filterline.c

//  Copyright 2015 by Leipzig University Library, http://ub.uni-leipzig.de
//                 by The Finc Authors, http://finc.info
//                 by Martin Czygan, <martin.czygan@uni-leipzig.de>
//
// This file is part of some open source application.
//
// Some open source application is free software: you can redistribute
// it and/or modify it under the terms of the GNU General Public
// License as published by the Free Software Foundation, either
// version 3 of the License, or (at your option) any later version.
//
// Some open source application is distributed in the hope that it will
// be useful, but WITHOUT ANY WARRANTY; without even the implied warranty
// of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Foobar.  If not, see <http://www.gnu.org/licenses/>.
//
// @license GPL-3.0+ <http://spdx.org/licenses/GPL-3.0+>
//
// filterline: filter file by line number.
// http://unix.stackexchange.com/a/209470/376
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static const char* PROGRAM_VERSION = "0.1.4";

int main(int argc, char* argv[])
{

    FILE* L;
    FILE* F;

    unsigned int to_print;
    unsigned int current = 0;
    int invertMatches = 0; // 0 = keep lines in L, 1 = drop lines in L.
    char* line = NULL;
    size_t len = 0;

    char* VERSION = "-V";
    char* flagInvert = "-v";

    if (argc == 2 && strcmp(argv[1], VERSION) == 0) {
        printf("%s\n", PROGRAM_VERSION);
        return 0;
    }

    if (argc != 3 && argc != 4) {
        printf("Usage: %s [-v] FILE1 FILE2\n\n", argv[0]);
        printf("FILE1: line numbers (sorted, no dups, one-based), FILE2: input file\n");
        printf("-v : print all lines in F not named in L (invert)\n");
        printf("-V : print version and exit\n");
        return 0;
    }

    char* lfile = argv[1];
    char* ffile = argv[2];

    if (argc == 4 && strcmp(argv[1], flagInvert) == 0) {
        invertMatches = 1;
        lfile = argv[2];
        ffile = argv[3];
    }

    if ((L = fopen(lfile, "r")) == NULL) {
        return 1;
    } else if ((F = fopen(ffile, "r")) == NULL) {
        fclose(L);
        return 1;
    } else {
        if (invertMatches == 0) {
            while (fscanf(L, "%u", &to_print) > 0) {
                while (getline(&line, &len, F) != -1 && ++current != to_print)
                    ;
                if (current == to_print) {
                    printf("%s", line);
                }
            }
        } else {
            while (fscanf(L, "%u", &to_print) > 0) {
                while (getline(&line, &len, F) != -1 && ++current != to_print)
                    printf("%s", line);
                ;
            }
            while (getline(&line, &len, F) != -1)
                printf("%s", line);
            ;
        }
        fflush(stdout);
        free(line);
        fclose(L);
        fclose(F);
        return 0;
    }
}