How to concatenate two strings in C

Question

I have a private class variable char name 10  to which I would like to add the  txt extension so that I can open the file present in the directory    How do I go about this   It would be preferable to create a new string variable that holds the concatenated string

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If you were programming in C  then assuming name really is a fixed-length array like you say  you have to do something like the following   char filename sizeof name    4   strcpy  filename  name    strcat  filename    txt     FILE  fp   fopen  filename       You see now why everybody recommends std  string

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strcat destination source  can be used to concatenate two strings in c     To have a deep understanding you can lookup in the following link-  http   www cplusplus com reference cstring strcat

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C  14  std  string great    Hello s     World      concatenation easy    Answer on the question   auto fname     s   name     txt

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First of all  don t use char  or char N   Use std  string  then everything else becomes so easy   Examples   std  string s    Hello   std  string greet   s     World     concatenation easy    Easy  isn t it    Now if you need char const   for some reason  such as when you want to pass to some function  then you can do this   some c api s c str    s size        assuming this function is declared as   some c api char const  input  size t length     Explore std  string yourself starting from here    Documentation of std  string   Hope that helps

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String appending  include  lt iostream gt  using namespace std   void stringconcat char  str1  char  str2       while   str1      0            str1               while  str2      0             str1    str2          str1            str2             int main         char str1 100       cin getline str1  100         char str2 100       cin getline str2  100        stringconcat str1  str2        cout lt  lt str1      getchar        return 0

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It is better to use C   string class instead of old style C string  life would be much easier    if you have existing old style string  you can covert to string class      char greeting 6      H    e    l    l    o     0        cout lt  lt greeting    and there  n     will not compile because concat does  n not work on old C style string     string trueString   string  greeting       cout  lt  lt  trueString    and there  n      compiles fine     cout  lt  lt  trueString    c      this will be fine too  if one of the operand if C   string  this will work too

User · Answer

Since it s C   why not to use std  string instead of char   Concatenation will be trivial   std  string str    abc   str     another

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There is a strcat   function from the ported C library that will do  C style string  concatenation for you   BTW even though C   has a bunch of functions to deal with C-style strings  it could be beneficial for you do try and come up with your own function that does that  something like   char   con const char   first  const char   second        int l1   0  l2   0      const char   f   first    l   second          step 1 - find lengths  you can also use strlen      while   f      l1      while   l      l2       char  result   new char l1   l2           then concatenate     for  int i   0  i  lt  l1  i    result i    first i       for  int i   l1  i  lt  l1   l2  i    result i    second i - l1           finally   cap  result with terminating null char     result l1 l2      0       return result         and then     char s1      file name   char  c   con s1    txt          the result of which is file name txt   You might also be tempted to write your own operator   however IIRC operator overloads with only pointers as arguments is not allowed   Also  don t forget the result in this case is dynamically allocated  so you might want to call delete on it to avoid memory leaks  or you could modify the function to use stack allocated character array  provided of course it has sufficient length

[c++] How to concatenate two strings in C++?

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