C strstr not working correctly

Question

I am trying to use strstr to search for any matches using a substring and comparing it to a line of text but haven't been successful in getting a match so far. I am opening and reading a file using popen while trying to do a search with only the ipv4 address looking for matches. What is wrong with my code? Any help will be much appreciated, thanks.

char *buffe = malloc(sizeof(char));

        FILE *rib_file = popen("bgpdump -Mv rib.20160101.0000.bz2", "r");
        while(fgets(buffe, sizeof(buffe), rib_file)!=NULL) {
            if(buffe[strlen(buffe)-1] == '\n')
                buffe[strlen(buffe)-1] = '\0';
          for (int i = 0; i < argc; i++) {
            if((strstr(buffe, argv[i])) != NULL) {
                printf("A match found on line: %d\n", line_num);
                printf("\n%s\n", buffe);

                find_result++;
            }
                line_num++;
          }

        }
            if(find_result == 0) {
                printf("\nSorry, couldn't find a match.\n");
            }

        if (rib_file) {
            pclose(rib_file);
        }

        free(buffe);
    }

an example of what buffe is like:

TABLE_DUMP2|01/01/16 00:00:38|B|202.232.0.3|2497|223.255.254.0/24|2497 7473 3758 55415|IGP

I am trying to print the exact line as above when my code finds a match.

We need to know things like what `buffe` is, what you're expecting this code to output, what the code does output, what input you're feeding it, and so on. — David Schwartz, Mar 08 '16 at 08:12
You don't show the whole code, but `buffe` seems to be a pointer to allocated memory, because you `free` it later. That means that `sizeof(buffe)` is smaller than you think: It's the size of a pointer, not the number of bytes allocated. — M Oehm, Mar 08 '16 at 08:12
What is the content of the file, if it is binary data strstr is not the function to use — Mindaugas, Mar 08 '16 at 08:13
And besides the above, remember that all string functions are case sensitive. — Some programmer dude, Mar 08 '16 at 08:14
You allocate 1 byte and read in `sizeof(char*)` bytes. That leads to UB. — Spikatrix, Mar 08 '16 at 08:35
How do you plan to read your file into a 1-byte memory block — M.M, Mar 08 '16 at 09:20
@Lundin that would be the right code for removing the newline appended by fgets, if earlier problems in the code were fixed (and a zero length check added) — M.M, Mar 08 '16 at 09:36

David Schwartz · Accepted Answer · 2016-03-08T16:29:27.987

2

The sizeof function tells you the size of a type. Since buffe is a pointer, your call to sizeof(buffe) will get you the size of a pointer on your platform which is almost certainly not what you want. Did you mean to pass fgets the size of the thing buffe points to?

edited Mar 08 '16 at 16:29

answered Mar 08 '16 at 08:13

David Schwartz

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C strstr not working correctly

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