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trap.c

/*    $NetBSD: trap.c,v 1.28 2002/11/24 22:35:43 christos Exp $   */

/*-
 * Copyright (c) 1991, 1993
 *    The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the University of
 *    California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)trap.c  8.5 (Berkeley) 6/5/95";
#else
__RCSID("$NetBSD: trap.c,v 1.28 2002/11/24 22:35:43 christos Exp $");
#endif
#endif /* not lint */

#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

#include "shell.h"
#include "main.h"
#include "nodes.h"      /* for other headers */
#include "eval.h"
#include "jobs.h"
#include "show.h"
#include "options.h"
#include "syntax.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include "trap.h"
#include "mystring.h"

#ifdef HETIO
#include "hetio.h"
#endif

/*
 * Sigmode records the current value of the signal handlers for the various
 * modes.  A value of zero means that the current handler is not known.
 * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
 */

#define S_DFL 1               /* default signal handling (SIG_DFL) */
#define S_CATCH 2       /* signal is caught */
#define S_IGN 3               /* signal is ignored (SIG_IGN) */
#define S_HARD_IGN 4          /* signal is ignored permenantly */
#define S_RESET 5       /* temporary - to reset a hard ignored sig */


/* trap handler commands */
char *trap[NSIG];
/* current value of signal */
static char sigmode[NSIG - 1];
/* indicates specified signal received */
char gotsig[NSIG - 1];
/* last pending signal */
volatile sig_atomic_t pendingsigs;
/* do we generate EXSIG events */
int exsig;

extern char *signal_names[];

#ifdef mkinit
INCLUDE <signal.h>
INIT {
      signal(SIGCHLD, SIG_DFL);
}
#endif

/*
 * The trap builtin.
 */

int
trapcmd(int argc, char **argv)
{
      char *action;
      char **ap;
      int signo;

      nextopt(nullstr);
      ap = argptr;
      if (!*ap) {
            for (signo = 0 ; signo < NSIG ; signo++) {
                  if (trap[signo] != NULL) {
                        out1fmt(
                              "trap -- %s %s\n",
                              single_quote(trap[signo]),
                              signal_names[signo]
                        );
                  }
            }
            return 0;
      }
      if (!ap[1])
            action = NULL;
      else
            action = *ap++;
      while (*ap) {
            if ((signo = decode_signal(*ap, 0)) < 0)
                  error("%s: bad trap", *ap);
            INTOFF;
            if (action) {
                  if (action[0] == '-' && action[1] == '\0')
                        action = NULL;
                  else
                        action = savestr(action);
            }
            if (trap[signo])
                  ckfree(trap[signo]);
            trap[signo] = action;
            if (signo != 0)
                  setsignal(signo);
            INTON;
            ap++;
      }
      return 0;
}



/*
 * Clear traps on a fork.
 */

void
clear_traps(void)
{
      char **tp;

      for (tp = trap ; tp < &trap[NSIG] ; tp++) {
            if (*tp && **tp) {      /* trap not NULL or SIG_IGN */
                  INTOFF;
                  ckfree(*tp);
                  *tp = NULL;
                  if (tp != &trap[0])
                        setsignal(tp - trap);
                  INTON;
            }
      }
}



/*
 * Set the signal handler for the specified signal.  The routine figures
 * out what it should be set to.
 */

void
setsignal(int signo)
{
      int action;
      char *t, tsig;
      struct sigaction act;

      if ((t = trap[signo]) == NULL)
            action = S_DFL;
      else if (*t != '\0')
            action = S_CATCH;
      else
            action = S_IGN;
      if (rootshell && action == S_DFL) {
            switch (signo) {
            case SIGINT:
                  if (iflag || minusc || sflag == 0)
                        action = S_CATCH;
                  break;
            case SIGQUIT:
#ifdef DEBUG
                  if (debug)
                        break;
#endif
                  /* FALLTHROUGH */
            case SIGTERM:
                  if (iflag)
                        action = S_IGN;
                  break;
#if JOBS
            case SIGTSTP:
            case SIGTTOU:
                  if (mflag)
                        action = S_IGN;
                  break;
#endif
            }
      }

      t = &sigmode[signo - 1];
      tsig = *t;
      if (tsig == 0) {
            /*
             * current setting unknown
             */
            if (sigaction(signo, 0, &act) == -1) {
                  /*
                   * Pretend it worked; maybe we should give a warning
                   * here, but other shells don't. We don't alter
                   * sigmode, so that we retry every time.
                   */
                  return;
            }
            if (act.sa_handler == SIG_IGN) {
                  if (mflag && (signo == SIGTSTP ||
                       signo == SIGTTIN || signo == SIGTTOU)) {
                        tsig = S_IGN;     /* don't hard ignore these */
                  } else
                        tsig = S_HARD_IGN;
            } else {
                  tsig = S_RESET;   /* force to be set */
            }
      }
      if (tsig == S_HARD_IGN || tsig == action)
            return;
      switch (action) {
      case S_CATCH:
            act.sa_handler = onsig;
            break;
      case S_IGN:
            act.sa_handler = SIG_IGN;
            break;
      default:
            act.sa_handler = SIG_DFL;
      }
      *t = action;
      act.sa_flags = 0;
      sigfillset(&act.sa_mask);
      sigaction(signo, &act, 0);
}

/*
 * Ignore a signal.
 */

void
ignoresig(int signo)
{
      if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
            signal(signo, SIG_IGN);
      }
      sigmode[signo - 1] = S_HARD_IGN;
}



/*
 * Signal handler.
 */

void
onsig(int signo)
{
      gotsig[signo - 1] = 1;
      pendingsigs = signo;

      if (exsig || (signo == SIGINT && !trap[SIGINT])) {
            if (!suppressint)
                  onint();
            intpending = 1;
      }
}



/*
 * Called to execute a trap.  Perhaps we should avoid entering new trap
 * handlers while we are executing a trap handler.
 */

void
dotrap(void)
{
      char *p;
      char *q;
      int savestatus;

      savestatus = exitstatus;
      q = gotsig;
      while (pendingsigs = 0, barrier(), (p = memchr(q, 1, NSIG - 1))) {
            *p = 0;
            p = trap[p - q + 1];
            if (!p)
                  continue;
            evalstring(p);
            exitstatus = savestatus;
      }
}



/*
 * Controls whether the shell is interactive or not.
 */


void
setinteractive(int on)
{
      static int is_interactive;

      if (++on == is_interactive)
            return;
      is_interactive = on;
      setsignal(SIGINT);
      setsignal(SIGQUIT);
      setsignal(SIGTERM);
}



/*
 * Called to exit the shell.
 */

void
exitshell(void)
{
      struct jmploc loc;
      char *p;
      int status;
      int jmp;

#ifdef HETIO
      hetio_reset_term();
#endif
      jmp = setjmp(loc.loc);
      status = exitstatus;
      TRACE(("pid %d, exitshell(%d)\n", getpid(), status));
      if (jmp)
            goto out;
      handler = &loc;
      if ((p = trap[0]) != NULL && *p != '\0') {
            trap[0] = NULL;
            evalstring(p);
      }
      flushall();
out:
      _exit(status);
      /* NOTREACHED */
}

int decode_signal(const char *string, int minsig)
{
      int signo;

      if (is_number(string)) {
            signo = atoi(string);
            if (signo >= NSIG) {
                  return -1;
            }
            return signo;
      }

      for (signo = minsig; signo < NSIG; signo++) {
            if (!strcasecmp(string, signal_names[signo])) {
                  return signo;
            }
      }

      return -1;
}

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