Add -P option for PID file

Fixes hoytech#60

vmtouch.c

@@ -69,6 +69,7 @@ THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <stdarg.h>
 #include <stdint.h>
 #include <time.h>
+#include <signal.h>
 #include <sys/select.h>
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -136,6 +137,7 @@ int o_ignorehardlinkeduplictes=0;
 size_t o_max_file_size=SIZE_MAX;
 int o_wait=0;
 static char *o_batch = NULL;
+static char *o_pidfile = NULL;
 int o_0_delim = 0;
 
 
@@ -177,6 +179,7 @@ void usage() {
   printf("  -b <list file> get files or directories from the list file\n");
   printf("  -0 in batch mode (-b) separate paths with NUL byte instead of newline\n");
   printf("  -w wait until all pages are locked (only useful together with -d)\n");
+  printf("  -P <pidfile> write a pidfile (only working together with -l or -L)\n");
   printf("  -v verbose\n");
   printf("  -q quiet\n");
   exit(1);
@@ -858,7 +861,48 @@ static void vmtouch_batch_crawl(const char *path) {
   fclose(f);
 }
 
+static void remove_pidfile() {
+  int res = 0;
 
+  res = unlink(o_pidfile);
+  if (res < 0 && errno != ENOENT) {
+    warning("unable to remove pidfile %s (%s)", o_pidfile, strerror(errno));
+  }
+}
+
+static void write_pidfile() {
+  FILE *f = NULL;
+  size_t wrote = 0;
+
+  f = fopen(o_pidfile, "w");
+  if (!f) {
+    warning("unable to open %s (%s), skipping", o_pidfile, strerror(errno));
+    return;
+  }
+
+  wrote = fprintf(f, "%d\n", getpid());
+
+  fclose(f);
+
+  if (wrote < 0) {
+    warning("unable to write pidfile to %s (%s), delete it", o_pidfile, strerror(errno));
+    remove_pidfile();
+  }
+}
+
+static void signal_handler_clear_pidfile(int signal_num) {
+  remove_pidfile();
+}
+
+static void register_signals_for_pidfile() {
+  struct sigaction sa = {0};
+  sa.sa_handler = signal_handler_clear_pidfile;
+  if (sigaction(SIGINT, &sa, NULL) < 0 ||
+      sigaction(SIGTERM, &sa, NULL) < 0 ||
+      sigaction(SIGQUIT, &sa, NULL) < 0) {
+    warning("unable to register signals for pidfile (%s), skipping", strerror(errno));
+  }
+}
 
 
 
@@ -876,7 +920,7 @@ int main(int argc, char **argv) {
 
   pagesize = sysconf(_SC_PAGESIZE);
 
-  while((ch = getopt(argc, argv,"tevqlLdfFh0i:I:p:b:m:w")) != -1) {
+  while((ch = getopt(argc, argv, "tevqlLdfFh0i:I:p:b:m:P:w")) != -1) {
     switch(ch) {
       case '?': usage(); break;
       case 't': o_touch = 1; break;
@@ -903,6 +947,7 @@ int main(int argc, char **argv) {
       case 'w': o_wait = 1; break;
       case 'b': o_batch = optarg; break;
       case '0': o_0_delim = 1; break;
+      case 'P': o_pidfile = optarg; break;
     }
   }
 
@@ -931,6 +976,8 @@ int main(int argc, char **argv) {
 
   if (o_quiet && o_verbose) fatal("invalid option combination: -q and -v");
 
+  if (o_pidfile && (!o_lock && !o_lockall)) fatal("pidfile will only be created when -l or -L is specified");
+
   if (!argc && !o_batch) {
     printf("%s: no files or directories specified\n", prog);
     usage();
@@ -955,6 +1002,11 @@ int main(int argc, char **argv) {
         fatal("unable to mlockall (%s)", strerror(errno));
     }
 
+    if (o_pidfile) {
+      register_signals_for_pidfile();
+      write_pidfile();
+    }
+
     if (!o_quiet) printf("LOCKED %" PRId64 " pages (%s)\n", total_pages, pretty_print_size(total_pages*pagesize));
 
     if (o_wait) reopen_all();

vmtouch.pod

@@ -80,6 +80,10 @@ The list of files/directories to crawl is read from the specified list file, whi
 
 If -b ("batch mode") is in effect, assume the list file is delimited with NUL bytes instead of newlines, for example the output from find -print0. This is useful in case your filenames contain newline characters themselves.
 
+=item -P <pidfile>
+
+Create a PID file. This option is only working with -l or -L. The PID file will be automatically deleted when vmtouch got termination signals (SIGINT, SIGTERM, SIGQUIT) and leave.
+
 =item -v
 
 Verbose mode. While crawling, print out every file being processed along with its total number of pages and the number of its pages that are currently resident in memory to standard output.