├── LICENSE.md
├── Makefile
├── README.md
├── init.c
└── respawn.c


/LICENSE.md:
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 1 | Copyright © 2013-2020 Rich Felker
 2 | 
 3 | Permission is hereby granted, free of charge, to any person obtaining
 4 | a copy of this software and associated documentation files (the
 5 | "Software"), to deal in the Software without restriction, including
 6 | without limitation the rights to use, copy, modify, merge, publish,
 7 | distribute, sublicense, and/or sell copies of the Software, and to
 8 | permit persons to whom the Software is furnished to do so, subject to
 9 | the following conditions:
10 | 
11 | The above copyright notice and this permission notice shall be
12 | included in all copies or substantial portions of the Software.
13 | 
14 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
15 | EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
16 | MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
17 | IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
18 | CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
19 | TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
20 | SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
21 | 


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/Makefile:
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 1 | 
 2 | SRCS = $(wildcard *.c)
 3 | OBJS = $(SRCS:%.c=%.o)
 4 | 
 5 | CFLAGS = -O2
 6 | LDFLAGS = -s
 7 | 
 8 | all: init respawn
 9 | 
10 | clean:
11 | 	rm -f init respawn $(OBJS)
12 | 
13 | $(OBJS):
14 | 
15 | %: %.o
16 | 	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $<
17 | 
18 | %.o: %.c
19 | 	$(CC) $(CFLAGS) -c -o $@ $<
20 | 


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/README.md:
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 1 | # Minimal init
 2 | 
 3 | This is an updated, nommu-compatible version of my minimal init,
 4 | adapted from the version originally published on ewontfix.com.
 5 | 
 6 | All it does it run `/etc/rc` on startup and reap orhaned processes
 7 | as they exit. It does not do any process supervision.
 8 | 
 9 | The `respawn` utility also included is a minimal process supervisor.
10 | It's not intended for any elaborate supervision, mainly running gettys
11 | for login, started from `/etc/rc` in place of a traditional `inittab`.
12 | The entire command line `argv[1]` to `argv[argc]` is the command that
13 | is executed repeatedly, so `argv[1]` should be an absolute pathname.
14 | Bad Things will happen if it's a program which daemonizes itself.
15 | 


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/init.c:
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 1 | #include <signal.h>
 2 | #include <unistd.h>
 3 | #include <spawn.h>
 4 | #include <sys/wait.h>
 5 | 
 6 | int main()
 7 | {
 8 | 	if (getpid() != 1) return 1;
 9 | 
10 | 	sigset_t set, old;
11 | 	sigfillset(&set);
12 | 	sigprocmask(SIG_BLOCK, &set, &old);
13 | 
14 | 	posix_spawnattr_t attr;
15 | 	posix_spawnattr_init(&attr);
16 | 	posix_spawnattr_setsigmask(&attr, &old);
17 | 	posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSID|POSIX_SPAWN_SETSIGMASK);
18 | 
19 | 	posix_spawn(0, "/etc/rc", 0, &attr,
20 | 		((char *[]){ "rc", 0 }),
21 | 		((char *[]){ 0 }));
22 | 
23 | 	for (;;) wait(0);
24 | }
25 | 


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/respawn.c:
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 1 | #include <signal.h>
 2 | #include <unistd.h>
 3 | #include <fcntl.h>
 4 | #include <spawn.h>
 5 | #include <sys/wait.h>
 6 | #include <time.h>
 7 | 
 8 | int main(int argc, char **argv)
 9 | {
10 | 	sigset_t set, old;
11 | 	sigfillset(&set);
12 | 	sigprocmask(SIG_BLOCK, &set, &old);
13 | 
14 | 	posix_spawnattr_t attr;
15 | 	posix_spawnattr_init(&attr);
16 | 	posix_spawnattr_setsigmask(&attr, &old);
17 | 	posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSID|POSIX_SPAWN_SETSIGMASK);
18 | 
19 | 	for (;;) {
20 | 		extern char **environ;
21 | 		pid_t pid;
22 | 		if (posix_spawn(&pid, argv[1], 0, &attr, argv+1, environ))
23 | 			nanosleep(&(struct timespec){.tv_nsec=100000000}, 0);
24 | 		waitpid(pid, 0, 0);
25 | 	}
26 | }
27 | 


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