Re: [Bug-wget] Timeouts too long?

[Paul McFerrin]

I've written a small & nifty program that will terminate a command line 
after N seconds.  It was written nearly 18 years ago and has served me 
very well.  I'm not saying that you always live with bad program design, 
but having a solution is quite nice.  The usage is:
    tcmd [-s {sig#}] [-t secs] [-x] cmd args ...

Ejoy.  This one is on me.

Here is the source, compile for yourselves.
----------------------------------------------------------------
#ident  "@(#)tcmd.c - NCP 1.1  08/28/91  -  PEM"

/*
       Execute the command line and terminate if it does
       not complete within a specified time limit.

       Usage:
               tcmd [-s signal] [-t secs] [-x] cmd args ...

       Upon timeout, signal "signal" (default is SIGTERM) is
       sent to all children in child process group.

       Exit codes:
                 0 = success
               254 = timed-out
               253 = execvp() failed for cmd
               252 = fork() failed
               251 = usage() exit
               128-146 = cmd terminated with signal 'sig - 127'
               all_others = exit status of "cmd"

       Author: Paul E. McFerrin, 55821, Aug 27, 1991

*/


#include <stdio.h>
#include <signal.h>
#include <errno.h>

extern int errno, optind;
extern char *optarg;
int     tlimit;         /* allowed time limit */
int     ksig;           /* signal to use to terminate */
int     timeout();      /* alarm clock signal catcher */
int     timedout;       /* > 0 if execution timed out */
int     childpid;       /* pid of chil process */
char    *cmd;           /* the name of our process, argv[0] */

main( argc, argv )
int     argc;
char    *argv[];
{
       int     xflag, opt, i, status, ws, myuid;

       myuid = getuid();       /* remember our real-uid */
       cmd = *argv;            /* save our name is global area */
       tlimit = 30;    /* default 30 seconds */
       ksig = SIGTERM; /* default terminate signal */
       xflag=0;
       timedout = 0;
       if( argc <= 1 ) usage();        /* no return */

       while ( (opt = getopt(argc, argv, "s:t:x")) != EOF ) {
               switch (opt) {
               case 'x' :
                       xflag = 1;
                       break;
               case 't' :
                       tlimit = atoi(optarg);
                       if( tlimit <= 0) {
                               fprintf(stderr, "%s: time limit must be 
> 0\n",
                                       cmd);
                               usage();
                       }
                       break;
               case 's' :
                       ksig = atoi(optarg);
                       if( ksig < 1 || ksig > SIGUSR2 ) {
                               fprintf(stderr, "%s: bad signal number: 
%s\n",
                                       cmd, optarg);
                               usage();
                       }
                       break;
               default:
                       usage();
               }
       }
                     
       if( xflag ) {
               fprintf(stderr, "+ ");
               for(i=optind; i<argc; i++) {
                       fprintf(stderr, "%s ", argv[i]);
               }
               fprintf(stderr, "\n");
       }
       childpid = fork();
       switch (childpid) {
       case -1  :
               fprintf(stderr, "%s: can not fork()\n", cmd);
               perror("");
               exit(252);
               break;
       case 0 :        /* child */
               break;
       default :       /* parent */
               signal(SIGALRM, timeout);
               signal(SIGHUP, timeout);
               signal(SIGINT, timeout);
               signal(SIGTERM, timeout);
               signal(SIGQUIT, timeout);
               signal(SIGPIPE, timeout);
               signal(SIGUSR1, timeout);
               signal(SIGUSR2, timeout);
               alarm(tlimit);
               do {
                       ws = wait(&status);
               } while ( (ws != childpid) && (ws < 0 && errno == EINTR) );
               alarm(0);
               if( timedout == SIGALRM ) {
                       if( xflag ) fprintf(stderr,
                               "%s: Command timed-out\n", cmd);
                       exit(254);
               }
               exit( (status & 255) ? status + 127 : status >> 8);
               break;
       }
/*
*      At this point, the child is executing this code.  Become
*      a process group leader to that our parent can kill all
*      of our processes not known by our parent.
*/
       setuid(myuid);  /* give up root access */
       setpgrp();
       execvp( argv[optind], &argv[optind] );
       fprintf( stderr, "%s: '%s' - not executed.  ", cmd, argv[optind] );
       perror( "" );
       exit( 253 );
}

usage()
{
       fprintf( stderr, "Usage:  %s [-t secs] [-s signal] [-x] command 
[ arg ..
. ]\n", cmd );
       exit(251);
}

/*
*      signal trap handler.  If signal receive is SIGALRM then
*      we send "ksig".  All other signals are sent as is to the
*      child process group leader.  This permits hangups,
*      interrupts, and quits, .... to be received by the new
*      process group.
*/
timeout(sig)
int     sig;
{
       timedout = sig == SIGALRM ? ksig : sig;
       if( childpid < 3 ) return;      /* fail safe protection */
       kill(-childpid, timedout);
       return;
}


- Paul

Micah Cowan wrote:
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> With Wget's default of 20 tries, and 900-second timeouts, the following
> bug report notes that Wget can sit on a download attempt for a total of
> 2.5 hours (actually, my math puts it at 5).
>
> https://savannah.gnu.org/bugs/index.php?27141
>
> Obviously, we can adjust these settings in wgetrc, but should that be
> necessary? Are people happy with the current timeout settings, and if
> not, what are some proposed better values?
>
> - --
> Micah J. Cowan
> Programmer, musician, typesetting enthusiast, gamer.
> Maintainer of GNU Wget and GNU Teseq
> http://micah.cowan.name/
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