C - String String Concatenating

Introduction

Concatenation is to append one string to the end of another.

strcat_s() function in string.h does the string concatenating.

strcat_s() requires three arguments:

the address of the string that is to be appended to,
the maximum length of the string that can be stored by the first argument, and
the address of the string that is to be appended to the first argument.

The function returns an integer error code as a value of type errno_t, which is an integer type that is compiler dependent.

char str1[50] = "To be, or not to be, ";
char str2[] = "that is the question.";
int retval = strcat_s(str1, sizeof(str1), str2);
if(retval)
  printf("There was an error joining the strings. Error code = %d",retval);
else
  printf("The combined strings:\n%s\n", str1);

The code above uses strcat_s() to append str2 to str1.

The operation copies str2 to the end of str1, overwriting the \0 in str1, then appending a final \0.

When everything works as it should, strcat_s() returns 0.

If str1 is not large enough or there is some other error, the return value will be nonzero.

strncat_s() concatenates part of one string to another.

This has an extra argument specifying the maximum number of characters to be concatenated. Here's how that works:

char str1[50] = "To be, or not to be, ";
char str2[] = "that is the question.";
int retval = strncat_s(str1, sizeof(str1), str2, 4);
if(retval)
  printf("There was an error joining the strings. Error code = %d",retval);
else
  printf("The combined strings:\n%s\n", str1);

C - String String Concatenating

Introduction

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