You can add a string to a buffer pointed to by a char pointer IF there is sufficient allocated space in the buffer (plus one for the terminating '\0') using a standard library call such as strncpy() [depends on your precise requirements, insert versus append etc]. Not the answer you're looking for? Is a dropper post a good solution for sharing a bike between two riders? This will help others answer the question. I haven't seen your code so I can't tell you why it hangs. You need to initialize it, for example with: This is ok if you've initialized p to point somewhere -- except that you can overflow the buffer it points to if you enter too much data. Concat strings, assign to char pointer - C++ Forum - C++ Users Is speaking the country's language fluently regarded favorably when applying for a Schengen visa? Here q is just a char, so this prints its value as a character: h. the string literate will be stored in .rdata section which will be read only so reading into it with std cin would crash the program, then the pointer p points to an allocated and read only memory , as the rdata section will be surely allocated and prepared by the windows loader , but as I said .rdata can't be modified. Here ptr is pointer to a character. p is a pointer, but you haven't initialized it, so it could point anywhere or nowhere. rev2023.7.7.43526. Property of twice of a vector minus its orthogonal projection, Finding K values for all poles of real parts are less than -2. Thanks for contributing an answer to Stack Overflow! To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Not the answer you're looking for? The string concatenation was not necessary in the first place; you can continue using the stream insertion operator << to perform effective concatenation (instead of using + to form one, temporary std::string object then stream-inserting that one resultant string): And because this is a property of the stream and not the string, you can do it just as well with a char* input: Notice that I added the required const for string literals; you may remove it if and only if your C-strings are not initialised by string literals. char* s; //some code; s = "india"; This is the same as first, the difference is that you are first declaring the pointer, and later assigning it the string literal. Is there a distinction between the diminutive suffices -l and -chen? rev2023.7.7.43526. Why does gravity-induced quantum interference in quantum mechanics show that gravity is not purely geometric at the quantum level? What is the difference between char a[] = ?string? Find centralized, trusted content and collaborate around the technologies you use most. Connect and share knowledge within a single location that is structured and easy to search. Does this group with prime order elements exist? Connect and share knowledge within a single location that is structured and easy to search. Countering the Forcecage spell with reactions? If it where initialized, then in expression *str++ = c; str++ is a post-increment operator, which returns a copy of the pointer whilst incrementing the original. 1. Brute force open problems in graph theory. And how i can add value to it with cin >> p? char a = (*tester)++; does not increase the pointer as you assume; it increases the dereferenced pointer instead, that is, the value a pointer points to. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Similarly, string literals are also an array of characters with an exception that they can not be changed because the compiler may put them read-only data section. If you want to see the pointer value, cast it to void*: (Or you could use one of the C++-specific casts; I'm not sure which is best.). What is this military aircraft I saw near Catalina island? Book or a story about a group of people who had become immortal, and traced it back to a wagon train they had all been on. He wouldn't have it any other way. how can a pointer contain a whole string? If const is no good, then you have little choice but to go with on of the other techniques, But be careful, it's not possible to use any of the string pointers in the question as destination for. What is the reasoning behind the USA criticizing countries and then paying them diplomatic visits? Find centralized, trusted content and collaborate around the technologies you use most. (Ep. Will just the increase in height of water column increase pressure or does mass play any role in it? Is speaking the country's language fluently regarded favorably when applying for a Schengen visa? Space elevator from Earth to Moon with multiple temporary anchors, Number of k-points for unit and super cell. Short story about the best time to travel back to for each season, summer. This operator expects that p points to some memory (automatic,global,dynamic - no matter) - it does not allocate memory by itself. How do they capture these images where the ground and background blend together seamlessly? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. How can I find the following Fourier Transform without directly using FT pairs? What you're trying to do is append something to the string pointed to by the pointer. @FelixPalmen, I realize this (that operator overloading only applies to c++), and that this is a "C" group. }, . ptr[1] is *(ptr + 1) which is a character at the 1st location of string str. It must be the memory address of this char object! ::append - cplusplus.com - The C++ Resources Network sprintf(buffer, "%s%s", chr1,chr2); and is handy for minor issues like tossing in a space between them if you want. The '+' operator adds the two input strings and returns a new string that contains the concatenated string. You cannot assign a string to a char. Invitation to help writing and submitting papers -- how does this scam work? You create a new character array that contains the original array plus the given character. This should work since pointer to the char pointer is passed. Question 3 (2 points) Saved Given the declaration | Chegg.com Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, "using using pointers" is probably referring a pointer to pointer :D, @FelixPalmen, in the case of builtin types this is true, yes, but I like to conceptualize is by explaining it as for non-builtins. Have something appear in the footer only if section isn't over. How to get Romex between two garage doors. I would like to understand how pointers work, so i created this small program. To learn more, see our tips on writing great answers. Draw the initial positions of Mlkky pins in ASCII art, Have something appear in the footer only if section isn't over. Why add an increment/decrement operator when compound assignnments exist? C - Pointer to Pointer (Double Pointer) - GeeksforGeeks (Ep. How to format a JSON string as a table using jq? Use std::string and it will manage all the memory allocation for you: Thanks for contributing an answer to Stack Overflow! Architecture for overriding "trait" implementations many times in different contexts? