C - 小さなツールの作成 - 1つのことだけをうまくやる(リダイレクト、return文、エラー状態)

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)、エクササイズ(p. 115)を取り組んでみる。

エクササイズ(p. 115)

Makefile

cc = cc

all: sample run

sample: sample.c
 cc sample.c -o sample

run: sample
 ./sample

コード

#include <stdbool.h>
#include <stdio.h>

int main() {
  float latitude;
  float longitude;
  char info[80];
  bool started = false;

  puts("data=[");
  while (scanf("%f,%f,%79[^\n]", &latitude, &longitude, info) == 3) {
    if (started) {
      printf(",\n");
    } else {
      started = true;
    }
    if (latitude < -90 || 90 < latitude) {
      printf("Invalid latitude: %f\n", latitude);
      return 2;
    }
    if (longitude < -180 || 180 < longitude) {
      printf("Invalid longitude: %f\n", longitude);
      return 2;
    }
    printf("{latitude: %f, longitude: %f, info: '%s'}", latitude, longitude,
           info);
  }
  puts("\n]");
}

入出力結果(Terminal)

$ make < gpsdata.csv
./sample
data=[
{latitude: 42.363400, longitude: -71.098465, info: 'Speed = 21'},
{latitude: 42.363327, longitude: -71.097588, info: 'Speed = 23'},
{latitude: 42.363255, longitude: -71.096710, info: 'Speed = 17'},
{latitude: 42.363182, longitude: -71.095833, info: 'Speed = 22'},
{latitude: 42.363110, longitude: -71.094955, info: 'Speed = 14'},
{latitude: 42.363037, longitude: -71.094078, info: 'Speed = 16'},
{latitude: 42.362965, longitude: -71.093201, info: 'Speed = 18'},
{latitude: 42.362892, longitude: -71.092323, info: 'Speed = 22'},
{latitude: 42.362820, longitude: -71.091446, info: 'Speed = 17'},
{latitude: 42.362747, longitude: -71.090569, info: 'Speed = 23'},
{latitude: 42.362675, longitude: -71.089691, info: 'Speed = 14'},
{latitude: 42.362602, longitude: -71.088814, info: 'Speed = 19'},
{latitude: 42.362530, longitude: -71.087936, info: 'Speed = 16'},
{latitude: 42.362457, longitude: -71.087059, info: 'Speed = 16'},
{latitude: 42.362385, longitude: -71.086182, info: 'Speed = 21'}
]
$ cp gpsdata.csv gpsdata1.csv
$ echo "-100,-71.086182,'Speed = 21'" >> gpsdata1.csv
$ make < gpsdata1.csv
./sample
data=[
{latitude: 42.363400, longitude: -71.098465, info: 'Speed = 21'},
{latitude: 42.363327, longitude: -71.097588, info: 'Speed = 23'},
{latitude: 42.363255, longitude: -71.096710, info: 'Speed = 17'},
{latitude: 42.363182, longitude: -71.095833, info: 'Speed = 22'},
{latitude: 42.363110, longitude: -71.094955, info: 'Speed = 14'},
{latitude: 42.363037, longitude: -71.094078, info: 'Speed = 16'},
{latitude: 42.362965, longitude: -71.093201, info: 'Speed = 18'},
{latitude: 42.362892, longitude: -71.092323, info: 'Speed = 22'},
{latitude: 42.362820, longitude: -71.091446, info: 'Speed = 17'},
{latitude: 42.362747, longitude: -71.090569, info: 'Speed = 23'},
{latitude: 42.362675, longitude: -71.089691, info: 'Speed = 14'},
{latitude: 42.362602, longitude: -71.088814, info: 'Speed = 19'},
{latitude: 42.362530, longitude: -71.087936, info: 'Speed = 16'},
{latitude: 42.362457, longitude: -71.087059, info: 'Speed = 16'},
{latitude: 42.362385, longitude: -71.086182, info: 'Speed = 21{latitude: -100, longitude: -71.086182, info: 'Speed = 21'}'},
Invalid latitude: -100.000000
make: *** [run] Error 2
$