s6-fghack.html (1746B)
1 <html> 2 <head> 3 <meta name="viewport" content="width=device-width, initial-scale=1.0" /> 4 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 5 <meta http-equiv="Content-Language" content="en" /> 6 <title>s6: the s6-fghack program</title> 7 <meta name="Description" content="s6: the s6-fghack program" /> 8 <meta name="Keywords" content="s6 command s6-fghack foreground program background hack anti-backgrounding tool" /> 9 <!-- <link rel="stylesheet" type="text/css" href="//skarnet.org/default.css" /> --> 10 </head> 11 <body> 12 13 <p> 14 <a href="index.html">s6</a><br /> 15 <a href="//skarnet.org/software/">Software</a><br /> 16 <a href="//skarnet.org/">skarnet.org</a> 17 </p> 18 19 <h1> The s6-fghack program </h1> 20 21 <p> 22 s6-fghack is an anti-backgrounding tool. 23 </p> 24 25 <h2> Interface </h2> 26 27 <pre> 28 s6-fghack <em>prog...</em> 29 </pre> 30 31 <ul> 32 <li> s6-fghack opens a lot of file descriptors (all writing to a single pipe). </li> 33 <li> Then it spawns <em>prog...</em> as a child. </li> 34 <li> If something gets written on one of those descriptors, it's a bug in <em>prog</em>. 35 s6-fghack then complains and exits 102. </li> 36 <li> Unless <em>prog...</em> goes out of its way to close descriptors it does not know about, 37 s6-fghack is able to detect when <em>prog...</em> exits. It exits with an 38 <a href="//skarnet.org/software/execline/exitcodes.html">approximation</a> of the same exit 39 code. </li> 40 </ul> 41 42 <h2> Notes </h2> 43 44 <p> 45 s6-fghack is what it says: a hack. Ideally, you should never have to use it. 46 It is only useful when you want to supervise a daemon that does not provide a 47 "stay in the foreground" option; and even then, the right thing is to report 48 this as a bug to the daemon author and have it fixed. 49 </p> 50 51 </body> 52 </html>