473,898 Members | 3,971 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

what is the difference between sprintf and snprintf?

72 New Member
Hi All,

I wants to know what is the difference between sprintf and snprintf?

Jul 28 '09 #1
11 44919
11,448 Recognized Expert MVP
Have you read the documentation for both functions? sprintf() is part of the Standard Library while snprintf() isn't. The second function limits the number of characters written to the output character buffer while the first one doesn't. The first function can cause buffer overflow while the second function can protect you from that (if used correctly).

kind regards,

Jul 28 '09 #2
72 New Member
Hi JosAH,

Thanks for your reply...

I didnt understand how the snprintf protect from buffer flow, Can you explain bit elaborative?

Jul 28 '09 #3
11,448 Recognized Expert MVP

You can tell the snprintf() function to print at most n characters, no matter any buffer size or the size of the complete output; if you set n+1 equal to the size of your buffer the buffer will never overflow (n+1 because that function prints a terminating \0).

kind regards,

Jul 28 '09 #4
9,065 Recognized Expert Moderator Expert
In most snprintf implementation I have seen/seen documented the size passed to the function is the buffer size. So if you have a buffer of N bytes you pass N as the size to the snprint and it writes at most N-1 characters to the buffer followed by a zero terminator.
Jul 28 '09 #5
11,448 Recognized Expert MVP
Have a look at this link, I think that's one of the reasons it isn't part of the Standard yet.

kind regards,

Jul 28 '09 #6
1 New Member
A Buffer Overflow is caused by writing data over the border of reserved memory space for something.
Which could cause all kind of errors and unwanted behaviours.
With sprintf you can't control how much characters(byte s) are being written into a reserved memory space.

the last character is always a "\0" escape sequence with sprintf and snprintf. So for a string of 4 characters like "abcd" I would need to reserve 5 chars(bytes) with something like "char strBuffer[5]".

char strBuffer[5];
sprintf(strBuff er, "123456");

I reserve 5 bytes(chars) for the char buffer but try to write a string into it that's 6 bytes(chars)+1( for "\0") long. In other words I'm overflowing the the char buffer by 2 bytes(chars) which is being written into unknown memory area like described above.

With snprintf I can control how many characters(byte s) are written into the char buffer at max(which should be the number of reserved chars(bytes) for the char buffer) to avoid any overflow of data over the area of reserved memory.

char strBuffer[5];
sprintf(strBuff er, sizeof(strBuffe r), "123456");

The expected result would be "1234" because the last and 5th character must be the "\0" escape sequence so it's actually "1234\0"
But u can't see the escape sequence, it's only for the program to know where the string ends.

I hope this helped everyone.
Here is an example:
Jun 28 '21 #7
2 New Member
(1) String buffer of sprintf and snprintf functions
Because sprintf may cause buffer overflow problems and is not recommended, I always prefer to use the snprintf function in the project, although it will be a little troublesome. Here is the main difference between sprintf and snprintf: snprintf ensures that the buffer does not overflow by providing the available size of the buffer and passing parameters. If it exceeds the buffer size, it is truncated.

(2) The return value of sprintf and snprintf functions

The return value of the snprintf function
The sprintf function returns the number of characters actually output to the string buffer, Including the null terminator.
The snprintf function returns the number of characters that should be output to the string buffer, So the return value of snprintf may be greater than the given available buffer size and the resulting string length.

you should check out studytonight for futher information.
Jul 8 '21 #8
priti kumari
3 New Member
1. The main differences are as follows
(1) String buffer of and functions
Because may cause buffer overflow problems and is not recommended, I always prefer to use the function in the project, although it will be a little troublesome.
(2) The return value of sprintf and snprintf function
function returns the number of characters that should be output to the string buffer, So the return value of may be greater than the given available buffer size and the
Jul 12 '21 #9
1 New Member
Thanks for this post. Just need it.
Aug 5 '21 #10

Sign in to post your reply or Sign up for a free account.

Similar topics

by: foo | last post by:
I've been looking on the web to see if I could find a link that would describe the difference between the 14882:1998 and the 14882:2003 C++ standard. I found the following link: http://www.acceleratedcpp.com/authors/koenig/c++std/revisions.pdf But the above document is over 300 pages long, and it's not practical for actually trying to determine what difference has been made that would actually effect the langauge.
by: diadia | last post by:
string s = "hello"; const char *p = s.begin(); cout << p << endl; // print hello s = ""; char *p2= s.begin(); cout << p2 << endl; // print hello why?????
by: J Wang | last post by:
dear, I debug the program recently as follows. #include <sys/stat.h> int main(int argc, char *argv) { struct stat buf;
by: programer | last post by:
Can I use Activex (as vb) to connect database when I use vc.net.
by: ajay.bansal02 | last post by:
Hi All What is difference in TCHAR myVar=.....; and TCHAR *myVAR1=(TCHAR *)malloc....; arent both myVar and myVAR1are same?
by: Dennis | last post by:
I am trying to set up an Expression column in a DataTable for display in a DataGrid that subtract the column ("BirthDay") from todays date. I can't seem to get it right...is this possible? -- Dennis in Houston
by: RupeshDeenadayalan | last post by:
Is there any difference between a boot loader and a boot strapper.It would be better if any one can tell what operations does a general bootloader,boot strapper,BSP,Driver does???
by: satty888 | last post by:
i've got a bunch of questions for coursework at uni and theres no good notes that i have or been given. can someone please tell me what a sprintf function does if it was used like this: sprintf(ok2, "Content-Type: %s\r\n\r\n", typ); thank u all who help me!
by: martin paul | last post by:
Hello Sir...Could you tell me the KEY difference between signal and sigaction functions....Kindly consider the following sample program which is using signal function... #include <signal.h> void mysighandler(void); int main () { signal(SIGINT,mysighandler); char ch; while(1) { ch=getchar();
by: bhushanbagul | last post by:
Hi All Please let me know exactly what difference i and g makes in oracle version i.e. when we say oracle 10g or oracle 11i Thanks Bhushan
by: marktang | last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look ! Part I. Meaning of...
by: Hystou | last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it. First, let's disable language synchronization. With a Microsoft account, language settings sync across devices. To prevent any complications,...
by: Oralloy | last post by:
Hello folks, I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>". The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed. This is as boiled down as I can make it. Here is my compilation command: g++-12 -std=c++20 -Wnarrowing bit_field.cpp Here is the code in...
by: jinu1996 | last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth. The Art of Business Website Design Your website is...
by: Hystou | last post by:
Overview: Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For most users, this new feature is actually very convenient. If you want to control the update process,...
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
by: agi2029 | last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own.... Now, this would greatly impact the work of software developers. The idea...
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules. He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms. Adolph will...
by: adsilva | last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.