C - 小さなツールの作成 - 1つのことだけをうまくやる(独自のデータストリーム、ファイル、fopen関数、モード(読み込み、書き込み)、fclose関数)

Head First C
原著

開発環境

• OS: macOS High Sierra - Apple
• Text Editor: Emacs
• コンパイラー: LLVM/Clang, GCC(gcc)
• プログラミング言語: C

Head First C ―頭とからだで覚えるCの基本 (David Griffiths (著)、Dawn Griffiths (著)、中田 秀基 (監修)、木下 哲也 (翻訳)、オライリージャパン)の3章(小さなツールの作成 - 1つのことだけをうまくやる)、自分で考えてみよう(p. 139)を取り組んでみる。

自分で考えてみよう(p. 139)

#include <stdio.h>
#include <string.h>

int main() {
  char line[80];
  FILE *in = fopen("spooky.csv", "r");
  FILE *file1 = fopen("ufos.csv", "w");
  FILE *file2 = fopen("disappearances.csv", "w");
  FILE *file3 = fopen("others.csv", "w");
  
  while (fscanf(in, "%79[^\n]\n", line) == 1) {
    if (strstr(line, "UFO")) {
      fprintf(file1, "%s\n", line);
    } else if (strstr(line, "Disappearance")) {
      fprintf(file2, "%s\n", line);
    } else {
      fprintf(file3, "%s\n", line);
    }
  }
  fclose(in);
  fclose(file1);
  fclose(file2);
  fclose(file3);
}

入出力結果(Terminal)

$ cc sample.c -o sample
$ ./sample 
$ cat spooky.csv
 42.363400,-71.098465,Speed = 21,Type="Mermaid"
 42.363327,-71.097588,Speed = 23,Type="UFO"
 42.363255,-71.096710,Speed = 17,Type="Disappearance"
 42.363182,-71.095833,Speed = 22,Type="UFO"
 42.363110,-71.094955,Speed = 14,Type="Goatsucker"
 42.363037,-71.094078,Speed = 16,Type="Disappearance"
 42.362965,-71.093201,Speed = 18,Type="UFO"
 42.362892,-71.092323,Speed = 22,Type="Giant octopus"
 42.362820,-71.091446,Speed = 17,Type="Disappearance"
 42.362747,-71.090569,Speed = 23,Type="UFO"
 42.362675,-71.089691,Speed = 14,Type="Elvis"
 42.362602,-71.088814,Speed = 19,Type="UFO"
 42.362530,-71.087936,Speed = 16,Type="Disappearance"
 42.362457,-71.087059,Speed = 16,Type="Disappearance"
 42.362385,-71.086182,Speed = 21,Type="Yeti"
 $ cat ufos.csv 
42.363327,-71.097588,Speed = 23,Type="UFO"
42.363182,-71.095833,Speed = 22,Type="UFO"
42.362965,-71.093201,Speed = 18,Type="UFO"
42.362747,-71.090569,Speed = 23,Type="UFO"
42.362602,-71.088814,Speed = 19,Type="UFO"
$ cat disappearances.csv 
42.363255,-71.096710,Speed = 17,Type="Disappearance"
42.363037,-71.094078,Speed = 16,Type="Disappearance"
42.362820,-71.091446,Speed = 17,Type="Disappearance"
42.362530,-71.087936,Speed = 16,Type="Disappearance"
42.362457,-71.087059,Speed = 16,Type="Disappearance"
$ cat others.csv 
 42.363400,-71.098465,Speed = 21,Type="Mermaid"
42.363110,-71.094955,Speed = 14,Type="Goatsucker"
42.362892,-71.092323,Speed = 22,Type="Giant octopus"
42.362675,-71.089691,Speed = 14,Type="Elvis"
42.362385,-71.086182,Speed = 21,Type="Yeti"
$