| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | NOTES | SEE ALSO | COLOPHON | The Linux Programming Interface |
STRCAT(3) Linux Programmer's Manual STRCAT(3)
strcat, strncat - concatenate two strings
#include <string.h>
char *strcat(char *dest, const char *src);
char *strncat(char *dest, const char *src, size_t n);
The strcat() function appends the src string to the dest string,
overwriting the terminating null byte ('\0') at the end of dest, and
then adds a terminating null byte. The strings may not overlap, and
the dest string must have enough space for the result. If dest is
not large enough, program behavior is unpredictable; buffer overruns
are a favorite avenue for attacking secure programs.
The strncat() function is similar, except that
* it will use at most n bytes from src; and
* src does not need to be null-terminated if it contains n or more
bytes.
As with strcat(), the resulting string in dest is always null-
terminated.
If src contains n or more bytes, strncat() writes n+1 bytes to dest
(n from src plus the terminating null byte). Therefore, the size of
dest must be at least strlen(dest)+n+1.
A simple implementation of strncat() might be:
char*
strncat(char *dest, const char *src, size_t n)
{
size_t dest_len = strlen(dest);
size_t i;
for (i = 0 ; i < n && src[i] != '\0' ; i++)
dest[dest_len + i] = src[i];
dest[dest_len + i] = '\0';
return dest;
}
The strcat() and strncat() functions return a pointer to the
resulting string dest.
SVr4, 4.3BSD, C89, C99.
Some systems (the BSDs, Solaris, and others) provide the following
function:
size_t strlcat(char *dest, const char *src, size_t size);
This function appends the null-terminated string src to the string
dest, copying at most size-strlen(dest)-1 from src, and adds a null
terminator to the result, unless size is less than strlen(dest).
This function fixes the buffer overrun problem of strcat(), but the
caller must still handle the possibility of data loss if size is too
small. The function returns the length of the string strlcat() tried
to create; if the return value is greater than or equal to size, data
loss occurred. If data loss matters, the caller must either check
the arguments before the call, or test the function return value.
strlcat() is not present in glibc and is not standardized by POSIX,
but is available on Linux via the libbsd library.
bcopy(3), memccpy(3), memcpy(3), strcpy(3), string(3), strncpy(3),
wcscat(3), wcsncat(3)
This page is part of release 3.51 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
GNU 2012-07-19 STRCAT(3)
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