executes commands upon file system events (using inotify)
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/*
* Copyright (c) 2014-2020 Albert S. <adhocify@quitesimple.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <sys/inotify.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
#include <libgen.h>
#include <inttypes.h>
#include <time.h>
#include <stdbool.h>
#include <stdarg.h>
#include <errno.h>
#include <fnmatch.h>
#include <getopt.h>
#include <ftw.h>
#include <linux/limits.h>
#define BUF_SIZE (sizeof(struct inotify_event) + NAME_MAX + 1) * 1024
#define STREQ(s1, s2) (strcmp(s1, s2) == 0)
#define SCRIPT_PLACE_SPECIFIER "{}" // same as EVENTFILE_PLACEHOLDER for backwards compatibility
#define EVENTFILE_PLACEHOLDER "%eventfilepath%"
#define EVENTSTR_PLACEHOLDER "%eventmaskstr%"
struct watchlistentry
{
int ifd;
char *path;
bool isdir;
struct watchlistentry *next;
};
struct watchlistentry *watchlist_head = NULL;
struct watchlistentry **watchlist = &watchlist_head;
struct ignorelist
{
char *ignore;
struct ignorelist *next;
};
struct ignorelist *ignorelist_head = NULL;
struct ignorelist **ignorelist_current = &ignorelist_head;
/* Write-once globals. Set from process_arguments*/
bool silent = false;
bool noenv = false;
bool fromstdin = false;
bool forkbombcheck = true;
bool daemonize = false;
bool exit_with_child = false;
int awaited_child_exit_code = -1;
bool negate_child_exit_code = false;
uint32_t mask = 0;
char *prog = NULL;
char *path_logfile = NULL;
char **script_arguments = NULL; // options to be passed to script we are calling
size_t n_script_arguments = 0;
void *xmalloc(size_t size)
{
void *m = malloc(size);
if(m == NULL)
{
perror("malloc");
exit(EXIT_FAILURE);
}
return m;
}
char *xstrdup(const char *s)
{
char *tmp = strdup(s);
if(tmp == NULL)
{
perror("strdup");
exit(EXIT_FAILURE);
}
return tmp;
}
char *xrealpath(const char *path, char *resolved_path)
{
char *tmp = realpath(path, resolved_path);
if(tmp == NULL)
{
char *errorstr = strerror(errno);
fprintf(stderr, "realpath on %s failed: %s\n", path, errorstr);
exit(EXIT_FAILURE);
}
return tmp;
}
char *ndirname(const char *path)
{
if(path == NULL)
{
return xstrdup(".");
}
char *c = strdupa(path);
return xstrdup(dirname(c));
}
char *find_ifd_path(int ifd)
{
for(struct watchlistentry *lkp = watchlist_head; lkp != NULL; lkp = lkp->next)
{
if(lkp->ifd == ifd)
{
return lkp->path;
}
}
return NULL;
}
bool is_ignored(const char *filename)
{
for(struct ignorelist *l = ignorelist_head; l != NULL; l = l->next)
{
if(fnmatch(l->ignore, filename, 0) == 0)
{
return true;
}
}
return false;
}
bool path_is_directory(const char *path)
{
struct stat sb;
int r = stat(path, &sb);
if(r == -1)
{
perror("stat");
return false;
}
return S_ISDIR(sb.st_mode);
}
static inline bool file_exists(const char *path)
{
return access(path, F_OK) == 0;
}
void add_to_ignore_list(const char *str)
{
*ignorelist_current = xmalloc(sizeof(struct ignorelist));
(*ignorelist_current)->ignore = xstrdup(str);
ignorelist_current = &(*ignorelist_current)->next;
}
void logwrite(const char *format, ...)
{
if(silent)
{
return;
}
va_list args;
va_start(args, format);
vfprintf(stdout, format, args);
fflush(stdout);
va_end(args);
}
void logerror(const char *format, ...)
