new_name). Note: The recommended signature of main() is int main(int argc, char *argv[]). How to append text to a text file in c++? The difference is the {} at the end of char c[256]{}. Here, I've used an exception, but you can use error handling of your choice, if this is not an option for you. String literals are constant and shouldn't be modified, older compilers might allow assigning them to char * but more modern compilers will only allow assignment to const char* (or const char[]), e.g. Step 3 - Use the memcpy() function to copy the const char* to the char*. pointers - convert char* to const char* in C++ - Stack Overflow const char* original = "TEST"; char* copy; copy = original; original points to the start of the string "TEST", which is a string literal and thus points to read-only memory. To learn more, see our tips on writing great answers. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Could a subterranean river or aquifer generate enough continuous momentum to power a waterwheel for the purpose of producing electricity? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. In doing so, terminating \0 was not copied. C++ : How to convert 'wchar_t *' to 'const char *' - YouTube const char* dllPaths[] = { "C:\\mydll.dll" }; and i want to append a new item to it so it will be { "C:\mydll.dll", "the thing i want to append"} So far i tried to use a buffer to store the new array and then to delete the dllPaths variable from the memory and then to realocate the new array but did not worked. There are many different ways to copy a const char* into a char []: #include <cstring> const char *s = "x"; char c [256] {}; std::strncpy (c, s, 255); #include <algorithm> #include <cstring> const char *s = "x"; char c [256] {}; std::copy_n (s, std::min (std::strlen (s), 255), c); What were the most popular text editors for MS-DOS in the 1980s? You can't put character pointers in EEPROM and expect the characters they used to be pointing at to still be there when you read the pointer back into memory. If you name your member function's parameter _filename only to avoid naming collision with the member variable filename, you can just prefix it with this (and get rid of the underscore): If you want to stick to plain C, use strncpy. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Has the Melford Hall manuscript poem "Whoso terms love a fire" been attributed to any poetDonne, Roe, or other? and MyEepromArray[12] is still an array of pointers, char *, not char, MyEepromArray[12] is still an array of pointers, char *, not char, it's correct You need to pre-allocate the memory which you pass to strcpy. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. @keanehui1 no. How about saving the world? No. Thanks for contributing an answer to Stack Overflow! How to Make a Black glass pass light through it? Pointers point to other parts of memory which must, in of themselves, exist. Without any attempt at completeness or educational direction, here's a version of your code that should work. c_str returns a const char* that points to a null-terminated string. There are many different ways to copy a const char* into a char[]: Is bad code. How to call qdebug without the appended spaces and newline in C++? That is the second parameter does not have qualifier const. English version of Russian proverb "The hedgehogs got pricked, cried, but continued to eat the cactus". Even when you do, you will probably overwrite unallocated memory when you attempt to set the string terminator. Solution: allocate memory for new_name. What is the difference between const int*, const int * const, and int const *? Use a std::string to copy the value, since you are already using C++. Thanks for contributing an answer to Stack Overflow! I'm trying to copy only a portion of a string (or char *) into another string (or another char *) char * first_string = "Every morning I" char * second_string = "go to the library, eat breakfast, swim." char * final_string; I would like to copy part of the second_string into the first_string. Copying strings is an expensive operation. Find centralized, trusted content and collaborate around the technologies you use most. Counting and finding real solutions of an equation, Generating points along line with specifying the origin of point generation in QGIS, A boy can regenerate, so demons eat him for years. str0 = (char*) str1; or use std::string class template library for managing strings.std::string owns the character buffer that stores the string value. You need to copy some bytes from one place to another, where you have pointers to both locations. Fixed it by making MyClass uncopyable :-). Has the Melford Hall manuscript poem "Whoso terms love a fire" been attributed to any poetDonne, Roe, or other? If you really want the raw point out of an std::string you can use the c_str() method and it will return you a const char* - I strongly advise against it, unless you have to pass it to a function that only accepts const char*. Why is char[] preferred over String for passwords? you are to fast! why no overflow warning when converting int to char. What does "up to" mean in "is first up to launch"? What were the most popular text editors for MS-DOS in the 1980s? Does the 500-table limit still apply to the latest version of Cassandra? It works now, however it says that strncpy is a function on char but I'm using the sizeof char *. Secondly argv[1] has type char *. int main(int argc, char *argv[]) ^^^^^ That is the second parameter does not have qualifier const.. Secondly argv[1] has type char *.There is no any sense to compare it with a character literal similar to '1234'.As for string literal "1234" when it may not be used in the case label. You can either call malloc() and then use strcpy(), or call strdup() which will do both things for you: See this answer for more details on strdup(): https://stackoverflow.com/questions/252782/strdup-what-does-it-do-in-c. You need to allocate space for the new string. - Zdeslav Vojkovic Sep 28, 2012 at 10:30 So: The problem is that you're using strncpy, rather than strcpy. What is the difference between char * const and const char *? error say it can't be converted const char [13] to char * . Easiest way to convert int to string in C++, error: passing xxx as 'this' argument of xxx discards qualifiers. Appending to a const char* array in c++ - Stack Overflow Understanding the probability of measurement w.r.t. What is the difference between const int*, const int * const, and int const *? @JaviMarzn It would in C++, but not in C. Some even consider casting the return of. i will study this carefully. Array : Syntax for passing a const char parameter to static char *argv[] in CTo Access My Live Chat Page, On Google, Search for "hows tech developer connect". It is at least as safe (and often safer) and more efficient if done properly. Sure, my point was it was hypocritical to criticize the strncpy answer doing extra work is since your own example does extra work. Gahhh no mention of freeing the memory in the destructor? To prevent possible type overflow you could do this: const char char_max = (char) ( ( (unsigned char) char (-1)) / 2); int i = 128; char c = (i & char_max); // Would always result in positive signed values. i did studied this for hours, just need a hint. Is there a generic term for these trajectories? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. casting int to char using C++ style casting - Stack Overflow Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, Is it a good practice to free memory via a pointer-to-const, How to convert a std::string to const char* or char*. Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? Find centralized, trusted content and collaborate around the technologies you use most. Here's an example of what I'm working with: I have a const char *, I need to set the "name" value of test to the const char. It is always wrong. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Find centralized, trusted content and collaborate around the technologies you use most. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. How to combine several legends in one frame? You need to start with a basic C tutorial. Otherwise, you can allocate space (in any of the usual ways of allocating space in C) and then copy the string over to the allocated space. Easiest way to convert int to string in C++. If total energies differ across different software, how do I decide which software to use? I agree that the best thing (at least without knowing anything more about your problem) is to use std::string. Of course one can combine these two (or none of them) if needed. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Since you manually have to repair the corner case, you could just as well use memcpy in the first place. Asking for help, clarification, or responding to other answers. So now what s points to is undefined, If you were not creating the string in that line it would be safe. Does a password policy with a restriction of repeated characters increase security? Problem with this answer is if s is more than 255 characters there will be no terminating 0 at the end of c. Whether that's important or not is really up to you but 999 times out of 1000 it probably is important. What does "up to" mean in "is first up to launch"? Thanks for contributing an answer to Stack Overflow! Is there a generic term for these trajectories? What was the actual cockpit layout and crew of the Mi-24A? Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? printMe takes an lvalue reference to a mutable pointer to const char.