convert string to char

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Possible Duplicate    Convert std  string to const char  or char        Probably a  amp  or something similar missing  I am noob at cpp    I have   string R    somthing   char   S    How would I copy R into S

User · Answer

First of all  you would have to allocate memory   char   S   new char R length     1     then you can use strcpy with S and R c str     std  strcpy S R c str       You can also use R c str   if the string doesn t get changed or the c string is only used once  However  if S is going to be modified  you should copy the string  as writing to R c str   results in undefined behavior   Note  Instead of strcpy you can also use str  copy

User · Answer

There are many ways  Here are at least five         An example of converting std  string to  const char  using five    different methods  Error checking is emitted for simplicity        Compile and run example  using gcc on Unix-like systems            g   -Wall -pedantic -o test   test cpp         test     Original string  0x7fe3294039f8   hello     s1  0x7fe3294039f8   hello     s2  0x7fff5dce3a10   hello     s3  0x7fe3294000e0   hello     s4  0x7fe329403a00   hello     s5  0x7fe329403a10   hello       include  lt alloca h gt   include  lt string gt   include  lt cstring gt   int main         std  string s0      const char  s1      char  s2      char  s3      char  s4      char  s5          This is the initial C   string      s0    hello           Method  1  Just use  c str    method to obtain a pointer to a        null-terminated C string stored in std  string object         Be careful though because when  s0  goes out of scope  s1 points        to a non-valid memory      s1   s0 c str            Method  2  Allocate memory on stack and copy the contents of the        original string  Keep in mind that once a current function returns         the memory is invalidated      s2    char   alloca s0 size     1       memcpy s2  s0 c str    s0 size     1           Method  3  Allocate memory dynamically and copy the content of the        original string  The memory will be valid until you explicitly        release it using  free   Forgetting to release it results in memory        leak      s3    char   malloc s0 size     1       memcpy s3  s0 c str    s0 size     1           Method  4  Same as method  3  but using C   new delete operators      s4   new char s0 size     1       memcpy s4  s0 c str    s0 size     1           Method  5  Same as 3 but a bit less efficient       s5   strdup s0 c str             Print those strings      printf  Original string   p    s n   s0 c str    s0 c str         printf  s1   p    s n   s1  s1       printf  s2   p    s n   s2  s2       printf  s3   p    s n   s3  s3       printf  s4   p    s n   s4  s4       printf  s5   p    s n   s5  s5           Release memory        free s3       delete    s4      free s5

[c++] convert string to char*

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