How to use strstr() function to compare content in character arrays in C? -

the purpose of small program compare strings in 2 separate files (file1.csv , file2.csv), , gives results file3.csv. if strings in file2.csv found in file1.csv, program copies strings in file1.csv file3.csv.

content of file1.csv (with 6 columns):

10000001    text1   text1   text1   text1   text1 10000002    text2   text2   text2   text2   text2 10000003    text3   text3   text3   text3   text3 10000004    text4   text4   text4   text4   text4 10000005    text5   text5   text5   text5   text5 10000006    text6   text6   text6   text6   text6 10000007    text7   text7   text7   text7   text7 10000008    text8   text8   text8   text8   text8 10000009    text9   text9   text9   text9   text9 10000010    text10  text10  text10  text10  text10 10000011    text11  text11  text11  text11  text11 10000012    text12  text12  text12  text12  text12 10000013    text13  text13  text13  text13  text13 10000014    text14  text14  text14  text14  text14 10000015    text15  text15  text15  text15  text15 10000016    text16  text16  text16  text16  text16 10000017    text17  text17  text17  text17  text17 10000018    text18  text18  text18  text18  text18 10000019    text19  text19  text19  text19  text19 10000020    text20  text20  text20  text20  text20 10000021    text21  text21  text21  text21  text21 10000022    text22  text22  text22  text22  text22 10000023    text23  text23  text23  text23  text23 10000024    text24  text24  text24  text24  text24 10000025    text25  text25  text25  text25  text25 

content of file2.csv (only 1 column):

10000001 10000003 10000004 10000006 10000007 10000008 10000009 10000011 10000012 10000015 10000025 

the expected results be:

10000001    text1   text1   text1   text1   text1 10000003    text3   text3   text3   text3   text3 10000004    text4   text4   text4   text4   text4 10000006    text6   text6   text6   text6   text6 10000007    text7   text7   text7   text7   text7 10000008    text8   text8   text8   text8   text8 10000009    text9   text9   text9   text9   text9 10000011    text11  text11  text11  text11  text11 10000012    text12  text12  text12  text12  text12 10000015    text15  text15  text15  text15  text15 10000025    text25  text25  text25  text25  text25 

i used strstr() function compare strings didn't work, code listed below:

#include <stdio.h> #include <stdlib.h> #include <string.h>  int main() {     char line[150][80] = {0};       char line2[150][80] = {0};        int = 0, b = 0;      file *file1 = fopen("file1.csv", "r");     file *file2 = fopen("file2.csv", "r");     file *file3 = fopen("file3.csv", "w");      while (fscanf(file1, "%79[^\n]\n", line[i]) != eof) {         i++;         while (fscanf(file2, "%79[^\n]\n", line2[b]) != eof) {             b++;         }         if (strstr(line[i],line2[b]))         fprintf(file3, "%s\n", line[i]);      }      fclose(file1);     fclose(file2);     fclose(file3);     return 0; } 

thanks in advance!

as unwind , other commenters rightly noted, there's no point re-reading file2.csv on every file1.csv reading iteration. read once , loop through line2[] array then.

second, may process file1.csv line-by-line , forget current line's contents it's been processed, making line[][] array unnecessary.

here's amended code:

#include <stdio.h> #include <stdlib.h> #include <string.h>  #define check_file_open(file, name) \     if (file == null) { \         printf("failed open %s\n", name); \         return 1; \     }  int main() {     char line[150] = "";       char line2[150][80] = {0};      int b = 0;     int filtercount = 0;      file *file1 = fopen("file1.csv", "r");     check_file_open(file1, "file1.csv");     file *file2 = fopen("file2.csv", "r");     check_file_open(file2, "file2.csv");     file *file3 = fopen("file3.csv", "w");     check_file_open(file3, "file3.csv");      while (fscanf(file2, "%79[^\n]\n", line2[b]) != eof) {         b++;     }     filtercount = b;     while (fscanf(file1, "%79[^\n]\n", line) != eof) {         (b = 0; b < filtercount; b++) {             if (strstr(line,line2[b])) {                 fprintf(file3, "%s\n", line);                 break;             }         }      }      fclose(file1);     fclose(file2);     fclose(file3);     return 0; } 

however, input data seems specific enough make optimization assumptions. in particular, (a) files ordered first column value , (b) second reduced copy of first (in terms of line index values).

in case might want implement one-pass processing. scan both files line line comparing index values. advance next line of first file on every iteration. of second file, move next line when current line found in first file.

#include <stdio.h> #include <stdlib.h> #include <string.h>  #define check_file_open(file, name) \     if (file == null) { \         printf("failed open %s\n", name); \         return 1; \     }  int main() {     char line1[150] = "";       char line2[150] = "";      file *file1 = fopen("file1.csv", "r");     check_file_open(file1, "file1.csv");     file *file2 = fopen("file2.csv", "r");     check_file_open(file2, "file2.csv");     file *file3 = fopen("file3.csv", "w");     check_file_open(file3, "file3.csv");      bool eof1 = fscanf(file1, "%79[^\n]\n", line1) == eof;     bool eof2 = fscanf(file2, "%79[^\n]\n", line2) == eof;      while (!eof1 && !eof2) {         if (strstr(line1, line2)) {             fprintf(file3, "%s\n", line1);             eof2 = fscanf(file2, "%79[^\n]\n", line2) == eof;         }         eof1 = fscanf(file1, "%79[^\n]\n", line1) == eof;     }      fclose(file1);     fclose(file2);     fclose(file3);     return 0; }