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<TITLE>Process Monitor HOW-TO for Linux: File procautostart.cpp</TITLE>
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<H2><A NAME="s3">3. File procautostart.cpp</A></H2>
<P>//Dal vostro browser salvate questo file come un <B>file di testo</B> e chiamatelo "procautostart.cpp".
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// Author: Al Dev alavoor@yahoo.com
//
// Program to monitor the unix processes
// and automatically re-start them if they die
//
//************************************************************************
// NOTE: This program uses the Al Dev's String class library. Download string
// class from http://linuxdoc.org/HOWTO/C++Programming-HOWTO.html
//************************************************************************
#include <stdio.h>
#include <strings.h> // C strings
#include <unistd.h> // for getopt
#include <alloc.h> // for free
#include <errno.h> // for kill() - error numbers command
extern int errno;
#ifdef Linux
#include <asm/errno.h> // for kill() - error numbers command
#endif
#include <sys/types.h> // for kill() command
#include <signal.h> // for kill() command
#include <sys/wait.h> // for wait()
#include <stdlib.h> // for setenv()
#include <time.h> // for strftime()
#include <libgen.h> // for basename()
//#include <syslog.h> // for logging
#include "debug.h"
#include "String.h"
#include "StringTokenizer.h"
#define BUFF_HUN 100
#define BUFF_THOU 1024
#define PR_INIT_VAL -10
#define WAIT_FOR_SYS 5 // wait for process to start up
#define DEF_SL_SECS 6 // default sleep time
#define SAFE_MEM 10 // to avoid any possible memory leaks
#define LOG_NO false // do not output to logfile
#define LOG_YES true // do output to logfile
#define STD_ERR_NO false // do not print to std err
#define STD_ERR_YES true // do print to std err
#define DATE_NO false // do not print date
#define DATE_YES true // do print date
int start_process(char *commandline, char *args[], char **envp, pid_t proc_pid);
int fork2(pid_t parent_pid, unsigned long tsecs);
inline void error_msg(char *mesg_out, char *lg_file, bool pr_lg, bool std_err, bool pr_dt);
//////////////////////////////////////////////
// To test this program use --
// procautostart -n 5 -c 'monitor_test dummy1 -a dummy2 -b dummy3 ' &
//////////////////////////////////////////////
void usage(char **argv)
{
printf("%s:\n", argv[0]);
printf("\ninterval specification:\n");
printf(" -n # -- seconds\n");
printf(" -m # -- microseconds\n");
printf(" -o # -- nanoseconds\n");
printf("\nprocess specification:\n");
printf(" -c 'cmdline'\n");
printf
(" -p pidfile -- if specified reads process pid from this file\n");
printf("\n");
printf("\nUsage : %s -n <seconds> -m <microsecond> -o <nanosecond> -c '<command>'\n", argv[0]);
printf("\nExample: procautostart -n 5 -c 'monitor_test dummy1 -a dummy2 -b dummy3 ' \n");
exit(-1);
}
int main(int argc, char **argv, char **envp)
{
unsigned long sleep_sec, sleep_micro, sleep_nano;
int ch;
pid_t proc_pid;
int pr_no = PR_INIT_VAL;
char mon_log[40];
char *pr_name = NULL, **cmdargs = NULL;
String cmdline;
char *pidfile = NULL;
// you can turn on debug by editing Makefile and put -DDEBUG_PRT in gcc
debug_("test debug", "this line");
debug_("argc", argc);
// Use getpid() - man 2 getpid()
proc_pid = getpid(); // get the Process ID of procautostart
debug_("PID proc_pid", (int) proc_pid);
// Create directory to hold log, temp files
system("mkdir mon 1>/dev/null 2>/dev/null");
sleep_sec = DEF_SL_SECS ; // default sleep time
sleep_micro = 0; // default micro-sleep time
sleep_nano = 0; // default nano-sleep time
optarg = NULL;
while ((ch = getopt(argc, argv, "n:m:o:h:c:")) != -1) // needs trailing colon :
{
switch (ch)
{
case 'n':
debug_("scanned option n ", optarg);
sleep_sec = atoi(optarg);
debug_("sleep_sec", sleep_sec);
break;
case 'm':
debug_("scanned option m ", optarg);
sleep_micro = atoi(optarg);
debug_("sleep_micro", sleep_micro);
break;
case 'o':
debug_("scanned option o ", optarg);
sleep_nano = atoi(optarg);
debug_("sleep_nano", sleep_nano);
break;
case 'c':
debug_("scanned option c ", optarg);
cmdline = optarg;
//cmdline = strdup(optarg); // does auto-malloc here
debug_("cmdline", cmdline.val());
break;
case 'h':
debug_("scanned option h ", optarg);
usage(argv);
break;
case 'p':
pidfile = strdup(optarg);
break;
default:
debug_("ch", "default");
usage(argv);
break;
}
}
if (cmdline.length() == 0) //if (cmdline == NULL)
usage(argv);
// detach from the main process
if (fork()) // 0 returned in child process
exit(0); // exit parent process - non-zero child PID got here...
