Difference between revisions of "c/string/byte/strncpy"
From cppreference.com
(Example showing: - →no buffer overflow: has buffer overflow. Fixed with: >> sizeof( copy )-1 <<) |
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| Line 39: | Line 39: | ||
{ | { | ||
char str[] = "Hello, world!"; | char str[] = "Hello, world!"; | ||
| − | char copy[40]; | + | char copy[40] = { 0 }; |
/* no buffer overflow */ | /* no buffer overflow */ | ||
Revision as of 03:56, 2 May 2014
| Defined in header <string.h>
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| char *strncpy( char *dest, const char *src, size_t count ); |
(until C99) | |
| char *strncpy( char *restrict dest, const char *restrict src, size_t count ); |
(since C99) | |
Copies at most count characters of the byte string pointed to by src (including the terminating null character) to character array pointed to by dest.
If count is reached before the entire string src was copied, the resulting character array is not null-terminated.
If, after copying the terminating null character from src, count is not reached, additional null characters are written to dest until the total of count characters have been written.
If the strings overlap, the behavior is undefined.
Contents |
Parameters
| dest | - | pointer to the character array to copy to |
| src | - | pointer to the byte string to copy from |
| count | - | maximum number of characters to copy |
Return value
dest
Example
Run this code
#include <stdio.h> #include <string.h> int main(void) { char str[] = "Hello, world!"; char copy[40] = { 0 }; /* no buffer overflow */ strncpy(copy, str, sizeof(copy)-1); printf("%s\n", copy); /* copy partial amount of data */ strncpy(copy, str, 5); /* add manually nullbyte. * comment it to see difference */ copy[5] = '\0'; printf("%s\n", copy); return 0; }
Output:
Hello, world! Hello
See also
| (C11) |
copies one string to another (function) |
| (C11) |
copies one buffer to another (function) |
| C++ documentation for strncpy
| |
