diff --git a/i3bar/src/child.c b/i3bar/src/child.c index fa70f452..3f927b45 100644 --- a/i3bar/src/child.c +++ b/i3bar/src/child.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -100,41 +101,67 @@ void child_sig_cb(struct ev_loop *loop, ev_child *watcher, int revents) { /* * Start a child-process with the specified command and reroute stdin. * We actually start a $SHELL to execute the command so we don't have to care - * about arguments and such + * about arguments and such. + * We also double-fork() to avoid zombies and pass the pid of the child through a + * temporary pipe back to i3bar * */ void start_child(char *command) { child_pid = 0; if (command != NULL) { - int fd[2]; + int fd[2], tmp[2]; + /* This pipe will be used to communicate between e.g. i3status and i3bar */ pipe(fd); - child_pid = fork(); - switch (child_pid) { + /* We also need this temporary pipe to get back the pid of i3status */ + pipe(tmp); + switch (fork()) { case -1: ELOG("Couldn't fork()\n"); exit(EXIT_FAILURE); case 0: - /* Child-process. Reroute stdout and start shell */ - close(fd[0]); + /* Double-fork(), so the child gets reparented to init */ + switch(child_pid = fork()) { + case -1: + ELOG("Couldn't fork() twice\n"); + exit(EXIT_FAILURE); + case 0: + /* Child-process. Reroute stdout and start shell */ + close(fd[0]); - dup2(fd[1], STDOUT_FILENO); + dup2(fd[1], STDOUT_FILENO); - static const char *shell = NULL; + static const char *shell = NULL; - if ((shell = getenv("SHELL")) == NULL) - shell = "/bin/sh"; + if ((shell = getenv("SHELL")) == NULL) + shell = "/bin/sh"; - execl(shell, shell, "-c", command, (char*) NULL); - return; + execl(shell, shell, "-c", command, (char*) NULL); + return; + default: + /* Temporary parent. We tell i3bar about the pid of i3status and exit */ + write(tmp[1], &child_pid, sizeof(int)); + close(tmp[0]); + close(tmp[1]); + exit(EXIT_SUCCESS); + } default: /* Parent-process. Rerout stdin */ close(fd[1]); dup2(fd[0], STDIN_FILENO); + /* We also need to get the pid of i3status from the temporary pipe */ + size_t rec = 0; + while (rec < sizeof(int)) { + rec += read(tmp[0], &child_pid, sizeof(int) - rec); + } + /* The temporary pipe is no longer needed */ + close(tmp[0]); + close(tmp[1]); break; } } + wait(0); /* We set O_NONBLOCK because blocking is evil in event-driven software */ fcntl(STDIN_FILENO, F_SETFL, O_NONBLOCK);