Thread: Reading Matching strings from a file and deleting from another.

Hello I'm working on this code for the school and we are generating emails for freshman students, however, the system probably due to server overload fails to generate some emails. So I'm working on this c code( probably was a wrong choice) to search for regexp matching the generated emails and deleting from the list of students and propective emails.

I"m currently at the stage of making sure the code can find all the matching regexp from the student list file before deleting!

But the code fails to read all matching regexp?

Code:

//Filename: SearchReplace.c
//Usage: This searches for lines in a file containing a particular work and deletes the lines.
//Licence: GNU P.L.


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>


#define BUF_SIZE 1000
char buffer[BUF_SIZE];


int read_str(char *s, FILE *fp) {

    int i = 0;
    char c;
    for( i = 0; i < 30;i++)
         s[i] = ' ';

    i = 0;

    while(( c = fgetc(fp)) != ',') {
          if(c == EOF)
              return -1;

          if(!isspace(c) && c != '\n')
             s[i++] = c;
    }

    s[i] = '\0';
    printf("\nRead String: %s\n\n", s);

    return 1;
}


int main(int argc, char *argv[]) {

    //reads the strings from an input file 
    FILE *fp = fopen(argv[1],"r");
    if( fp == NULL) {
        fprintf(stderr,"\nInvalid Input file.");
       exit(EXIT_SUCCESS);
    }

    FILE *file = fopen(argv[2], "r+");
        if( file == NULL) {
            fprintf(stderr,"\nInvalid CSV file.");
            exit(EXIT_SUCCESS);
    } 

    //writes the output to this file.
    
    char str[30];
    int i = 0;

    while( read_str(str,fp) != -1) {
  
        //searches CSV file and prints the lines with no matches to the same file.
        for( i = 0; fgets(buffer, sizeof(buffer), file);i++){
               printf("\n Buffer: %s", buffer);
               printf("\n String: %s", str);

             if( strcasestr(buffer, str) == 1){
                  //writes matching strings.
                 printf("String: %s, Buffer: %s\n",str, buffer);
    
             }
        }
        i = 0;
        rewind(file);//resets file pointer to beginning.    
    }

    fclose(fp);
    fclose(file);

    return 0;

}

Hope someone could give me a hint on what i'm missing. It recognises some regexp and fails to recognise some. Been staring for hours!

Indent style - Wikipedia, the free encyclopedia
Use this knowledge to present us with readable code.

> It recognises some regexp and fails to recognise some. Been staring for hours!
strcasestr doesn't do regular expressions.

Code:

    while( read_str(str,fp) != -1) {
   
        //searches CSV file and prints the lines with no matches to the same file.
        for( i = 0; fgets(buffer, sizeof(buffer), file);i++){
               printf("\n Buffer: %s", buffer);
               printf("\n String: %s", str);
 
             if( strcasestr(buffer, str) == 1){

I suggest you read the manual page for strcasestr to find out what it actually returns.
strcasestr(3): locate substring - Linux man page
For example, this version returns a pointer, so comparing the result with 1 is just not going to work.

Remember, things like strcmp() return 0 on success, not 1.

> So what does strcasestr do?
I'm dismayed that you even need to ask.
RTFM before using a function if you're in ANY doubt at all as to how it is supposed to work.
strcasestr isn't even a standard function, so it's anyone's guess as to what it does on YOUR platform.