{
va_list args;
va_start(args, format);
char *prefix = "Error: ";
char *tmp = alloca(strlen(format) + strlen(prefix) + 1);
strcpy(tmp, prefix);
strcat(tmp, format);
vfprintf(stderr, tmp, args);
fflush(stderr);
va_end(args);
}
void watchqueue_add_path(const char *pathname)
{
*watchlist = xmalloc(sizeof(struct watchlistentry));
struct watchlistentry *e = *watchlist;
char *path = xrealpath(pathname, NULL);
e->ifd = 0;
e->path = path;
e->isdir = path_is_directory(pathname);
e->next = NULL;
watchlist = &e->next;
}
void create_watches(int fd, uint32_t mask)
{
for(struct watchlistentry *lkp = watchlist_head; lkp != NULL; lkp = lkp->next)
{
int ret = inotify_add_watch(fd, lkp->path, mask);
if(ret == -1)
{
perror("inotify_add_watch");
exit(EXIT_FAILURE);
}
lkp->ifd = ret;
}
}
bool redirect_stdout(const char *outfile)
{
int fd = open(outfile, O_CREAT | O_WRONLY | O_APPEND, S_IRUSR | S_IWUSR);
if(fd == -1)
{
perror("open");
return false;
}
if(dup2(fd, 1) == -1 || dup2(fd, 2) == -1)
{
perror("dup2");
return false;
}
return true;
}
const char *mask_to_names(int mask)
{
static char ret[1024];
size_t n = sizeof(ret) - 1;
if(mask & IN_ATTRIB)
{
strncat(ret, "IN_ATTRIB,", n);
}
if(mask & IN_OPEN)
{
strncat(ret, "IN_OPEN,", n);
}
if(mask & IN_CLOSE)
{
strncat(ret, "IN_CLOSE,", n);
}
if(mask & IN_CLOSE_NOWRITE)
{
strncat(ret, "IN_CLOSE,", n);
}
if(mask & IN_CLOSE_WRITE)
{
strncat(ret, "IN_CLOSE_WRITE,", n);
}
if(mask & IN_CREATE)
{
strncat(ret, "IN_CREATE,", n);
}
if(mask & IN_DELETE)
{
strncat(ret, "IN_DELETE,", n);
}
if(mask & IN_DELETE_SELF)
{
strncat(ret, "IN_DELETE_SELF,", n);
}
if(mask & IN_MODIFY)
{
strncat(ret, "IN_MODIFY,", n);
}
if(mask & IN_MOVE)
{
strncat(ret, "IN_MOVE,", n);
}
if(mask & IN_MOVE_SELF)
{
strncat(ret, "IN_MOVE_SELF,", n);
}
if(mask & IN_MOVED_FROM)
{
strncat(ret, "IN_MOVED_FROM,", n);
}
if(mask & IN_MOVED_TO)
{
strncat(ret, "IN_MOVED_TO,", n);
}
for(int i = n; i >= 0; --i)
{
if(ret[i] == ',')
{
ret[i] = 0;
break;
}
}
ret[1023] = 0;
return ret;
}
bool run_prog(const char *eventfile, uint32_t eventmask)
{
pid_t pid = fork();
if(pid == 0)
{
if(path_logfile)
{
if(!redirect_stdout(path_logfile))
{
return false;
}
}
if(!noenv)
{
char envvar[30];
snprintf(envvar, sizeof(envvar), "ADHOCIFYEVENT=%" PRIu32, eventmask);
putenv(envvar);
}
for(unsigned int i = 0; i < n_script_arguments; i++)
{
char *argument = script_arguments[i];
if(argument != NULL)
{
if(STREQ(argument, SCRIPT_PLACE_SPECIFIER) || STREQ(argument, EVENTFILE_PLACEHOLDER))
{
script_arguments[i] = eventfile;
}
if(STREQ(argument, EVENTSTR_PLACEHOLDER))
{
script_arguments[i] = mask_to_names(eventmask);
}
}
}
execvp(prog, script_arguments);
logerror("Exec of %s failed: %s\n", prog, strerror(errno));
int exitcode = (errno == ENOENT) ? 127 : EXIT_FAILURE;
exit(exitcode);
}
if(pid == -1)
{
perror("fork");
return false;
}
return true;
}
uint32_t name_to_mask(const char *name)
{
if(STREQ(name, "IN_CLOSE_WRITE"))
return IN_CLOSE_WRITE;
else if(STREQ(name, "IN_OPEN"))
return IN_OPEN;
else if(STREQ(name, "IN_MODIFY"))
return IN_MODIFY;
else if(STREQ(name, "IN_DELETE"))
return IN_DELETE;
else if(STREQ(name, "IN_ATTRIB"))
return IN_ATTRIB;
else if(STREQ(name, "IN_CLOSE_NOWRITE"))
return IN_CLOSE_NOWRITE;
else if(STREQ(name, "IN_MOVED_FROM"))
return IN_MOVED_FROM;
else if(STREQ(name, "IN_MOVED_TO"))
return IN_MOVED_TO;
else if(STREQ(name, "IN_CREATE"))
return IN_CREATE;
else if(STREQ(name, "IN_DELETE_SELF"))
return IN_DELETE_SELF;
else if(STREQ(name, "IN_MOVE_SELF"))
return IN_MOVE_SELF;
else if(STREQ(name, "IN_ALL_EVENTS"))
return IN_ALL_EVENTS;
else if(STREQ(name, "IN_CLOSE"))
return IN_CLOSE;
else if(STREQ(name, "IN_MOVE"))
return IN_MOVE;
else
return 0;
}
void check_forkbomb(const char *path_logfile, const char *path_prog)
{
char *dir_log = ndirname(path_logfile);
char *dir_prog = ndirname(path_prog);
struct watchlistentry *lkp = watchlist_head;
while(lkp)
{
if(lkp->isdir)
{
char *dir_lkpPath = lkp->path;
if(STREQ(dir_lkpPath, dir_log) || STREQ(dir_lkpPath, dir_prog))
{
logerror("Don't place your logfiles or command in a directory you are watching for events. Pass -b to "
"bypass this check.\n");
exit(EXIT_FAILURE);
}
}
lkp = lkp->next;
}
free(dir_log);
free(dir_prog);
}
void queue_watches_from_stdin()
{
char *line = NULL;
