Shulou(Shulou.com)06/01 Report--

Most people do not understand the knowledge points of this article "how to use strcpy functions in C language", so the editor summarizes the following, detailed content, clear steps, and has a certain reference value. I hope you can get something after reading this article. Let's take a look at this "how to use strcpy functions in C language" article.

The string functions in C language are as follows

Get string length

Strlen

String function with unlimited length

Strcpy

Strcat

Strcmp

String function with limited length

Strncpy

Strncat

Strncmp

String lookup

Strstr

Strtok

Error message report

Strerror

Let's see how to implement them.

String function strcpy with unlimited length

Let's see what the document says, as follows

Strcpy document

Char * strcpy (char * destination, const char * source)

Copy string

String copy (string copy)

Copies the C string pointed by source into the array pointed by destination, including the terminating null character (and stopping at that point).

Copy the C string pointed by the character pointer source to another character array, which is pointed to by the character pointer destination

To avoid overflows, the size of the array pointed by destination shall be long enough to contain the same C string as source (including the terminating null character), and should not overlap in memory with source.

To avoid overflow, the character array pointed to by destination needs to be long enough to contain the source string (including'\ 0')

To sum up, we can know

The'\ 0' in the source string is copied to the destination space, and the source string must end with'\ 0'.

The target space must be large enough to ensure that the source string can be stored.

How to make a copy? Int main () {char arr1 [] = "abcdefghi"; char arr2 [] = "bit"; / / copy the contents of arr2 to arr1 / / strcpy (arr1, arr2); / / how to copy? My_strcpy (arr1, arr2); printf ("% s\ n", arr1); return 0;} implementation

It is a good habit to assert that the pointer is not empty.

/ / char* my_strcpy (char* dest, char* src) / / src plus const, why? Because we only need to copy and do not need to change the source string to prevent modification, we add const to modify char* my_strcpy (char* dest, const char* src) {assert (dest! = NULL); assert (src! = NULL); while (* src! ='\ 0') {* dest = * src; dest++; src++ } * dest = * src; / /'\ 0' / / returns the starting address of the destination space return dest;}

Copy the source string to the destination space, look for'\ 0', execute * dest = * src if it is not'\ 0', assign the source character to the destination space, and then both pointers are offset back, that is, both are + +. When * src is'\ 0', indicating that the source string has reached the end, exit the loop, directly assign'\ 0' to * dest, and finally return dest

Can be optimized as follows

Char* my_strcpy (char* dest, const char* src) {assert (dest! = NULL); assert (src! = NULL); / / optimize while (* src! ='\ 0') {* dest++ = * src++;} * dest = * src; / /'\ 0' / return the starting address of the destination space return dest;}

Of course, you can continue to optimize and become more concise, directly using * dest++ = * src++ as the judgment condition, while performing the operation, as follows

Char* my_strcpy (char* dest, const char* src) {assert (dest! = NULL); assert (src! = NULL); / / optimize / / copy the string pointed to by src to the space pointed to by dest, including'\ 0' char* rest = dest; while (* dest++ = * src++) { } / return the starting address of the destination space return rest;} the above is about the article "how to use strcpy function in C language". I believe you all have some understanding. I hope the content shared by the editor will be helpful to you. If you want to know more about it, please follow the industry information channel.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.