C - プロセス間通信: お話は楽しい(パイプ)

Head First C ―頭とからだで覚えるCの基本
(オライリージャパン)
David Griffiths (著) Dawn Griffiths (著)
中田 秀基(監訳)(翻訳) 木下 哲也 (翻訳)

開発環境

• OS X Yosemite - Apple (OS)
• Emacs (CUI)、BBEdit - Bare Bones Software, Inc. (GUI) (Text Editor)
• C (プログラミング言語)
• LLVM/Clang (コンパイラ, Xcode - Apple)

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(監訳)(翻訳)、木下 哲也 (翻訳)、オライリージャパン)の10章(プロセス間通信: お話は楽しい)、エクササイズ(p.447)を解いてみる。

その他参考書籍

• 21st Century C: C Tips from the New School
• プログラミング言語C 第2版 ANSI規格準拠 (B.W. カーニハン D.M. リッチー (著)、 石田 晴久 (翻訳)、共立出版)
• プログラミング言語Cアンサー・ブック 第2版 (クロビス・L．トンド、スコット・E．ギンペル(著)、矢吹 道郎(翻訳))
• C実践プログラミング 第3版 (Steve Oualline (著)、 望月 康司 (監訳) (翻訳)、 谷口 功 (翻訳)、 オライリージャパン)

エクササイズ(p.447)

コード(BBEdit, Emacs)

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <stopif.h>

void open_url(char *url) {
  char *launch;
  asprintf(&launch, "cmd /c start %s", url);
  system(launch);
  asprintf(&launch, "x-www-browser '%s' &", url);
  system(launch);
  asprintf(&launch, "open '%s'", url);
  system(launch);
}

int main(int argc, char **argv) {
  int fd[2];
  Stopif(pipe(fd) == -1, exit(1), "パイプを作成できません");
  
  pid_t pid = fork();
  Stopif(pid == -1, exit(1), "プロセスをフォークできません");
  
  if (!pid) {
    close(fd[0]);
    dup2(fd[1], 1);

    char *phrase = argv[1];
    char *vars[] = {"RSS_FEED=http://rss.cnn.com/rss/edition.rss", NULL};
    Stopif(execle("/usr/bin/python", "/usr/bin/python", "rssgossip.py", "-u",
                  phrase, NULL, vars) == -1,
           exit(1),
           "スクリプトを実行できません");
  }
  dup2(fd[0], 0);
  close(fd[1]);
  char line[255];
  while (fgets(line, 255, stdin)) {
    printf("%s\n", line);
    if (line[0] == '\t') open_url(line + 1);
  }
}

入出力結果(Terminal)

$ make news_opener
clang ...
$ ./news_opener US
Eritrea's vast, vile 'abuses'

 http://edition.cnn.com/2015/06/09/world/eritrea-human-rights-violations/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
White House rooms evacuated

 http://edition.cnn.com/2015/06/09/politics/hearing-evacuated-bomb-threat-tsa/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
Meet the female Muslim wrestlers

 http://edition.cnn.com/2015/06/09/sport/european-games-azerbaijan-wrestling/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
Russia's stars eye gold at beach soccer

 http://edition.cnn.com/2015/06/03/sport/baku-azerbaijan-european-games-beach-soccer/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
Maths genius' mansion: Yours for $23M

 http://edition.cnn.com/2015/06/04/travel/curve-house-23-million-integral-toronto/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
Business advice from Jay-Z, Beyonce

 http://edition.cnn.com/2015/06/09/world/how-to-start-your-own-charity/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
Thousands rescued in 'migrant season' 

 http://edition.cnn.com/video/data/2.0/video/tv/2015/06/09/rescued-in-migrant-season-robertson-pkg.cnn.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
Could Russia, Qatar 'lose World Cup rights'?

 http://edition.cnn.com/2015/06/08/football/fifa-scandal/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
What weaponry is ISIS using?

 http://edition.cnn.com/2015/06/09/opinions/isis-iraq-weapons/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
Why Jerusalem is such a sticky issue

 http://edition.cnn.com/2015/06/08/opinions/ghitis-supreme-court-jerusalem/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
The homeowners who refused to budge

 http://edition.cnn.com/2015/05/19/asia/gallery/china-nail-houses/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
The most ambitious luxury home ever?

 http://edition.cnn.com/2015/06/03/americas/architect-3d-prints-luxury-estate/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
Stunning images: Chinese houses laid bare

 http://edition.cnn.com/2015/05/18/asia/china-families-belongings/index.html?eref=edition

sh: cmd: command not found
sh: line 1: x-www-browser: command not found
$