GSP
Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Support
Contact Us
Online Help
Handbooks
Domain Status
Man Pages

FAQ
Virtual Servers
Pricing
Billing
Technical

Network
Facilities
Connectivity
Topology Map

Miscellaneous
Server Agreement
Year 2038
Credits
 

USA Flag

 

 

Man Pages


Manual Reference Pages  -  STRNCAT (3)

NAME

strcat, strncat - concatenate strings

CONTENTS

Library
Synopsis
Description
Return Values
See Also
Standards
Security Considerations

LIBRARY


.Lb libc

SYNOPSIS


.In string.h char * strcat char * restrict s const char * restrict append char * strncat char * restrict s const char * restrict append size_t count

DESCRIPTION

The strcat and strncat functions append a copy of the null-terminated string append to the end of the null-terminated string s, then add a terminating \0’. The string s must have sufficient space to hold the result.

The strncat function appends not more than count characters from append, and then adds a terminating \0’.

RETURN VALUES

The strcat and strncat functions return the pointer s.

SEE ALSO

bcopy(3), memccpy(3), memcpy(3), memmove(3), strcpy(3), strlcat(3), strlcpy(3), wcscat(3)

STANDARDS

The strcat and strncat functions conform to -isoC.

SECURITY CONSIDERATIONS

The strcat function is easily misused in a manner which enables malicious users to arbitrarily change a running program’s functionality through a buffer overflow attack.

Avoid using strcat. Instead, use strncat or strlcat and ensure that no more characters are copied to the destination buffer than it can hold.

Note that strncat can also be problematic. It may be a security concern for a string to be truncated at all. Since the truncated string will not be as long as the original, it may refer to a completely different resource and usage of the truncated resource could result in very incorrect behavior. Example:

void
foo(const char *arbitrary_string)
{
        char onstack[8];

#if defined(BAD)         /*          * This first strcat is bad behavior. Do not use strcat!          */         (void)strcat(onstack, arbitrary_string);        /* BAD! */ #elif defined(BETTER)         /*          * The following two lines demonstrate better use of          * strncat().          */         (void)strncat(onstack, arbitrary_string,          sizeof(onstack) - strlen(onstack) - 1); #elif defined(BEST)         /*          * These lines are even more robust due to testing for          * truncation.          */         if (strlen(arbitrary_string) + 1 >          sizeof(onstack) - strlen(onstack))                 err(1, "onstack would be truncated");         (void)strncat(onstack, arbitrary_string,          sizeof(onstack) - strlen(onstack) - 1); #endif }

Search for    or go to Top of page |  Section 3 |  Main Index


Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.