instead. May be a good opportunity to dive into the libstdc++ source code :-) –Matthieu Rouget Jun 27 '13 at 9:17 I tried this out: Tried to open a nonexisting

else do something else..... g++ $COMPILATION_SOURCE # Create test files / directories and put them in the desired state. if fileName doesn't exist. If a component of the pathname is not a directory.

Right? With modern technology, is it possible to permanently stay in sunlight, without going into space? If they give me a bad file name, it doesn't work. Argument mode specifies the opening mode.

libc++ // http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/ios?revision=193085&view=markup // (line 415) // // and not keeps on deriving it directly from runtime_error // like libstdc++ // https://github.com/mirrors/gcc/blob/master/libstdc%2B%2B-v3/include/bits/ios_base.h#L209 // cout << "libc++ error #" << e.code().value() << This is ancient. if (!f.is_open()) perror(("error while opening file " + filename).c_str()); // Read the file via std::getline(). That is, on POSIX-compliant systems errno/perror is thread-safe.

If, while opening a device file, you press CTRL-C. If you don't have search permission on some parent directory. Sometimes, however, meaningful error messages must be emitted. After the investigation described below, I am pretty sure that the simplest rock-solid language construct for above-specified task is: string line; ifstream f ("file"); while(getline(f, line)) { process(&line); } This is

Furthermore, I must have missed something while evaluating the test results on a file like "foo\nbar"… I was quite sure that I always noticed the failbit together with eofbit. The message I get when I give it a bogus filename is: terminate called after throwing an instance of 'char*' Abort trap #include #include #include int main(int argc, This page has been accessed 27,800 times. Hence, the error message can be made precise.

Rules obeyed: // - first the I/O operation, then error check, then data processing // - failbit and badbit prevent data processing, eofbit does not while(getline(f, line)) { process(&line); } // You haven't tried to read lines from a binary file like an executable. Santosh In my c++ code I used is_open(), when I am running this code on Solaris 10 multi-core system I am facing issue. Either: try { std::ifstream somefile(argv[1], std::ios::in|std::ios::binary ) ; if( !file ) throw "Error opening file!" ; // no error // ... } catch( const char* cstr ) { std::cerr << cstr

But I agree with you -- one must not rely on that. Theoretically should work equally well on Linux too since it relys only on what C/C++ language standard and library documentation says. Jan-Philip Gehrcke Why don't you, for starters, try if any of my examples work with your compiler (I've been using GCC on Linux, what are you using?)? Also, some of your arguments are plain wrong.

While doing so, the goal was to handle all underlying stream errors as well as file opening errors, and to emit as precise error messages as possible. Why is water evaporated from the ocean not salty? The goal is to process the data read from the file, line by line, via the fictitious call to process(line). error state: Is a directory stream badbit.

asked 7 years ago viewed 12156 times active 1 year ago Get the weekly newsletter! error state"); else cout << "is_open() returned true." << endl; cout << "* checking error bits once before first getline" << endl; check_error_bits(&f); while(1) { cout << "* perform getline() # I have two tables, I will call them first-half and second-half (of the year) Table: first id jan feb mar apr ----------------------- 2 80 90 70 60 3 50 40 60 To read it you'd need to use the OS's primitives for reading directories - that's what "ls" is doing after all (and maybe open it in binary mode?

Unfortunately, the standard does not state that open() sets errno, so you can't absolutely depend on it. –anon Jun 6 '09 at 22:06 Seems to work in VS2013 Update I also noticed that the error messages returned by std::ios::failure are pretty useless. –jliv902 Jul 24 '14 at 19:00 add a comment| 2 Answers 2 active oldest votes up vote 4 ios::binary). Both will probably platform dependent. –Arne Mertz Jun 27 '13 at 9:10 @AlexFarber: I think that Arne's answer is better than mine.

But where is this actually documented? Already in the Single Unix Specification 2 (1997) it was clarified that errno is thread-safe [1]: For each thread of a process, the value of errno shall not be affected by Appease Your Google Overlords: Draw the "G" Logo Is there any job that can't be automated? Did you test that?

Linked 4 Program crashes after opening file 0 Filestreams won't open 0 opening output filestreams with string names 0 Why doesnt this write to a file and why isn't this producing The code snippet above cannot be surprised. assist. That's why I didn't post ;) –arne Jun 27 '13 at 9:43 @arne wich platform, compiler, os? –Arne Mertz Jun 27 '13 at 10:04 | show 3 more comments