usr/src/bin/sh/trap.c

/*-
 * 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.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char sccsid[] = "@(#)trap.c      8.1 (Berkeley) %G%";
#endif /* not lint */

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


/*
 * 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 */


extern char nullstr[1];         /* null string */

char *trap[MAXSIG+1];           /* trap handler commands */
MKINIT char sigmode[MAXSIG];    /* current value of signal */
char gotsig[MAXSIG];            /* indicates specified signal received */
int pendingsigs;                        /* indicates some signal received */

/*
 * The trap builtin.
 */

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

        if (argc <= 1) {
                for (signo = 0 ; signo <= MAXSIG ; signo++) {
                        if (trap[signo] != NULL)
                                out1fmt("%d: %s\n", signo, trap[signo]);
                }
                return 0;
        }
        ap = argv + 1;
        if (is_number(*ap))
                action = NULL;
        else
                action = *ap++;
        while (*ap) {
                if ((signo = number(*ap)) < 0 || signo > MAXSIG)
                        error("%s: bad trap", *ap);
                INTOFF;
                if (action)
                        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() {
        char **tp;

        for (tp = trap ; tp <= &trap[MAXSIG] ; 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.
 */

int
setsignal(signo) {
        int action;
        sig_t sigact;
        char *t;
        extern void onsig();
        extern sig_t getsigaction();

        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)
                                action = S_CATCH;
                        break;
                case SIGQUIT:
#ifdef DEBUG
                        {
                        extern int 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];
        if (*t == 0) {
                /*
                 * current setting unknown
                 */
                sigact = getsigaction(signo);
                if (sigact == SIG_IGN) {
                        if (mflag && (signo == SIGTSTP ||
                             signo == SIGTTIN || signo == SIGTTOU)) {
                                *t = S_IGN;     /* don't hard ignore these */
                        } else
                                *t = S_HARD_IGN;
                } else {
                        *t = S_RESET;   /* force to be set */
                }
        }
        if (*t == S_HARD_IGN || *t == action)
                return 0;
        switch (action) {
                case S_DFL:     sigact = SIG_DFL;       break;
                case S_CATCH:   sigact = onsig;         break;
                case S_IGN:     sigact = SIG_IGN;       break;
        }
        *t = action;
        return (int)signal(signo, sigact);
}

/*
 * Return the current setting for sig w/o changing it.
 */
sig_t
getsigaction(signo) {
        struct sigaction sa;

        if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
                error("Sigaction system call failed");

        return sa.sa_handler;
}

/*
 * Ignore a signal.
 */

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


#ifdef mkinit
INCLUDE "signames.h"
INCLUDE "trap.h"

SHELLPROC {
        char *sm;

        clear_traps();
        for (sm = sigmode ; sm < sigmode + MAXSIG ; sm++) {
                if (*sm == S_IGN)
                        *sm = S_HARD_IGN;
        }
}
#endif


/*
 * Signal handler.
 */

void
onsig(signo) {
        signal(signo, onsig);
        if (signo == SIGINT && trap[SIGINT] == NULL) {
                onint();
                return;
        }
        gotsig[signo - 1] = 1;
        pendingsigs++;
}


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

void
dotrap() {
        int i;
        int savestatus;

        for (;;) {
                for (i = 1 ; ; i++) {
                        if (gotsig[i - 1])
                                break;
                        if (i >= MAXSIG)
                                goto done;
                }
                gotsig[i - 1] = 0;
                savestatus=exitstatus;
                evalstring(trap[i]);
                exitstatus=savestatus;
        }
done:
        pendingsigs = 0;
}


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


void
setinteractive(on) {
        static int is_interactive;

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


/*
 * Called to exit the shell.
 */

void
exitshell(status) {
        struct jmploc loc1, loc2;
        char *p;

        TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
        if (setjmp(loc1.loc)) {
                goto l1;
        }
        if (setjmp(loc2.loc)) {
                goto l2;
        }
        handler = &loc1;
        if ((p = trap[0]) != NULL && *p != '\0') {
                trap[0] = NULL;
                evalstring(p);
        }
l1:   handler = &loc2;                  /* probably unnecessary */
        flushall();
#if JOBS
        setjobctl(0);
#endif
l2:   _exit(status);
}