#define _POSIX_C_SOURCE 200809L
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>

static int
search(FILE *file, const char *pattern, const char *name)
{
    char *line = NULL;
    size_t capacity = 0;
    size_t pattern_len = strlen(pattern);
    ssize_t n;
    int matched = 0;
    while ((n = getline(&line, &capacity, file)) >= 0) {
        size_t i;
        if (pattern_len > (size_t)n) continue;
        for (i = 0; i <= (size_t)n - pattern_len; ++i)
            if (memcmp(line + i, pattern, pattern_len) == 0) break;
        if (i > (size_t)n - pattern_len) continue;
        if (fwrite(line, 1, (size_t)n, stdout) != (size_t)n) {
            perror("grep: stdout"); free(line); return 2;
        }
        matched = 1;
    }
    free(line);
    if (!feof(file)) { perror(name); return 2; }
    return matched ? 0 : 1;
}

int
main(int argc, char **argv)
{
    int i, status = 1;
    if (argc < 2) { fprintf(stderr, "usage: %s pattern [file...]\n", argv[0]); return 2; }
    if (argc == 2) status = search(stdin, argv[1], "grep: stdin");
    for (i = 2; i < argc; ++i) {
        FILE *file = strcmp(argv[i], "-") == 0 ? stdin : fopen(argv[i], "r");
        int result;
        if (file == NULL) { perror(argv[i]); status = 2; continue; }
        result = search(file, argv[1], argv[i]);
        if (result == 2) status = 2;
        else if (result == 0 && status != 2) status = 0;
        if (file != stdin && fclose(file) == EOF) { perror(argv[i]); status = 2; }
    }
    if (fflush(stdout) == EOF) { perror("grep: stdout"); status = 2; }
    return status;
}