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Q&A How can I manage multiple consecutive strings in a buffer (and add more later)?

This question is inspired by If I have a char array containing strings with a null byte (\0) terminating each string, how would I add another string onto the end? on Stack Overflow. Suppose I have...

2 answers  ·  posted 9mo ago by Karl Knechtel‭  ·  last activity 8mo ago by Lundin‭

Question c string
#2: Post edited by user avatar Karl Knechtel‭ · 2024-03-21T19:42:29Z (9 months ago)
  • *This question is inspired by [If I have a char array containing strings with a null byte (\0) terminating each string, how would I add another string onto the end?](https://stackoverflow.com/questions/78202169) on Stack Overflow*.
  • Suppose I have a `char[]` buffer that I'm using to represent multiple null-terminated (ASCII) strings, one after the other. I can easily set up an initial state that has two strings and sufficient room to add a third:
  • ```
  • char buffer[20] = {'o', 'n', 'e', '\0', 't', 'w', 'o', '\0'};
  • ```
  • Now suppose I have `char* another_string = "three";`. How can I append or concatenate it to the buffer, generally? I do not want to concatenate the `three` with the `two`, but instead put it in the buffer as a separate string.
  • I already know that the `str` library functions expect a string to be null-terminated, so they won't help here. For example, `strcat` would find the first null in the array instead of the second, and overwrite it; and `strncpy` would need a pointer to where to start writing.
  • *This question is inspired by [If I have a char array containing strings with a null byte (\0) terminating each string, how would I add another string onto the end?](https://stackoverflow.com/questions/78202169) on Stack Overflow*.
  • Suppose I have a `char[]` buffer that I'm using to represent multiple null-terminated (ASCII) strings, one after the other. I can easily set up an initial state that has two strings and sufficient room to add a third:
  • ```
  • /* The exact amount of space is not critical to the question; it's enough
  • to store these strings and leave room for more. */
  • char buffer[80] = {'o', 'n', 'e', '\0', 't', 'w', 'o', '\0'};
  • ```
  • Now suppose I have `char* another_string = "three";`. How can I append or concatenate `another_string` to the `buffer`, generally? I do not want to concatenate the `three` text with the `two`, but instead put it in the buffer as a separate string.
  • I already know that the `<string.h>` library functions expect a string to be null-terminated, so it seems like they won't help here. For example, `strcat` would find the first null in the array instead of the second, and overwrite it; and `strncpy` would need a pointer to where to start writing.
#1: Initial revision by user avatar Karl Knechtel‭ · 2024-03-21T19:15:40Z (9 months ago)
How can I manage multiple consecutive strings in a buffer (and add more later)?
*This question is inspired by [If I have a char array containing strings with a null byte (\0) terminating each string, how would I add another string onto the end?](https://stackoverflow.com/questions/78202169) on Stack Overflow*.

Suppose I have a `char[]` buffer that I'm using to represent multiple null-terminated (ASCII) strings, one after the other. I can easily set up an initial state that has two strings and sufficient room to add a third:

```
char buffer[20] = {'o', 'n', 'e', '\0', 't', 'w', 'o', '\0'};
```

Now suppose I have `char* another_string = "three";`. How can I append or concatenate it to the buffer, generally? I do not want to concatenate the `three` with the `two`, but instead put it in the buffer as a separate string.

I already know that the `str` library functions expect a string to be null-terminated, so they won't help here. For example, `strcat` would find the first null in the array instead of the second, and overwrite it; and `strncpy` would need a pointer to where to start writing.