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Can ultraproducts avoid all "factor structures"? Could you guys please help me with this ? In technically terms I think everything will work fine as long as you do not change the size of the string. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How do I append a single char to a string in C? It is easier. If you know the size of the buffer to which process_name points, you can use strncpy(). The first pointer is used to store the address of the variable. This might not be the best example but it should show the general direction. Now back to your example, comments inline for illustration. How do they capture these images where the ground and background blend together seamlessly? Can we use work equation to derive Ohm's law? ie. Why do keywords have to be reserved words? By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Do you need an "Any" type when implementing a statically typed programming language? What is the Modified Apollo option for a potential LEO transport? Furthermore, you can change up the snippet with pointers (and to give you a better idea of what is happening): Make sure to look up memcpy; and don't forget null terminators (oops). Do United same day changes apply for travel starting on different airlines? Why was the tile on the end of a shower wall jogged over partway up? Characters with only one possible next character. Do you need an "Any" type when implementing a statically typed programming language? Thanks for contributing an answer to Stack Overflow! To learn more, see our tips on writing great answers. yes, it's clear, if i allocate place to p, then it will write "h and some mess" to &q, but if i dont allocate place to p, then it writes "h" only, what is the same as *p. so q=&q? How do they capture these images where the ground and background blend together seamlessly? As pointed out in the comments, you'll need something like char[] as a buffer for the new string. Your final code should looks like below: Note that, you must handle the allocated memory of returned ret somewhere by delete[] it. Initializing an unsigned char: Here we try to insert a char in the unsigned char variable with the help of ASCII value. What is the difference between char a[] = "string"; and char *p = "string"; The Original poster didn't mean to write: Now, adding a single character would seem more efficient than adding a whole string with strcat. Amazon.com : Weber Rapidfire Chimney Starter, Standard, Silver Character Pointer in C - Stack Overflow Therefore any changes to the pointer will be seen outside thereafter. So, How do I do this? It must be the memory address of this char object! Thanks for contributing an answer to Stack Overflow! 15amp 120v adaptor plug for old 6-20 250v receptacle? Number of k-points for unit and super cell, Book or a story about a group of people who had become immortal, and traced it back to a wagon train they had all been on. This means that a string of length 24 needs to be stored in a 25-byte char array. What is the subject in the relative clause that it affects the Earth's balance"? And why can't we copy a string to another but can copy literal strings? Can I change an initialized char pointer via function? Connect and share knowledge within a single location that is structured and easy to search. However, what you're wanting to do is more like C, but since you're in C++, might as well use methods that are part of C++ as much as you can. :), Why on earth are people paying for digital real estate? Please elaborate more on literal string. 587), The Overflow #185: The hardest part of software is requirements, Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned, Testing native, sponsored banner ads on Stack Overflow (starting July 6). First thing to learn and always remember about pointers is to make sure to allocate memory for them, otherwise your program won't run properly. @user2890591 There is an answer containing exact (and correct) use of the entire machinery, look at it :). To learn more, see our tips on writing great answers. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Then here how p is acting like an array itself which is storing a string? How can a char and a char* be appended to an existing string? As has been mentioned earlier a char * basically says "go there" but there is no there there, you never gave it a value. You could pass it by a pointer (to pointer) and change it by dereferrencing it and it's the same with an int - in this case, it doesn't matter if the type is int or char * . What is the difference between char a[] = "string"; and char *p = "string"; Why on earth are people paying for digital real estate? Other than Will Riker and Deanna Troi, have we seen on-screen any commanding officers on starships who are married? alloc an array with the new size and put the old data inside instead, remember that, for a char array, the last value must be \0; calloc() sets all values to \0, which is excellent for char arrays. @Iburidu Back to your example: cout will print out the string "haha" because it will notice you are trying to print a char* if you want to print the address, you may cast it to, yes, on my code i took those first two lines, but its obvious, so i havent put here. Can I contact the editor with relevant personal information in hope to speed-up the review process? Done, application crashed at strcat() string. yes, but in my example p equals to a memory address. Aren't you returning a reference to local variable? You may see inaccurate creative c. Making statements based on opinion; back them up with references or personal experience. rev2023.7.7.43526. 