Sep 9, 2014 - 1 minute read - Comments - Linux


最近は daemon って手続きがある模様。何してるかというと

  • fork でプロセスのコピィを作って
  • daemon の呼び出し元は _exit する
  • コピィの親は init になる


man してみたら出たのでそのまま引用。

NAME daemon - run in the background

SYNOPSIS #include <unistd.h>

   int daemon(int nochdir, int noclose);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

   daemon(): _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)

DESCRIPTION The daemon() function is for programs wishing to detach themselves from the controlling terminal and run in the background as sys‐ tem daemons.

   If nochdir is zero, daemon() changes the calling process's current working directory to the root directory ("/");  otherwise,  the
   current working directory is left unchanged.

   If  noclose is zero, daemon() redirects standard input, standard output and standard error to /dev/null; otherwise, no changes are
   made to these file descriptors.

RETURN VALUE (This function forks, and if the fork(2) succeeds, the parent calls _exit(2), so that further errors are seen by the child only.) On success daemon() returns zero. If an error occurs, daemon() returns -1 and sets errno to any of the errors specified for the fork(2) and setsid(2).

ディレクトリはそのままで、標準入出力を /dev/null に向ける場合は

int nochdir_ = 0;
int close_ = 1;
daemon(nochdir_, close_);


これ、でびあんで start-stop-daemon なソレを作る場合、どうやるのだったか。

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