strncat - Online Linux Manual PageSection : 3
Updated : 2023-02-05
Source : Linux man-pages 6.03

---

NAMEstrncat − concatenate a null-padded character sequence into a string

---

LIBRARYStandard C library (libc, −lc)

---

SYNOPSIS#include <string.h>char *strncat(char *restrict dst, const char src[restrict .sz], size_t sz);

---

DESCRIPTIONThis function catenates the input character sequence contained in a null-padded fixed-width buffer, into a string at the buffer pointed to by dst. The programmer is responsible for allocating a destination buffer large enough, that is, strlen(dst) + strnlen(src, sz) + 1. An implementation of this function might be: char * strncat(char *restrict dst, const char *restrict src, size_t sz) { int len; char *p; len = strnlen(src, sz); p = dst + strlen(dst); p = mempcpy(p, src, len); *p = '\0'; return dst; }

---

RETURN VALUEstrncat() returns dst.

---

ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7). InterfaceAttributeValue strncat() Thread safetyMT-Safe

---

STANDARDSPOSIX.1-2001, POSIX.1-2008, C99, SVr4, 4.3BSD.

---

CAVEATSThe name of this function is confusing. This function has no relation to strncpy(3). If the destination buffer is not large enough, the behavior is undefined. See _FORTIFY_SOURCE in feature_test_macros(7).

---

BUGSThis function can be very inefficient. Read about Shlemiel the painter .

---

EXAMPLES #include <err.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #define nitems(arr) (sizeof((arr)) / sizeof((arr)[0])) int main(void) { size_t maxsize; // Null-padded fixed-width character sequences char pre[4] = "pre."; char new_post[50] = ".foo.bar"; // Strings char post[] = ".post"; char src[] = "some_long_body.post"; char *dest; maxsize = nitems(pre) + strlen(src) − strlen(post) + nitems(new_post) + 1; dest = malloc(sizeof(*dest) * maxsize); if (dest == NULL) err(EXIT_FAILURE, "malloc()"); dest[0] = '\0'; // There's no 'cpy' function to this 'cat'. strncat(dest, pre, nitems(pre)); strncat(dest, src, strlen(src) − strlen(post)); strncat(dest, new_post, nitems(new_post)); puts(dest); // "pre.some_long_body.foo.bar" free(dest); exit(EXIT_SUCCESS); }

---

SEE ALSOstring(3), string_copying(3) 0

---

Johanes Gumabo

---

Data Size   :   10,996 byte
man-strncat.3Build   :   2024-12-05, 20:55   :  
Visitor Screen   :   x
Visitor Counter ( page / site )   :   4 / 239,085
Visitor ID   :     :  
Visitor IP   :   3.142.195.79   :  
Visitor Provider   :   AMAZON-02   :  
Provider Position ( lat x lon )   :   39.962500 x -83.006100   :   x
Provider Accuracy Radius ( km )   :   1000   :  
Provider City   :   Columbus   :  
Provider Province   :   Ohio ,   :   ,
Provider Country   :   United States   :  
Provider Continent   :   North America   :  
Visitor Recorder   :   Version   :  
Visitor Recorder   :   Library   :  
Online Linux Manual Page   :   Version   :   Online Linux Manual Page - Fedora.40 - march=x86-64 - mtune=generic - 24.12.05
Online Linux Manual Page   :   Library   :   lib_c - 24.10.03 - march=x86-64 - mtune=generic - Fedora.40
Online Linux Manual Page   :   Library   :   lib_m - 24.10.03 - march=x86-64 - mtune=generic - Fedora.40
Data Base   :   Version   :   Online Linux Manual Page Database - 24.04.13 - march=x86-64 - mtune=generic - fedora-38
Data Base   :   Library   :   lib_c - 23.02.07 - march=x86-64 - mtune=generic - fedora.36

---

Very long time ago, I have the best tutor, Wenzel Svojanovsky . If someone knows the email address of Wenzel Svojanovsky , please send an email to johanes_gumabo@yahoo.co.id .

---

If error, please print screen and send to johanes_gumabo@yahoo.co.id
Under development. Support me via PayPal.

---