How to use sprintf instead of hardcoded values

Question

I am developing a firewall for Linux as my project. I am able to capture packets and to block them. I am using IPTABLES.

How can I use variables with sprintf instead of hardcoded values?

sprintf(comm, "iptables -A INPUT -s $str -j DROP") // inplace of: sprintf(comm, "iptables -A INPUT -s 192.168.0.43 -j DROP")

Roger Pate · Accepted Answer · 2010-03-20 11:17:27Z

sprintf(comm, "iptables -A INPUT -s %s -j DROP", "192.168.0.43"); // also: char ipaddress[] = "192.168.0.43"; sprintf(comm, "iptables -A INPUT -s %s -j DROP", ipaddress);

Read more in man sprintf.

Roman Dmitrienko · Accepted Answer · 2010-03-20 11:25:11Z

0

It works just like regular printf(). Same format strings are accepted. However, be careful to avoid overflowing the string buffer. In that sense, snprintf() will be MUCH more acceptable than sprintf().

answered Mar 20, 2010 at 11:25

Roman Dmitrienko

4,3054 gold badges42 silver badges50 bronze badges

3 Comments

neha soni Over a year ago

thanks but it gives an error of incompatible types nw wht to do??? actually i want to use iptables commands in my c program its working for static ipaddress but i want to do that for dynamically

Roman Dmitrienko Over a year ago

What exactly does the error say? Are you following the snprintf() documentation?

Roger Pate Over a year ago

@astha: It sounds like you need to learn about general string manipulation in C, which is a stumbling block for many new programmers.

Collectives™ on Stack Overflow

How to use sprintf instead of hardcoded values

2 Answers 2

Comments

3 Comments

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

3 Comments

Related