strlcpy(3)                 Library Functions Manual                 strlcpy(3)

NAME
       strlcpy, strlcat - string return-hypothetical-non-truncated-length
       copy/catenate (with truncation)

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #include <string.h>

       size_t strlcpy(size_t dsize;
                      char dst[restrict dsize], const char *restrict src,
                      size_t dsize);
       size_t strlcat(size_t dsize;
                      char dst[restrict dsize], const char *restrict src,
                      size_t dsize);

DESCRIPTION
       strlcpy() copies the string pointed to by src, into a string at the
       buffer pointed to by dst.

       strlcat() catenates the string pointed to by src, after the string
       pointed to by dst (overwriting its terminating null byte).

       For both functions, if the string doesn't fit in the buffer, it is
       truncated.

RETURN VALUE
       These functions return the total length of the string they tried to
       create, as if truncation didn't happen.

STANDARDS
       POSIX.1-2024.

HISTORY
       OpenBSD 2.4, POSIX.1-2024, glibc 2.38.

BUGS
       These functions are vulnerable to denial of service (DoS) attacks,
       since they read the entire source string.

       strscpy(9) is a better function for copying with truncation, as it
       doesn't have that issue.  It's not provided by libc, so users should
       write their own implementation.

SEE ALSO
       strlcpy(3), strcpy(3), string(3)

Linux man-pages 6.19              2026-07-11                        strlcpy(3)