Traitement des chaînes de caractères en C

$ gcc -Wall 36078402.c 
36078402.c: In function ‘main’:
36078402.c:9:18: error: ‘ligneF’ undeclared (first use in this function)
  char LF1 =fgets(ligneF,sizeof ligneF,file1);
                  ^~~~~~
36078402.c:9:18: note: each undeclared identifier is reported only once for each function it appears in
36078402.c:11:19: error: ‘ligneB’ undeclared (first use in this function)
  char LF2 = fgets(ligneB,sizeof ligneB,file2);
                   ^~~~~~
36078402.c:13:11: warning: comparison between pointer and integer
  while(LF1!=NULL && LF2 !=NULL)
           ^~
36078402.c:13:25: warning: comparison between pointer and integer
  while(LF1!=NULL && LF2 !=NULL)
                         ^~
36078402.c:15:14: warning: implicit declaration of function ‘strstr’ [-Wimplicit-function-declaration]
   char verif=strstr(LF2,LF2);
              ^~~~~~
36078402.c:15:14: warning: incompatible implicit declaration of built-in function ‘strstr’
36078402.c:15:14: note: include ‘<string.h>’ or provide a declaration of ‘strstr’
36078402.c:15:21: warning: passing argument 1 of ‘strstr’ makes pointer from integer without a cast [-Wint-conversion]
   char verif=strstr(LF2,LF2);
                     ^~~
36078402.c:15:21: note: expected ‘const char *’ but argument is of type ‘char’
36078402.c:15:25: warning: passing argument 2 of ‘strstr’ makes pointer from integer without a cast [-Wint-conversion]
   char verif=strstr(LF2,LF2);
                         ^~~
36078402.c:15:25: note: expected ‘const char *’ but argument is of type ‘char’
36078402.c:15:14: warning: initialization makes integer from pointer without a cast [-Wint-conversion]
   char verif=strstr(LF2,LF2);
              ^~~~~~
36078402.c:16:11: warning: comparison between pointer and integer
   if(verif!=NULL)
           ^~
36078402.c:18:13: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Wformat=]
    printf("%s",verif);