src/commands/ash/exec.c

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/*-
 * 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.
 * 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.
 */

#ifndef lint
#if 0
static char sccsid[] = "@(#)exec.c      8.4 (Berkeley) 6/8/95";
#endif
#endif /* not lint */
/*
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/bin/sh/exec.c,v 1.24.2.1 2004/09/30 04:41:55 des Exp $");
*/

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>

/*
 * When commands are first encountered, they are entered in a hash table.
 * This ensures that a full path search will not have to be done for them
 * on each invocation.
 *
 * We should investigate converting to a linear search, even though that
 * would make the command name "hash" a misnomer.
 */

#include "shell.h"
#include "main.h"
#include "nodes.h"
#include "parser.h"
#include "redir.h"
#include "eval.h"
#include "exec.h"
#include "builtins.h"
#include "var.h"
#include "options.h"
#include "input.h"
#include "output.h"
#include "syntax.h"
#include "memalloc.h"
#include "error.h"
#include "init.h"
#include "mystring.h"
#include "show.h"
#include "jobs.h"
#include "alias.h"


#define CMDTABLESIZE 31         /* should be prime */
#define ARB 1                   /* actual size determined at run time */



struct tblentry {
        struct tblentry *next;  /* next entry in hash chain */
        union param param;      /* definition of builtin function */
        short cmdtype;          /* index identifying command */
        char rehash;            /* if set, cd done since entry created */
        char cmdname[ARB];      /* name of command */
};


STATIC struct tblentry *cmdtable[CMDTABLESIZE];
STATIC int builtinloc = -1;             /* index in path of %builtin, or -1 */
int exerrno = 0;                        /* Last exec error */


STATIC void tryexec(char *, char **, char **);
STATIC void printentry(struct tblentry *, int);
STATIC struct tblentry *cmdlookup(char *, int);
STATIC void delete_cmd_entry(void);
STATIC void addcmdentry(char *, struct cmdentry *);



/*
 * Exec a program.  Never returns.  If you change this routine, you may
 * have to change the find_command routine as well.
 */

void
shellexec(char **argv, char **envp, char *path, int index)
{
        char *cmdname;
        int e;

        if (strchr(argv[0], '/') != NULL) {
                tryexec(argv[0], argv, envp);
                e = errno;
        } else {
                e = ENOENT;
                while ((cmdname = padvance(&path, argv[0])) != NULL) {
                        if (--index < 0 && pathopt == NULL) {
                                tryexec(cmdname, argv, envp);
                                if (errno != ENOENT && errno != ENOTDIR)
                                        e = errno;
                        }
                        stunalloc(cmdname);
                }
        }

        /* Map to POSIX errors */
        switch (e) {
        case EACCES:
                exerrno = 126;
                break;
        case ENOENT:
                exerrno = 127;
                break;
        default:
                exerrno = 2;
                break;
        }
        if (e == ENOENT || e == ENOTDIR)
                exerror(EXEXEC, "%s: not found", argv[0]);
        exerror(EXEXEC, "%s: %s", argv[0], strerror(e));
}


STATIC void
tryexec(char *cmd, char **argv, char **envp)
{
        int e;

        execve(cmd, argv, envp);
#if !__minix_vmd
        e = errno;
        if (e == ENOEXEC) {
                initshellproc();
                setinputfile(cmd, 0);
                commandname = arg0 = savestr(argv[0]);
                setparam(argv + 1);
                exraise(EXSHELLPROC);
                /*NOTREACHED*/
        }
        errno = e;
#endif
}

/*
 * Do a path search.  The variable path (passed by reference) should be
 * set to the start of the path before the first call; padvance will update
 * this value as it proceeds.  Successive calls to padvance will return
 * the possible path expansions in sequence.  If an option (indicated by
 * a percent sign) appears in the path entry then the global variable
 * pathopt will be set to point to it; otherwise pathopt will be set to
 * NULL.
 */

char *pathopt;

char *
padvance(char **path, char *name)
{
        char *p, *q;
        char *start;
        int len;

        if (*path == NULL)
                return NULL;
        start = *path;
        for (p = start ; *p && *p != ':' && *p != '%' ; p++);
        len = p - start + strlen(name) + 2;     /* "2" is for '/' and '\0' */
        while (stackblocksize() < len)
                growstackblock();
        q = stackblock();
        if (p != start) {
                memcpy(q, start, p - start);
                q += p - start;
                *q++ = '/';
        }
        strcpy(q, name);
        pathopt = NULL;
        if (*p == '%') {
                pathopt = ++p;
                while (*p && *p != ':')  p++;
        }
        if (*p == ':')
                *path = p + 1;
        else
                *path = NULL;
        return stalloc(len);
}



