mirror of
https://github.com/troglobit/libite.git
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Joachim Wiberg
92bb0ca399
The runbg() function is a delayed execvp() that has double-forked to the background (to not create zombies). It is useful for running commands in the background for APIs that need to return a reply, e.g. a NETCONF RPC to reboot the system. Compared to the original in Infix, this version double forks to reparent itself to PID 1 (init), closes all open files, including stdio. Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
94 lines
2.4 KiB
C
94 lines
2.4 KiB
C
/* Run a command in the background: fork() + usleep() + execvp()
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*
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* Copyright (c) 2023 Joachim Wiberg <troglobit@gmail.com>
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/**
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* @file runbg.c
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* @author Joachim Wiberg
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* @date 2023
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* @copyright ISC License
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*/
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <unistd.h>
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/**
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* Run command in the background
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* @param cmd NULL terminated list of command and optional arguments
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* @param delay Microseconds after fork() to wait before calling cmd
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*
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* This function forks to run the given command @p cmd in the background.
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* To ensure there are no lingering zombies the function actuall forks
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* twice, and also calls setsid(), before it calls usleep() with the @p
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* delay argument. The command @p cmd is handed over to execvp().
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*
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* Since it runs in the background it is not possible to get the return
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* code of the command.
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*
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* @returns on successful (first) fork(), this function returns POSIX
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* OK(0), otherwise -1 and @a errno is set to indicate the error.
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*/
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int runbg(char *const cmd[], int delay)
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{
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int pid = fork();
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int rc;
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if (!pid) {
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int fd, maxfd;
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if (setsid() == -1)
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_exit(errno);
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/* reparent to init */
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pid = fork();
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if (pid == -1)
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_exit(errno);
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if (pid > 0)
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_exit(0);
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maxfd = sysconf(_SC_OPEN_MAX);
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if (maxfd == -1)
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maxfd = 8192;
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for (fd = 0; fd < maxfd; fd++)
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close(fd);
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usleep(delay);
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_exit(execvp(cmd[0], cmd));
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}
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if (pid == -1)
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return -1;
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if (waitpid(pid, &rc, 0) == -1)
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return -1;
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if (WIFEXITED(rc)) {
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errno = WEXITSTATUS(rc);
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if (errno)
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rc = -1;
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else
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rc = 0;
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} else if (WIFSIGNALED(rc)) {
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errno = EINTR;
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rc = -1;
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} else
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rc = -1;
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return rc;
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}
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