diff options
Diffstat (limited to 'man3/strncat.3')
| -rw-r--r-- | man3/strncat.3 | 67 |
1 files changed, 34 insertions, 33 deletions
diff --git a/man3/strncat.3 b/man3/strncat.3 index f53c930..74848c9 100644 --- a/man3/strncat.3 +++ b/man3/strncat.3 @@ -3,43 +3,45 @@ .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" -.TH strncat 3 2023-07-20 "Linux man-pages 6.05.01" +.TH strncat 3 2023-12-05 "Linux man-pages 6.7" .SH NAME -strncat \- concatenate a null-padded character sequence into a string +strncat +\- +append non-null bytes from a source array to a string, +and null-terminate the result .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .B #include <string.h> -.PP -.BI "char *strncat(char *restrict " dst ", const char " src "[restrict ." sz ], -.BI " size_t " sz ); +.P +.BI "char *strncat(char *restrict " dst ", const char " src "[restrict ." ssize ], +.BI " size_t " ssize ); .fi .SH DESCRIPTION -This function catenates the input character sequence -contained in a null-padded fixed-width buffer, -into a string at the buffer pointed to by +This function appends at most +.I ssize +non-null bytes from the array pointed to by +.IR src , +followed by a null character, +to the end of the string pointed to by .IR dst . -The programmer is responsible for allocating a destination buffer large enough, -that is, -.IR "strlen(dst) + strnlen(src, sz) + 1" . -.PP +.I dst +must point to a string contained in a buffer that is large enough, +that is, the buffer size must be at least +.IR "strlen(dst) + strnlen(src, ssize) + 1" . +.P An implementation of this function might be: -.PP +.P .in +4n .EX char * -strncat(char *restrict dst, const char *restrict src, size_t sz) +strncat(char *restrict dst, const char *restrict src, size_t ssize) { - int len; - char *p; -\& - len = strnlen(src, sz); - p = dst + strlen(dst); - p = mempcpy(p, src, len); - *p = \[aq]\e0\[aq]; + #define strnul(s) (s + strlen(s)) \& + stpcpy(mempcpy(strnul(dst), src, strnlen(src, ssize)), ""); return dst; } .EE @@ -62,17 +64,17 @@ T{ .BR strncat () T} Thread safety MT-Safe .TE -.sp 1 .SH STANDARDS C11, POSIX.1-2008. .SH HISTORY POSIX.1-2001, C89, SVr4, 4.3BSD. .SH CAVEATS -The name of this function is confusing. -This function has no relation to +The name of this function is confusing; +it has no relation to .BR strncpy (3). -.PP -If the destination buffer is not large enough, +.P +If the destination buffer does not already contain a string, +or is not large enough, the behavior is undefined. See .B _FORTIFY_SOURCE @@ -82,7 +84,7 @@ in This function can be very inefficient. Read about .UR https://www.joelonsoftware.com/\:2001/12/11/\:back\-to\-basics/ -Shlemiel the painter +Shlemiel the painter .UE . .SH EXAMPLES .\" SRC BEGIN (strncat.c) @@ -97,9 +99,9 @@ Shlemiel the painter int main(void) { - size_t maxsize; + size_t n; \& - // Null-padded fixed-width character sequences + // Null-padded fixed-size character sequences char pre[4] = "pre."; char new_post[50] = ".foo.bar"; \& @@ -108,9 +110,8 @@ main(void) char src[] = "some_long_body.post"; char *dest; \& - maxsize = nitems(pre) + strlen(src) \- strlen(post) + - nitems(new_post) + 1; - dest = malloc(sizeof(*dest) * maxsize); + n = nitems(pre) + strlen(src) \- strlen(post) + nitems(new_post) + 1; + dest = malloc(sizeof(*dest) * n); if (dest == NULL) err(EXIT_FAILURE, "malloc()"); \& @@ -128,4 +129,4 @@ main(void) .in .SH SEE ALSO .BR string (3), -.BR string_copying (3) +.BR string_copying (7) |