//openlog(argv[0], LOG_PID, LOG_DAEMON);
// trim the trailing blanks -- otherwise problem in grep command
//cmdline.trim(true);
//cmdline.chopall('&'); // trim trailing ampersand
debug_("cmdline", cmdline.val());
// Start the process
{
// Find the command line args
StringTokenizer strtokens(cmdline.val()); // string tokenizer is borrowed from Java
cmdargs = (char **) calloc(strtokens.countTokens() + SAFE_MEM, sizeof(char *));
debug_("countTokens()", strtokens.countTokens());
for (int tmpii = 0; strtokens.hasMoreTokens(); tmpii++)
{
cmdargs[tmpii] = strdup(strtokens.nextToken().val());
debug_("tmpii", tmpii);
debug_("cmdargs[tmpii]", (char *) cmdargs[tmpii]);
}
// In case execve you MUST NOT have trailing ampersand & in the command line!!
//pr_no = start_process(cmdline, NULL, NULL, proc_pid); // Using execlp ...
pr_no = start_process(cmdargs[0], & cmdargs[0], envp, proc_pid); // Using execve ....
//cmdpid = start_command(cmdargs, envp, pidfile);
// You can also use syslog if you do not like above logging
//syslog(LOG_NOTICE, "Started process: %s", cmdline.val());
debug_("The child pid", pr_no);
if (pr_no < 0)
{
fprintf(stderr, "\nFatal Error: Failed to start the process\n");
exit(-1);
}
sleep(WAIT_FOR_SYS); // wait for the process to come up
// Get process name - only the first word from cmdline
pr_name = strdup(basename(cmdargs[0])); // process name, does auto-malloc here
}
// generate log file names
{
char aa[21];
strncpy(aa, pr_name, 20); aa[20] = '\0';
// Define mon file-names - make it unique with combination of
// process name and process id
sprintf(mon_log, "mon/%s%d.log", aa, (int) proc_pid);
}
// Print out pid to log file
if (pr_no > 0)
{
char aa[200];
sprintf(aa, "Process ID of %s is %d", pr_name, pr_no);
error_msg(aa, mon_log, LOG_YES, STD_ERR_NO, DATE_YES);
}
// monitors the process - restarts if process dies...
char print_log[200];
while (1) // infinite loop - monitor every 6 seconds
{
//debug_("Monitoring the process now...", ".");
switch (kill(pr_no, 0))
{
case 0:
break;
default:
case ESRCH: // process died !!
// ERSRCH means - No process can be found corresponding to pr_no
// hence process had died !!
sprintf(print_log, "Error ESRCH: No process or process group can be found for %d", pr_no);
error_msg(print_log, mon_log, LOG_YES, STD_ERR_YES, DATE_YES);
// You can also use syslog if you do not like above logging
//syslog(LOG_NOTICE, "PROCESS DIED: %s", cmdline.val());
//pr_no = start_process(cmdline, NULL, NULL, proc_pid); // Using execlp ....
pr_no = start_process(cmdargs[0], & cmdargs[0], envp, proc_pid); // Using execve ....
// You can also use syslog if you do not like below logging
//syslog(LOG_NOTICE, "Started process: %s", cmdline.val());
sprintf(print_log, "Starting process %s", pr_name);
error_msg(print_log, mon_log, LOG_YES, STD_ERR_NO, DATE_NO);
sleep(WAIT_FOR_SYS); // wait for the process to come up
break;
}
sprintf(print_log, "Process ID of %s is %d", pr_name, pr_no);
error_msg(print_log, mon_log, LOG_YES, STD_ERR_NO, DATE_NO);
//debug_("Sleeping now ......", ".");
sleep(sleep_sec);
// Uncomment these to use micro-seconds
// For real-time process control use micro-seconds or nana-seconds sleep functions
// See 'man3 usleep', 'man 2 nanasleep'
// If you do not have usleep() or nanosleep() on your system, use select() or poll()
// specifying no file descriptors to test.
