How to Implement Grep into CGI script Please?

Question

Hi all!

I am having difficulty figuring out how to implement grep into my CGI script. Basically I will receive a value of eg. 1500 from a HTML page. The CGI script then runs and compares 1500 to a text file. When it finds 1500 it prints the entire line and displays it on the webpage. I would like some tips and pointers on how to do this please. I understand that this involves grep but I don't really know how to put it in.

#include <stdio.h>
#include <stdlib.h>
int main(void)
{
char *data;
long m,n;
printf("%s%c%c\n",
"Content-Type:text/html;charset=iso-8859-1",13,10);
printf("<TITLE>Webpage of Results</TITLE>\n");
printf("<H1>Temperatures</H1>\n");
data = getenv("QUERY_STRING");

The HTML passes the variable time=1500. I understand (correct me if I am wrong) that QUERY_STRING will contain 1500?

Answer 1

For a URL of the form whatever?query-string, the enviroment variable QUERY_STRING contains the full query-string - in you case time=1500 or similar.

You need to remember that there may be more then one field/value getting passed, seperated by &. By using strtok() you can retrieve the parts of the query string one by one, strcmp() lets you compare them to other strings.

If you found the right token, you need to work with a file:

• fopen() is used for opening a file
• fgets() is used to retrieve a line
• use strstr() to check if a line contains a certain substring
• use fclose() to close the file when you're done

Answer 2

some very straightforward analog of the grep in C is strstr() function