How do I search a string in a file in C programming?

#include stdio.h #include string.h #include stdlib.h #ifdef DEBUG #define INITIAL_ALLOC 2 #else #define INITIAL_ALLOC 512 #endif char * read_line(FILE *fin) { char *buffer; char *tmp; int read_chars = 0; int bufsize = INITIAL_ALLOC; char *line = malloc(bufsize); if ( !line ) { return NULL; } buffer = line; while ( fgets(buffer, bufsize - read_chars, fin) ) { read_chars = strlen(line); if ( line[read_chars - 1] == '\n' ) { line[read_chars - 1] = '\0'; return line; } else { bufsize = 2 * bufsize; tmp = realloc(line, bufsize); if ( tmp ) { line = tmp; buffer = line + read_chars; } else { free(line); return NULL; } } } return NULL; } int main(int argc, char *argv[]) { FILE *fin; char *line; if ( argc != 3 ) { return EXIT_FAILURE; } fin = fopen(argv[1], "r"); if ( fin ) { while ( line = read_line(fin) ) { if ( strstr(line, argv[2]) ){ fprintf(stdout, "%s\n", line); } free(line); } } fclose(fin); return 0; } read less