//usleep(sleep_micro);
// To sleep nano-seconds ... Uncomment these to use nano-seconds
//struct timespec *req = new struct timespec;
//req->tv_sec = 0; // seconds
//req->tv_nsec = sleep_nano; // nanoseconds
//nanosleep( (const struct timespec *)req, NULL);
/* You can use select instead of sleep for portability
struct timeval interval;
interval.tv_sec += tmp;
interval.tv_usec += (long int) 1e3 *tmp;
select(1, NULL, NULL, NULL, & interval);
*/
}
//closelog(); if using syslog
}
inline void error_msg(char *mesg_out, char *lg_file, bool pr_lg, bool std_err, bool pr_dt)
{
if (pr_lg) // (pr_lg == true) output to log file
{
char tmp_msg[BUFF_THOU];
if (pr_dt == true) // print date and message to log file 'lg_file'
{
sprintf(tmp_msg, "date >> %s; echo '\n%s\n' >> %s\n ",
lg_file, mesg_out, lg_file);
system(tmp_msg);
}
else
{
sprintf(tmp_msg, "echo '\n%s\n' >> %s\n ",
mesg_out, lg_file);
system(tmp_msg);
}
}
if (std_err) // (std_err == true) output to standard error
fprintf(stderr, "\n%s\n", mesg_out);
//debug_("mesg_out", mesg_out);
}
// start a process and returns PID or -ve value if error
// The main() function has envp arg as in - main(int argc, char *argv[], char **envp)
int start_process(char *commandline, char *args[], char **envp, pid_t parent_pid)
{
int ff;
unsigned long tsecs;
tsecs = time(NULL); // time in secs since Epoch 1 Jan 1970
debug_("Time tsecs", tsecs);
// Use fork2() instead of fork to avoid zombie child processes
switch (ff = fork2(parent_pid, tsecs)) // fork creates 2 process each executing the following lines
{
case -1:
fprintf(stderr, "\nFatal Error: start_process() - Unable to fork process\n");
_exit(errno);
break;
case 0: // child process
debug_("\nStarting the start child process\n", " ");
// For child process to ignore the interrupts (i.e. to put
// child process in "background" mode.
// Signals are sent to all processes started from a
// particular terminal. Accordingly, when a program is to be run non-interactively
// (started by &), the shell arranges that the program will ignore interrupts, so
// it won't be stopped by interrupts intended for foreground processes.
// Hence if previous value of signal is not IGN than set it to IGN.
// Note: Signal handlers cannot be set for SIGKILL, SIGSTOP
if (signal(SIGINT, SIG_IGN) == SIG_ERR)
fprintf(stderr, "\nSignal Error: Not able to set signal to SIGINT\n");
else
if (signal(SIGINT, SIG_IGN) != SIG_IGN) // program already run in background
signal(SIGINT, SIG_IGN); // ignore interrupts
if (signal(SIGHUP, SIG_IGN) == SIG_ERR)
fprintf(stderr, "\nSignal Error: Not able to set signal to SIGHUP\n");
else
if (signal(SIGHUP, SIG_IGN) != SIG_IGN) // program already run in background
signal(SIGHUP, SIG_IGN); // ignore hangups
if (signal(SIGQUIT, SIG_IGN) == SIG_ERR)
fprintf(stderr, "\nSignal Error: Not able to set signal to SIGQUIT\n");
else
if (signal(SIGQUIT, SIG_IGN) != SIG_IGN) // program already run in background
signal(SIGQUIT, SIG_IGN); // ignore Quit
if (signal(SIGABRT, SIG_IGN) == SIG_ERR)
fprintf(stderr, "\nSignal Error: Not able to set signal to SIGABRT\n");
else
if (signal(SIGABRT, SIG_IGN) != SIG_IGN) // program already run in background
signal(SIGABRT, SIG_IGN); // ignore ABRT
if (signal(SIGTERM, SIG_IGN) == SIG_ERR)
fprintf(stderr, "\nSignal Error: Not able to set signal to SIGTERM\n");
else
if (signal(SIGTERM, SIG_IGN) != SIG_IGN) // program already run in background
signal(SIGTERM, SIG_IGN); // ignore TERM
// sigtstp - Stop typed at tty. Ignore this so that parent process
// be put in background with CTRL+Z or with SIGSTOP
if (signal(SIGTSTP, SIG_IGN) == SIG_ERR)
fprintf(stderr, "\nSignal Error: Not able to set signal to SIGTSTP\n");
else
if (signal(SIGTSTP, SIG_IGN) != SIG_IGN) // program already run in background
signal(SIGTSTP, SIG_IGN); // ignore TSTP
// You can use debug_ generously because they do NOT increase program size!
debug_("before execve commandline", commandline);
debug_("before execve args[0]", args[0]);
debug_("before execve args[1]", args[1]);
debug_("before execve args[2]", args[2]);
debug_("before execve args[3]", args[3]);
debug_("before execve args[4]", args[4]);
debug_("before execve args[5]", args[5]);
debug_("before execve args[6]", args[6]);
debug_("before execve args[7]", args[7]);
debug_("before execve args[8]", args[8]);
debug_("before execve args[9]", args[9]);
execve(commandline, args, envp);
// execlp, execvp does not provide expansion of metacharacters
// like <, >, *, quotes, etc., in argument list. Invoke
// the shell /bin/sh which then does all the work. Construct
// a string 'commandline' that contains the complete command
//execlp("/bin/sh", "sh", "-c", commandline, (char *) 0); // if success than NEVER returns !!
