Add new option "-e" to pidstat, which can be used to pass a program

to execute and make pidstat monitor it.
When the program terminates, pidstat will catch the SIGCHLD signal and
display the average statistics.

Signed-off-by: Sebastien GODARD <sysstat@users.noreply.github.com>

diff --git a/pidstat.c b/pidstat.c
index c7181479d4c287c1c293b2ff271f6391ab319e2b..c512b474c8cfec0780084b4a261aa1a4c5ba75af 100644 (file)
--- a/pidstat.c
+++ b/pidstat.c
@@ -71,8 +71,8 @@ unsigned int pidflag = 0;     /* General flags */
 unsigned int tskflag = 0;      /* TASK/CHILD stats */
 unsigned int actflag = 0;      /* Activity flag */
 
-struct sigaction alrm_act, int_act;
-int sigint_caught = 0;
+struct sigaction alrm_act, int_act, chld_act;
+int signal_caught = 0;
 
 /*
  ***************************************************************************
@@ -84,7 +84,7 @@ int sigint_caught = 0;
  */
 void usage(char *progname)
 {
-       fprintf(stderr, _("Usage: %s [ options ] [ <interval> [ <count> ] ]\n"),
+       fprintf(stderr, _("Usage: %s [ options ] [ <interval> [ <count> ] ] [ -e <program> <args> ]\n"),
                progname);
 
        fprintf(stderr, _("Options are:\n"
@@ -109,15 +109,15 @@ void alarm_handler(int sig)
 
 /*
  ***************************************************************************
- * SIGINT signal handler.
+ * SIGINT and SIGCHLD signals handler.
  *
  * IN:
  * @sig        Signal number.
  ***************************************************************************
  */
-void int_handler(int sig)
+void sig_handler(int sig)
 {
-       sigint_caught = 1;
+       signal_caught = 1;
 }
 
 /*
@@ -2512,14 +2512,14 @@ void rw_pidstat_loop(int dis_hdr, int rows)
 
        /* Set a handler for SIGINT */
        memset(&int_act, 0, sizeof(int_act));
-       int_act.sa_handler = int_handler;
+       int_act.sa_handler = sig_handler;
        sigaction(SIGINT, &int_act, NULL);
 
        /* Wait for SIGALRM (or possibly SIGINT) signal */
        pause();
 
-       if (sigint_caught)
-               /* SIGINT signal caught during first interval: Exit immediately */
+       if (signal_caught)
+               /* SIGINT/SIGCHLD signals caught during first interval: Exit immediately */
                return;
 
        do {
@@ -2561,8 +2561,8 @@ void rw_pidstat_loop(int dis_hdr, int rows)
 
                        pause();
 
-                       if (sigint_caught) {
-                               /* SIGINT signal caught => Display average stats */
+                       if (signal_caught) {
+                               /* SIGINT/SIGCHLD signals caught => Display average stats */
                                count = 0;
                                printf("\n");   /* Skip "^C" displayed on screen */
                        }
@@ -2584,6 +2584,61 @@ void rw_pidstat_loop(int dis_hdr, int rows)
        }
 }
 
+/*
+ ***************************************************************************
+ * Start a program that will be monitored by pidstat.
+ *
+ * IN:
+ * @argc       Number of arguments.
+ * @argv       Arguments values.
+ *
+ * RETURNS:
+ * The PID of the program executed.
+ ***************************************************************************
+ */
+pid_t exec_pgm(int argc, char **argv)
+{
+       pid_t child;
+       char *args[argc + 1];
+       int i;
+
+       child = fork();
+
+       switch(child) {
+
+               case -1:
+                       perror("fork");
+                       exit(4);
+                       break;
+
+               case 0:
+                       /* Child */
+                       for (i = 0; i < argc; i++) {
+                               args[i] = argv[i];
+                       }
+                       args[argc] = NULL;
+
+                       execvp(args[0], args);
+                       perror("exec");
+                       exit(4);
+                       break;
+
+               default:
+                       /*
+                        * Parent.
+                        * Set a handler for SIGCHLD (signal that will be received
+                        * by pidstat when the child program terminates).
+                        * The handler is the same as for SIGINT: Stop and display
+                        * average statistics.
+                        */
+                       memset(&chld_act, 0, sizeof(chld_act));
+                       chld_act.sa_handler = sig_handler;
+                       sigaction(SIGCHLD, &chld_act, NULL);
+
+                       return child;
+       }
+}
+
 /*
  ***************************************************************************
  * Main entry to the pidstat program.
@@ -2620,7 +2675,16 @@ int main(int argc, char **argv)
        /* Process args... */
        while (opt < argc) {
 
-               if (!strcmp(argv[opt], "-p")) {
+               if (!strcmp(argv[opt], "-e")) {
+                       if (!argv[++opt]) {
+                               usage(argv[0]);
+                       }
+                       pidflag |= P_D_PID;
+                       update_pid_array(&pid_array_nr, exec_pgm(argc - opt, argv + opt));
+                       break;
+               }
+
+               else if (!strcmp(argv[opt], "-p")) {
                        pidflag |= P_D_PID;
                        if (argv[++opt]) {