更改文本中的值并将其存储在C中的char数组

Question

I need some information regarding a scenario where I have an array stored with SIP INVITE message

char array_invite[] =        "INVITE sip:302@1.2.3.4 SIP/2.0\r\n"
                             "Via:SIP/2.0/UDP 5.6.7.8:39708;\r\n"
                             "Max-Forwards: 70\r\n"
                             "Contact:<sip:305@ 5.6.7.8>\r\n"
                             "To: <sip:302@1.2.3.4>; \r\n"
                             "From: \042Client\042<sip:305@5.6.7.8>;\r\n"
                             "Call-ID: abcdefg\r\n"
                             "CSeq: 1 INVITE\r\n"
                             "Content-Type: application/sdp\r\n"
                             "Content-Length: 142\r\n";

I want to change the hard code values for the IP Address (1.2.3.4 and 5.6.7.8) and the ID number(302 and 305) and make it dynamic such that I want to enter the values manually in my terminal output so that for each session I can connect to different remote addresses. Since I am not that fluent in CI am posting this question.

Anybody has an idea of how this can be done in C, may be an example would be good

Regards Dev

Answer 1

Using sprintf will work.

char array_invite[MAXLENGTH];
sprintf(array_invite,"Meet me at port %d\n",portnum);

Answer 2

You should use snprintf() to build the string from a formatting "template", like so:

char buffer[4096];
int ip{[4];

ip[0] = 1;
ip[1] = 2;
ip[2] = 3;
ip[3] = 4;

snprintf(buffer, sizeof buffer, "INVITE sip:302@%d.%d.%d.%d SIP/2.0\r\n"
                             "Via:SIP/2.0/UDP 5.6.7.8:39708;\r\n"
                             "Max-Forwards: 70\r\n"
                             "Contact:<sip:305@ 5.6.7.8>\r\n"
                             "To: <sip:302@1.2.3.4>; \r\n"
                             "From: \042Client\042<sip:305@5.6.7.8>;\r\n"
                             "Call-ID: abcdefg\r\n"
                             "CSeq: 1 INVITE\r\n"
                             "Content-Type: application/sdp\r\n"
                             "Content-Length: 142\r\n", ip[0], ip[1], ip[2], ip[3]);

Here, I only templatized the first IP address, and represented it as four int :s. You will need to extend this for the rest of the fields that you want to format dynamically.