cpp std

snprintf

snprintf is a function that formats a string and writes the resulting characters to a character array.

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int snprintf(char *str, size_t size, const char *format, ...);
  • str: A pointer to the destination buffer where the resulting string is stored.
  • size: The size of the destination buffer (including the null-terminating character).
  • format: A format string that specifies the desired format of the output.
  • ...: Additional arguments corresponding to the placeholders in the format string.
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    int main() {
        size_t n = std::snprintf(nullptr, 0, "%s", "hello, world");
        std::cout << n << std::endl;  // print 12
        return 0;
    }

string

std::string(n, '\0')

creates a string with a length of n and fills it with null characters (‘\0’).

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size_t n = 10;
std::string myString(n, '\0');

strerror_r

is a function that is commonly used for thread-safe retrieval of error messages. The purpose of this function is to convert an error number (an integer typically set by a system call or library function to indicate an error) into a human-readable error message

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#include <cstring>

int strerror_r(int errnum, char *buf, size_t buflen);
  • errnum: The error number for which you want to retrieve the error message.
  • buf: A pointer to the buffer where the error message will be stored.
  • buflen: The size of the buffer pointed to by buf.

others

  • strncpy: Copy no more than N characters of SRC to DEST.
  • std::strlen: Return the length of String.
  • std::strstr is a standard C library function that is used to find the first occurrence of a substring within a string. The function returns a pointer to the first occurrence of the substring in the given string, or NULL if the substring is not found.