What does strdup () do in C?
Table of Contents
What does strdup () do in C?
The function strdup() is used to duplicate a string. It returns a pointer to null-terminated byte string.
How is strdup implemented?
Now, strdup() uses malloc() under the hood to automatically allocate the memory for you. However, this means that you must free the memory yourself, after you finish using it! So, simply put, strdup() allocates memory using malloc() , and then copies your source string to the allocated memory.
What does strdup return?
The strdup() function returns a pointer to a new string which is a duplicate of the string s. Memory for the new string is obtained with malloc(3), and can be freed with free(3). The strndup() function is similar, but copies at most n bytes.
Is strdup a standard?
Most C programmers are familiar with the strdup function. Many of them will take it for granted, yet it is not part of the C Standard (neither C89, C99 nor C11). It is part of POSIX and may not be available on all environments. Indeed Microsoft insisted on renaming it _strdup , adding to confusion.
Why do we need strdup?
The strdup() and strndup() functions are used to duplicate a string. strdup() : Syntax : char *strdup(const char *s); This function returns a pointer to a null-terminated byte string, which is a duplicate of the string pointed to by s.
Do I have to free strdup?
Because also strdup() allocates memory then it must be freed (see doc). strdup is a malloc in disguise. Reading the documentation of a standard function is faster than asking on SO ! strdup is not a Standard C function, however it is in POSIX.
What is the difference between strcpy and strdup?
strdup allocates memory for the new string on the heap, while using strcpy (or its safer strncpy varient) I can copy a string to a pre allocated memory on either the heap or the stack.
Does strdup call malloc?
Use the strdup Function to Duplicate the Given String in C It implements string copying functionality but does memory allocation and checking internally. Although a user is responsible for freeing the returned char pointer since the strdup allocates the memory with malloc function call.
Is strdup deprecated?
warning C4996: ‘strdup’: The POSIX name for this item is deprecated.
Can strdup return null?
The strdup() function shall return a pointer to a new string on success. Otherwise, it shall return a null pointer and set errno to indicate the error.
What is the difference between Strcpy and strdup?
What is the difference between strdup and Strcpy?
Does strdup allocate memory?
The strdup() function allocates sufficient memory for a copy of the string str , does the copy, and returns a pointer to it.
Can strdup fail?
The strdup () and strndup () functions may fail and set the external variable errno for any of the errors specified for the library function malloc(3).
Is Memmove faster than memcpy?
“memcpy is more efficient than memmove.” In your case, you most probably are not doing the exact same thing while you run the two functions. In general, USE memmove only if you have to.
What is strdup and strndup in C++?
strdup() and strndup() functions in C/C++. The strdup() and strndup() functions are used to duplicate a string. strdup() : Syntax : char *strdup(const char *s); This function returns a pointer to a null-terminated byte string, which is a duplicate of the string pointed to by s.
Should I write my own strdup function?
If you must implement your own strdup function, at least rely on the rest of string.h for as much as you can. Many of these functions are optimized, and faster than you can write them yourself.
How does the function strndup () work?
The function strndup works similar to the function strndup (). This function duplicates the string at most size bytes i.e. the given size in the function. It also returns a pointer to null-terminated byte string.
Why does strdup return null after changing a string?
It tries to allocate enough memory to hold the old string (plus a ‘\\0’ character to mark the end of the string). If the allocation failed, it sets errno to ENOMEM and returns NULL immediately. Setting of errno to ENOMEM is something malloc does in POSIX so we don’t need to explicitly do it in our strdup.