size_t n = 0;
ssize_t r;
while((r = getline(&line, &n, stdin)) != -1)
{
if(line[r - 1] == '\n')
line[r - 1] = 0;
watchqueue_add_path(line);
}
}
char *get_eventfile_abspath(struct inotify_event *event)
{
char *wdpath = find_ifd_path(event->wd);
if(wdpath == NULL)
{
return NULL;
}
char *result = NULL;
if((event->len) > 0)
{
if(asprintf(&result, "%s/%s", wdpath, event->name) == -1)
{
return NULL;
}
}
else
{
result = strdup(wdpath);
}
return result;
}
void handle_event(struct inotify_event *event)
{
if(event->mask & mask)
{
char *eventfile_abspath = get_eventfile_abspath(event);
if(eventfile_abspath == NULL)
{
logerror("Could not get absolute path for event. Watch descriptor %i\n", event->wd);
exit(EXIT_FAILURE);
}
if(is_ignored(eventfile_abspath))
{
free(eventfile_abspath);
return;
}
logwrite("Starting execution of command %s\n", prog);
bool r = run_prog(eventfile_abspath, event->mask);
if(!r)
{
logerror("Execution of command %s failed\n", prog);
exit(EXIT_FAILURE);
}
fflush(stdout);
fflush(stderr);
free(eventfile_abspath);
}
}
static inline char *get_cwd()
{
return getcwd(NULL, 0);
}
void print_usage()
{
printf("adhocify [OPTIONS] command [arguments for command] - Monitor for inotify events and launch commands\n\n");
printf("--daemon, -d run as a daemon\n");
printf("--path, -w adds the specified path to the watchlist\n");
printf("--logfile, -o path to write output of adhocify and stdout/stderr of launched commands to\n");
printf("--mask, -m inotify event to watch for (see inotify(7)). Can be specified multiple times to "
"watch for several events\n");
printf("--no-env, -a if specified, the inotify event which occured won't be passed to the command as an "
"environment variable\n");
printf("--silent, -q surpress any output created by adhocify itself\n");
printf("--stdin, -s Read the paths which must be added to the watchlist from stdin. Each path must be "
"in a seperate line\n");
printf("--no-forkbomb-check, -b Disable fork bomb detection\n");
printf("--ignore, -i Shell wildcard pattern (see glob(7)) to ignore events on files for which the "
"pattern matches\n");
printf("--exit-with-child, -e Exit when the commands exits. You can also specify a return code (e. g. -e=1 to "
"exit only on errors)\n");
printf("\nIf your command should know the file the event occured on, use the {} placeholder when you specify the "
"arguments (like xargs)\n");
}
static struct option long_options[] = {{"daemon", no_argument, 0, 'd'},
{"logfile", required_argument, 0, 'o'},
{"mask", required_argument, 0, 'm'},
{"path", required_argument, 0, 'w'},
{"no-env", no_argument, 0, 'a'},
{"stdin", no_argument, 0, 's'},
{"no-forkbomb-check", no_argument, 0, 'b'},
{"ignore", required_argument, 0, 'i'},
{"silent", no_argument, 0, 'q'},
{"help", no_argument, 0, 'h'},
{"exit-with-child", optional_argument, 0, 'e'}};
// fills global n_script_arguments and script_arguments var
void fill_script_arguments(size_t n_args, char *args[])
{
n_script_arguments = n_args + 2; // 2 = argv0 and terminating NULL
char **arguments = xmalloc(n_script_arguments * sizeof(char *));
const char *argv0 = memrchr(prog, '/', strlen(prog));
argv0 = (argv0 == NULL) ? prog : argv0 + 1;
arguments[0] = argv0;
const int begin_offset = 1;
for(unsigned int i = 0; i < n_args; i++)
{
char *argument = args[i];
arguments[i + begin_offset] = strdup(argument);
}
arguments[n_args + begin_offset] = NULL;
script_arguments = arguments;
}
void parse_options(int argc, char **argv)
{
char *watchpath = NULL;
int option;
int option_index;
uint32_t optmask = 0;
while((option = getopt_long(argc, argv, "absdo:w:m:l:i:e::", long_options, &option_index)) != -1)
{
switch(option)
{
case 'd':
daemonize = true;
break;
case 'o':
path_logfile = optarg;
break;
case 'm':
optmask = name_to_mask(optarg);
if(optmask == 0)
{
logerror("Not supported inotify event: %s\n", optarg);
exit(EXIT_FAILURE);
}
mask |= optmask;
break;
case 'w':
watchpath = optarg;
watchqueue_add_path(watchpath);
break;
case 'a':
noenv = true;
break;
case 's':
fromstdin = true;
break;
case 'b':
forkbombcheck = false;
break;
case 'i':
add_to_ignore_list(optarg);
break;
case 'q':
silent = true;
break;
case 'h':
print_usage();
exit(EXIT_SUCCESS);
case 'e':
exit_with_child = true;
if(optarg)
{
if(*optarg == '!')
