gistfile1.c

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>

int main() {
  int fd[2], kol = 0, i;
  char instr[30], outstr[30], symb;
  pid_t childpid;
  pipe(fd);
  if ((childpid = fork()) == -1) {
    perror("fork");
    exit(1);
  } else if (childpid == 0) {
    FILE *fil;
    fil = fopen("fil.txt", "r");
    while (fgets(instr, 30, fil) != NULL) {
      write(fd[1], instr, sizeof(char) * strlen(instr));
    }
    close(fd[0]);
    exit(0);
  } else {
    close(fd[1]);
    printf("Введите букву: \n");
    scanf("%c", &symb);
    while(read(fd[0], outstr, 30) != 0) {
      for (i = 0; i < strlen(outstr); i++) {
        if (outstr[i] == symb) { kol++; }
      }
    }
    printf("result = %i\n", kol);
  }
  return(0);
}