// If execlp returns than there is some serious error !! And
// executes the following lines below...
fprintf(stderr, "\nFatal Error: Unable to start child process\n");
ff = -2;
exit(127);
break;
default: // parent process
// child pid is ff;
if (ff < 0)
fprintf(stderr, "\nFatal Error: Problem while starting child process\n");
{
char buff[BUFF_HUN];
FILE *fp1;
sprintf(buff, "mon/%d%lu.out", (int) parent_pid, tsecs); // tsecs is unsigned long
fp1 = fopen(buff, "r");
if (fp1 != NULL)
{
buff[0] = '\0';
fgets(buff, BUFF_HUN, fp1);
ff = atoi(buff);
}
fclose(fp1);
debug_("start process(): ff - ", ff);
#ifndef DEBUG_PRT
sprintf(buff, "rm -f mon/%d%lu.out", (int) parent_pid, tsecs);
system(buff);
#endif // DEBUG_PRT
}
// define wait() to put child process in foreground or else put in background
//waitpid(ff, & status, WNOHANG || WUNTRACED);
//waitpid(ff, & status, WUNTRACED);
//wait(& status);
break;
}
return ff;
}
/* fork2() -- like fork, but the new process is immediately orphaned
* (won't leave a zombie when it exits)
* Returns 1 to the parent, not any meaningful pid.
* The parent cannot wait() for the new process (it's unrelated).
*/
/* This version assumes that you *haven't* caught or ignored SIGCHLD. */
/* If you have, then you should just be using fork() instead anyway. */
int fork2(pid_t parent_pid, unsigned long tsecs)
{
pid_t mainpid, child_pid = -10;
int status;
char buff[BUFF_HUN];
if (!(mainpid = fork()))
{
switch (child_pid = fork())
{
case 0:
//child_pid = getpid();
//debug_("At case 0 fork2 child_pid : ", child_pid);
return 0;
case -1:
_exit(errno); /* assumes all errnos are <256 */
default:
debug_("fork2 child_pid : ", (int) child_pid);
sprintf(buff, "echo %d > mon/%d%lu.out", (int) child_pid, (int) parent_pid, tsecs);
system(buff);
_exit(0);
}
}
//debug_("fork2 pid : ", pid);
if (mainpid < 0 || waitpid(mainpid, & status, 0) < 0)
return -1;
if (WIFEXITED(status))
if (WEXITSTATUS(status) == 0)
return 1;
else
errno = WEXITSTATUS(status);
else
errno = EINTR; /* well, sort of :-) */
return -1;
}
//
// char respawn[1024];
// strcpy(respawn, cmdline);
// For "C" program use kill(pid_t process, int signal) function.
// #include <signal.h> // See 'man 2 kill'
// Returns 0 on success and -1 with errno set.
// kill -0 $pid 2>/dev/null || respawn
// To get the exit return status do --
// kill -0 $pid 2>/dev/null | echo $?
// Return value 0 is success and others mean failure
// Sending 0 does not do anything to target process, but it tests
// whether the process exists. The kill command will set its exit
// status based on this process.
//
// Alternatively, you can use
// ps -p $pid >/dev/null 2>&1 || respawn
// To get the exit return status do --
// ps -p $pid >/dev/null 2>&1 | echo $?
// Return value 0 is success and others mean failure
//***********************************************************************
// You can use pidfile to get the process id
//**********************************************************************
/*
void poll_pidfile(char *pidfile)
{
struct stat buf;
struct timeval interval =
{
tv_sec:0, tv_usec:(long int) 1e4
}; // 10 miliseconds
while (stat(pidfile, & buf) ? errno == ENOENT : buf.st_size == 0)
{
struct timeval i = interval;
select(1, NULL, NULL, NULL, & i);
}
}
int start_command(char **args, char **envp, char *pidfile)
{
pid_t cmdpid;
if (pidfile != NULL)
{
switch (unlink(pidfile))
{
case ENOENT:
case 0:
break;
default:
return -1;
}
}
switch (cmdpid = fork2())
{
case 0: // child
execve(args[0], args, envp);
exit(-1);
case -1: // error
return -1;
default: // parent
break;
}
if (pidfile != NULL)
{
FILE *pf;
poll_pidfile(pidfile);
if ((pf = fopen(pidfile, "r")) == NULL)
{
syslog(LOG_ERR, "failed to read pidfile, using fork2 pid");
}
else
{
char textpid[1024];
pid_t pid;
fgets(textpid, sizeof(textpid), pf);
if ((pid = atoi(textpid)) != -1)
{
cmdpid = pid;
} else
syslog(LOG_ERR,
"failed to find pid in pidfile, using fork2 pid");
fclose(pf);
}
}
return cmdpid;
}
*/
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