587), The Overflow #185: The hardest part of software is requirements, Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned, Testing native, sponsored banner ads on Stack Overflow (starting July 6). Asking for help, clarification, or responding to other answers. std::string (C++) and char* (or c-string "string" for C) P.S. Characters with only one possible next character. What is the number of ways to spell French word chrysanthme ? But when you do: char *str = "Hello"; char *ptr = str; // ptr points to first character of string str. Find centralized, trusted content and collaborate around the technologies you use most. Proof that deleting all the edges of a cycle in certain connected graph still gives remaining connected graph, My manager warned me about absences on short notice. and i created your example with a[100], and p was "haha", was not equal to a memory address, but it should be! The calloc(int size, sizeof([type])) call alocates all the memory you need to keep your final char*. If i create a pointer, the value of it is a memoryaddress (if i point it to a non-pointer object), but this time it is "haha" in my example. i understand it, but cout << &q must be cout << p then, right? What happens if you do a const_cast on the returned string by c_srt(), then modify the char*, then use c_str() again? Any C textbook or tutorial should explain how to work with strings and pointers. What would a privileged/preferred reference frame look like if it existed? Thanks for contributing an answer to Stack Overflow! To subscribe to this RSS feed, copy and paste this URL into your RSS reader. and i have an char array named second. Making statements based on opinion; back them up with references or personal experience. rev2023.7.7.43526. It resides in implementation defined read only region. How to format a JSON string as a table using jq? Though in C string literals have types of non-const arrays it is better to declare pointers initialized by string literals with qualifier const: If you want to append characters then the code can look the following way (each character of line is appended to buffer in a loop). To learn more, see our tips on writing great answers. So if you indeed need a function that appends a character to a character array I would write it the following way, If you need a function that will contain a copy of the original array plus the given character then it could look the following way. If I am getting it correctly you want to print the base address of the string, the pointer is pointing to. 15amp 120v adaptor plug for old 6-20 250v receptacle? Would it be possible for a civilization to create machines before wheels? A character pointer is again a pointer like the pointers to other types in C. A point to note here is - pointer to a character is different from the pointer to a string. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem, Why on earth are people paying for digital real estate? I was assumming poster wants to add from a position onwards. @ScarletAmaranth, it is never too late to abide by good practices, String literals are const both in C and C++ and omitting the. To learn more, see our tips on writing great answers. @SarpKaya both are blazingly fast (difference would be minimal if any), but I would prefer the "return the pointer" method for readability. Find centralized, trusted content and collaborate around the technologies you use most. What is the subject in the relative clause that it affects the Earth's balance"? How can I append a character to a string? Does this group with prime order elements exist? Due to the ability of a pointer to directly refer to the value that it points to, a pointer has different properties when it points to a char than when it points to an int or a float. Short story about the best time to travel back to for each season, summer, what is meaning of thoroughly in "here is the thoroughly revised and updated, and long-anticipated". The pointer assignment modifies the pointer and keeps the previously pointed characters unmodified, while assigning to the pointed character modifies the pointed characters, while keeping the pointer unmodified. Experts I've some doubts in this programme. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. This will trigger a warning of local variables if you do not hardcode the return value as a string literal. Select Add Text Captions. to dynamically allocate memory. Parameters str 587), The Overflow #185: The hardest part of software is requirements, Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned, Testing native, sponsored banner ads on Stack Overflow (starting July 6), Trying to reason with an undefined behavior of char pointer initialized to string literals, Trouble with char* and char** (C --> C++), Problem dereferencing char pointer in C++, Incompatible types in assignment char ** to char *, pointer to char array, unhandled exception. For cout << &q - operator << (ostream&, char* p) expects that p points to NULL terminated string - and &q points to memory containing "H" but what is after this character no one knows - so you will get some garbage on screen. Brute force open problems in graph theory. You are actually trying to make changes to a string literal, which may resides in the read-only memory, causing undefined behaviour. Number of k-points for unit and super cell. How did the IBM 360 detect memory errors? Asking for help, clarification, or responding to other answers. To learn more, see our tips on writing great answers. c - append a character from an array to a char pointer - Stack Overflow Don't mess your head with pointers and try: The same with your pointer. Yes, the original may be evaluated, but the "copy" is returned, as it amounts to an lvalue, Why on earth are people paying for digital real estate? Not the answer you're looking for? Not just printing, I need to get char * variable as result container, which I need for futherer usage. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Wherever in the program, we use str, this will give the base address of string "Hello". How did the IBM 360 detect memory errors? what is meaning of thoroughly in "here is the thoroughly revised and updated, and long-anticipated".

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