cut.c

   1 /*
   2     Copyright © 2013 Alastair Stuart
   3
   4     This program is open source software: you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation, either version 3 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  12     GNU General Public License for more details.
  13 */
  14
  15 #include <stdio.h>
  16 #include <stdlib.h>
  17 #include <string.h>
  18 #include <errno.h>
  19
  20 #include <sys/stat.h>
  21 #include <sys/types.h>
  22
  23 #define VERSION "0.01"
  24
  25 char delim = '\0';
  26 unsigned int field = 0;
  27
  28 int main(int argc, char* argv[])
  29 {
  30     // flag parsing
  31     int arg = 0;
  32     for (arg = 1; arg < argc; arg++)
  33     {
  34         if (strcmp("-d", argv[arg]) == 0) {
  35             delim = argv[arg + 1][0];
  36             arg++;
  37         } else if (strcmp("-f", argv[arg]) == 0) {
  38             field = atoi(argv[arg + 1]);
  39             arg++;
  40         } else if (strcmp("--help", argv[arg]) == 0 || strcmp("-h", argv[arg]) == 0) {
  41             printf("Usage: %s -d [delim] -f [field] [file]\n", argv[0]);
  42             printf("[delim] must be a character and [field] starts at 1.\n"
  43                    "\n"
  44                    "    -h, --help              Print this message.\n"
  45                    "    -v, --version           Show version info.\n");
  46             return 0;
  47         } else if (strcmp("--version", argv[arg]) == 0 || strcmp("-v", argv[arg]) == 0) {
  48             printf("cut (mutos) v"VERSION"\n");
  49             return 0;
  50         } else {
  51             // no more flags left
  52             break;
  53         }
  54     }
  55
  56     if (!field) {
  57         fprintf(stderr, "%s: you must specify a field.\n"
  58                         "Run '%s --help' for usage.\n",
  59                          argv[0], argv[0]);
  60         return 1;
  61     }
  62
  63     FILE* file   = NULL;
  64     char* buffer = NULL;
  65
  66     struct stat file_stat;
  67     int buf_size = 0;
  68     // if no file is specified or file is "-"
  69     if ((argc - arg) == 0 || strcmp(argv[arg], "-") == 0) {
  70         buffer = calloc(4096 + 1, sizeof(char));
  71         buf_size = 4096 + 1;
  72         file = stdin;
  73     } else {
  74         // stat the file to get its size
  75         // if we statted successfully,
  76         // allocate a buffer
  77         int rc = stat(argv[argc - 1], &file_stat);
  78         if (rc >= 0) {
  79             buffer = calloc(file_stat.st_size + 1, sizeof(char));
  80             buf_size = file_stat.st_size + 1;
  81             file = fopen(argv[arg], "r");
  82         } else {
  83             fprintf(stderr, "%s: %s: %s\n",
  84                              argv[0], strerror(errno), argv[argc - 1]);
  85             return 1;
  86         }
  87     }
  88
  89     int num_lines = 0;
  90
  91     int c = fgetc(file);
  92     for (int i = 0; i < buf_size && c != EOF; i++)
  93     {
  94          buffer[i] = (char)c;
  95          c = fgetc(file);
  96     }
  97     // Null-terminate the buffer
  98     buffer[buf_size - 1] = '\0';
  99
 100     // for each char in the buffer
 101     for (int i = 0; i < buf_size; i++)
 102     {
 103         if (buffer[i] == '\n') {
 104             num_lines++;
 105         }
 106     }
 107
 108     size_t line_len[num_lines];
 109     memset(line_len, 0, num_lines * sizeof(size_t));
 110
 111     char* lines[num_lines];
 112     // for each line: i = current line, j = current character
 113     for (int i = 0, j = 0, last_enter = -1; i < num_lines && j < file_stat.st_size; j++)
 114     {
 115         if (buffer[j] != '\n') {
 116             line_len[i]++;
 117         } else {
 118             // allocate a string that's the length of the current line
 119             lines[i] = malloc(line_len[i] + 1);
 120             // copy the line
 121             strncpy(lines[i], buffer+last_enter+1, line_len[i]);
 122             // set last_enter to the current enter
 123             // for the next line
 124             last_enter = j;
 125             // go to next line
 126             i++;
 127         }
 128     }
 129
 130     // delete delimiter characters by setting it to -1
 131     for (int i = 0; i < num_lines; i++)
 132     {
 133         for (size_t j = 0; j < strlen(lines[i]); j++)
 134         {
 135             if (lines[i][j] == delim) {
 136                 lines[i][j] = -1;
 137             }
 138         }
 139     }
 140
 141     // go through the line and print the requested field
 142     for (int i = 0; i < num_lines; i++)
 143     {
 144         for (size_t j = 0, field_count = 0; j < strlen(lines[i]); j++)
 145         {
 146             if (lines[i][j == 0 ? j : j - 1] == -1 && lines[i][j] != -1) {
 147                 field_count++;
 148             }
 149
 150             if (field_count == field - 1 && lines[i][j] != -1) {
 151                 printf("%c", lines[i][j]);
 152             }
 153         }
 154         printf("\n");
 155     }
 156
 157     return 0;
 158 }