/* vi: set sw=4 ts=4: */
/*
 * uniq implementation for busybox
 *
 * Copyright (C) 2005  Manuel Novoa III  <mjn3@codepoet.org>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
 
/* BB_AUDIT SUSv3 compliant */
/* http://www.opengroup.org/onlinepubs/007904975/utilities/uniq.html */
 
//usage:#define uniq_trivial_usage
//usage:       "[-cdu][-f,s,w N] [INPUT [OUTPUT]]"
//usage:#define uniq_full_usage "\n\n"
//usage:       "Discard duplicate lines\n"
//usage:     "\n    -c    Prefix lines by the number of occurrences"
//usage:     "\n    -d    Only print duplicate lines"
//usage:     "\n    -u    Only print unique lines"
//usage:     "\n    -f N    Skip first N fields"
//usage:     "\n    -s N    Skip first N chars (after any skipped fields)"
//usage:     "\n    -w N    Compare N characters in line"
//usage:
//usage:#define uniq_example_usage
//usage:       "$ echo -e \"a\\na\\nb\\nc\\nc\\na\" | sort | uniq\n"
//usage:       "a\n"
//usage:       "b\n"
//usage:       "c\n"
 
#include "libbb.h"
 
int uniq_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int uniq_main(int argc UNUSED_PARAM, char **argv)
{
    const char *input_filename;
    unsigned skip_fields, skip_chars, max_chars;
    unsigned opt;
    char *cur_line;
    const char *cur_compare;
 
    enum {
        OPT_c = 0x1,
        OPT_d = 0x2, /* print only dups */
        OPT_u = 0x4, /* print only uniq */
        OPT_f = 0x8,
        OPT_s = 0x10,
        OPT_w = 0x20,
    };
 
    skip_fields = skip_chars = 0;
    max_chars = INT_MAX;
 
    opt_complementary = "f+:s+:w+";
    opt = getopt32(argv, "cduf:s:w:", &skip_fields, &skip_chars, &max_chars);
    argv += optind;
 
    input_filename = argv[0];
    if (input_filename) {
        const char *output;
 
        if (input_filename[0] != '-' || input_filename[1]) {
            close(STDIN_FILENO); /* == 0 */
            xopen(input_filename, O_RDONLY); /* fd will be 0 */
        }
        output = argv[1];
        if (output) {
            if (argv[2])
                bb_show_usage();
            if (output[0] != '-' || output[1]) {
                // Won't work with "uniq - FILE" and closed stdin:
                //close(STDOUT_FILENO);
                //xopen(output, O_WRONLY | O_CREAT | O_TRUNC);
                xmove_fd(xopen(output, O_WRONLY | O_CREAT | O_TRUNC), STDOUT_FILENO);
            }
        }
    }
 
    cur_compare = cur_line = NULL; /* prime the pump */
 
    do {
        unsigned i;
        unsigned long dups;
        char *old_line;
        const char *old_compare;
 
        old_line = cur_line;
        old_compare = cur_compare;
        dups = 0;
 
        /* gnu uniq ignores newlines */
        while ((cur_line = xmalloc_fgetline(stdin)) != NULL) {
            cur_compare = cur_line;
            for (i = skip_fields; i; i--) {
                cur_compare = skip_whitespace(cur_compare);
                cur_compare = skip_non_whitespace(cur_compare);
            }
            for (i = skip_chars; *cur_compare && i; i--) {
                ++cur_compare;
            }
 
            if (!old_line || strncmp(old_compare, cur_compare, max_chars)) {
                break;
            }
 
            free(cur_line);
            ++dups;  /* testing for overflow seems excessive */
        }
 
        if (old_line) {
            if (!(opt & (OPT_d << !!dups))) { /* (if dups, opt & OPT_u) */
                if (opt & OPT_c) {
                    /* %7lu matches GNU coreutils 6.9 */
                    printf("%7lu ", dups + 1);
                }
                printf("%s\n", old_line);
            }
            free(old_line);
        }
    } while (cur_line);
 
    die_if_ferror(stdin, input_filename);
 
    fflush_stdout_and_exit(EXIT_SUCCESS);
}

#include <assert.h>
#include <lauxlib.h>
#include <lualib.h>
#include <string.h>

int main() {
	const char *prog_uniq = ""
		"prev = nil\n"
		"for line in io.stdin:lines() do\n"
		"	if line ~= prev then\n"
		"		print(line)\n"
		"		prev = line\n"
		"	end\n"
		"end";
	lua_State *L = luaL_newstate();
	assert(L);
	luaL_openlibs(L);
	int r = luaL_loadbuffer(L, prog_uniq, strlen(prog_uniq), "uniq");
	assert(r == LUA_OK);
	lua_call(L, 0, 0);
	return 0;
}

$ gcc -l lua5.2 -I /usr/include/lua5.2/ c.c
$ { seq 4 ; seq 2 ; } | sort | ./a.out 
1
2
3
4

#include <assert.h>
#include <lauxlib.h>
#include <lualib.h>