{
negate_child_exit_code = true;
++optarg;
}
if(*optarg == '\0')
{
logerror("Please specify the exit code\n");
exit(EXIT_FAILURE);
}
awaited_child_exit_code = atoi(optarg);
}
break;
}
}
if(optind == argc)
{
print_usage();
logerror("missing command path\n");
exit(EXIT_FAILURE);
}
prog = argv[optind++];
if(optind <= argc)
{
fill_script_arguments(argc - optind, &argv[optind]);
}
}
void process_options()
{
if(fromstdin)
{
queue_watches_from_stdin();
}
if(watchlist_head == NULL)
{
watchqueue_add_path(get_cwd());
}
if(mask == 0)
{
mask |= IN_CLOSE_WRITE;
}
if(path_logfile)
{
path_logfile = xrealpath(path_logfile, NULL);
}
if(forkbombcheck)
{
char *path_prog = realpath(prog, NULL);
if(path_prog != NULL)
{
check_forkbomb(path_logfile, path_prog);
}
free(path_prog);
}
if(daemonize)
{
if(daemon(0, 0) == -1)
{
perror("daemon");
exit(EXIT_FAILURE);
}
}
}
void start_monitoring(int ifd)
{
while(1)
{
int len;
int offset = 0;
char buf[BUF_SIZE];
len = read(ifd, buf, BUF_SIZE);
if(len == -1)
{
if(errno == EINTR)
continue;
perror("read");
exit(EXIT_FAILURE);
}
while(offset < len)
{
struct inotify_event *event = (struct inotify_event *)&buf[offset];
handle_event(event);
offset += sizeof(struct inotify_event) + event->len;
}
}
}
void child_handler(int signum, siginfo_t *info, void *context)
{
if(signum != SIGCHLD)
{
return;
}
int status;
pid_t p = waitpid(-1, &status, WNOHANG);
if(p == -1)
{
logerror("waitpid failed when handling child exit\n");
exit(EXIT_FAILURE);
}
int adhocify_exit_code = 0;
if(WIFEXITED(status))
{
adhocify_exit_code = WEXITSTATUS(status);
if(adhocify_exit_code == 127)
{
logwrite("command not found, exiting\n");
exit(adhocify_exit_code);
}
if(exit_with_child && awaited_child_exit_code > -1)
{
bool must_exit = adhocify_exit_code == awaited_child_exit_code;
if(negate_child_exit_code)
{
must_exit = !must_exit;
}
if(must_exit)
{
logwrite("command exited with specified exit code, exiting too\n");
exit(adhocify_exit_code);
}
}
}
if(exit_with_child && WIFSIGNALED(status))
{
adhocify_exit_code = 128 + WTERMSIG(status); // copy bash's behaviour
exit(adhocify_exit_code);
}
}
void set_signals()
{
struct sigaction action;
action.sa_flags = SA_NOCLDSTOP | SA_SIGINFO;
action.sa_sigaction = &child_handler;
if(sigaction(SIGCHLD, &action, NULL) == -1)
{
logerror("Error when setting up the signal handler\n");
exit(EXIT_FAILURE);
}
}
int main(int argc, char **argv)
{
if(argc < 2)
{
print_usage();
exit(EXIT_FAILURE);
}
// signal(SIGCHLD, SIG_IGN);
set_signals();
parse_options(argc, argv);
process_options();
int ifd = inotify_init();
if(ifd == -1)
{
perror("inotify_init");
exit(EXIT_FAILURE);
}
create_watches(ifd, mask);
start_monitoring(ifd);
}