For instance: #include <cstdio> NOT #include <stdio.h>In all cases of header files defined by the C language standard prepend with a 'c' and drop the '.h'. But, this applies only to the standard C headers. The Unix/Linux standard header, unistd.h and other header files will still use the older syntax. The reason for this is that in some implementations, the C headers may not be C++ clean. Since I do mostly contract programming, I use the "when in Rome" philosophy, but it also applies to coding. When coding in C, code in C, when coding in C++ code in C++.
-- War story ---Years ago when I worked in COBOL I was given a series of COBOL programs written by a FORTRAN programmer who hated COBOL. While I also knew FORTRAN and BASIC, this was one of the hardest programs I've had to debug, including the Tru64 kernel.
--- End of War story --But, there are times when you need to use C language functions, and they don't know about std::string, iostream, or fstream. In my case I try to wrap these in their own classes, but the bottom line is that there is a task you are trying to accomplish, and it's always important to get it accomplished.
On 02/06/2009 01:54 PM, Shawn O'Shea wrote:
I googled "open file c++" in Google and got this page: http://www.cplusplus.com/doc/tutorial/files.htmlThere's an fstream include and you cin and cout to it like to do to stdin/out.Also, no reason to call out to the shell. All standard file operations (create/delete/copy/move/rename) are usually available natively in a given language. This is true of C/C++. From the same site as above, here's info on the C++ "remove" command:http://www.cplusplus.com/reference/clibrary/cstdio/remove.html -ShawnOn Fri, Feb 6, 2009 at 1:23 PM, <bruce.lab...@autoliv.com <mailto:bruce.lab...@autoliv.com>> wrote:Maybe some on the list might know the answer to this... I am trying to read n files, one at a time, and appending the data to a different file. Since the files are so large, I need to delete each of the n files, once I have captured the data. Why on earth am I doing this? My arrays are too large to fit in memory all at once (I used up all 32GB!!) so I have to process each row of the matrix separately. (It slows stuff way down...) I find string manipulation in C to be a bit arcane. This is what I have come up with so far. Unfortunately, (maybe fortunately?) the compiler does not like my coding. Oh yes, this has to be in a C or C++ dialect. (No "I can do this in x lines of your favorite language" comments. :) ) The code will be compiled using g++ on YDL to run on a QS22 (Cell Processor) = Linux content :) /start code snippet main() { string filename; string shelldelcmd; string mydelstr; char filenum[4]; char filenamec[20]; FILE * fidjj; shelldelcmd.assign("rm -f "); for (jj=0; jj<1000; jj++) { filename.assign("out"); sprintf(filenum, "%04d", jj); //generate string for file number, like "0010" filename.append(filenum); // filename = "outxxxx", where xxxx = jj filenamec = filename.c_str; // <===== COMPILER DIES HERE ========== fidjj = fopen(filenamec, "rb"); // <===== location of second error if (fidjj==NULL) {fputs ("File error, does not exist\n", stderr); exit(1);} fread some stuff... fclose(fidjj); mydelstr.assign(shelldelcmd); mydelstr.append(filename); mydelstr.append("\n"); cout << "my delete string is : " << mydelstr << endl; system(mydelstr); // delete the file I just read... !!! fwrite data to a different file... } } /end code snippet Compiler error is: error; incompatible types of assignment of '<unresolved overloaded function type>' to 'char[20]' If I just use the string "filename" instead of "filenamec" in fopen I get two errors, first the one in the previous paragraph, and second is: error: cannot convert 'std::string' to const char * for argument '1' to 'FILE * fopen(const char *, const char*)' If you think I should step away from the keyboard, well, unfortunately that is not an option. I have to learn this stuff as I go along... And no, I have never taken a class in C++. I barely have the hang of C... FWIW, I tried it in C and suffered some string craziness like unexpected overwriting. It was ugly... This approach seems cleaner, except I do not know how to convert the C++ strings to be able to use ordinary C fopens... Any tips or insight would be greatly appreciated... (Awesome tips are rewarded with beer!)
-- Jerry Feldman <g...@blu.org> Boston Linux and Unix PGP key id: 537C5846 PGP Key fingerprint: 3D1B 8377 A3C0 A5F2 ECBB CA3B 4607 4319 537C 5846
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