/*** Command hashing code ***/


int
hashcmd(int argc __unused, char **argv __unused)
{
        struct tblentry **pp;
        struct tblentry *cmdp;
        int c;
        int verbose;
        struct cmdentry entry;
        char *name;

        verbose = 0;
        while ((c = nextopt("rv")) != '\0') {
                if (c == 'r') {
                        clearcmdentry(0);
                } else if (c == 'v') {
                        verbose++;
                }
        }
        if (*argptr == NULL) {
                for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
                        for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
                                if (cmdp->cmdtype == CMDNORMAL)
                                        printentry(cmdp, verbose);
                        }
                }
                return 0;
        }
        while ((name = *argptr) != NULL) {
                if ((cmdp = cmdlookup(name, 0)) != NULL
                 && (cmdp->cmdtype == CMDNORMAL
                     || (cmdp->cmdtype == CMDBUILTIN && builtinloc >= 0)))
                        delete_cmd_entry();
                find_command(name, &entry, 1, pathval());
                if (verbose) {
                        if (entry.cmdtype != CMDUNKNOWN) {      /* if no error msg */
                                cmdp = cmdlookup(name, 0);
                                if (cmdp != NULL)
                                        printentry(cmdp, verbose);
                                else
                                        outfmt(&errout, "%s: not found\n", name);
                        }
                        flushall();
                }
                argptr++;
        }
        return 0;
}


STATIC void
printentry(struct tblentry *cmdp, int verbose)
{
        int index;
        char *path;
        char *name;

        if (cmdp->cmdtype == CMDNORMAL) {
                index = cmdp->param.index;
                path = pathval();
                do {
                        name = padvance(&path, cmdp->cmdname);
                        stunalloc(name);
                } while (--index >= 0);
                out1str(name);
        } else if (cmdp->cmdtype == CMDBUILTIN) {
                out1fmt("builtin %s", cmdp->cmdname);
        } else if (cmdp->cmdtype == CMDFUNCTION) {
                out1fmt("function %s", cmdp->cmdname);
                if (verbose) {
                        INTOFF;
                        name = commandtext(cmdp->param.func);
                        out1c(' ');
                        out1str(name);
                        ckfree(name);
                        INTON;
                }
#if DEBUG
        } else {
                error("internal error: cmdtype %d", cmdp->cmdtype);
#endif
        }
        if (cmdp->rehash)
                out1c('*');
        out1c('\n');
}



/*
 * Resolve a command name.  If you change this routine, you may have to
 * change the shellexec routine as well.
 */

void
find_command(char *name, struct cmdentry *entry, int printerr, char *path)
{
        struct tblentry *cmdp;
        int index;
        int prev;
        char *fullname;
        struct stat statb;
        int e;
        int i;

        /* If name contains a slash, don't use the hash table */
        if (strchr(name, '/') != NULL) {
                entry->cmdtype = CMDNORMAL;
                entry->u.index = 0;
                return;
        }

        /* If name is in the table, and not invalidated by cd, we're done */
        if ((cmdp = cmdlookup(name, 0)) != NULL && cmdp->rehash == 0)
                goto success;

        /* If %builtin not in path, check for builtin next */
        if (builtinloc < 0 && (i = find_builtin(name)) >= 0) {
                INTOFF;
                cmdp = cmdlookup(name, 1);
                cmdp->cmdtype = CMDBUILTIN;
                cmdp->param.index = i;
                INTON;
                goto success;
        }

        /* We have to search path. */
        prev = -1;              /* where to start */
        if (cmdp) {             /* doing a rehash */
                if (cmdp->cmdtype == CMDBUILTIN)
                        prev = builtinloc;
                else
                        prev = cmdp->param.index;
        }

        e = ENOENT;
        index = -1;
loop:
        while ((fullname = padvance(&path, name)) != NULL) {
                stunalloc(fullname);
                index++;
                if (pathopt) {
                        if (prefix("builtin", pathopt)) {
                                if ((i = find_builtin(name)) < 0)
                                        goto loop;
                                INTOFF;
                                cmdp = cmdlookup(name, 1);
                                cmdp->cmdtype = CMDBUILTIN;
                                cmdp->param.index = i;
                                INTON;
                                goto success;
                        } else if (prefix("func", pathopt)) {
                                /* handled below */
                        } else {
                                goto loop;      /* ignore unimplemented options */
                        }
                }
                /* if rehash, don't redo absolute path names */
                if (fullname[0] == '/' && index <= prev) {
                        if (index < prev)
                                goto loop;
                        TRACE(("searchexec \"%s\": no change\n", name));
                        goto success;
                }
                if (stat(fullname, &statb) < 0) {
                        if (errno != ENOENT && errno != ENOTDIR)
                                e = errno;
                        goto loop;
                }
                e = EACCES;     /* if we fail, this will be the error */
                if (!S_ISREG(statb.st_mode))
                        goto loop;
                if (pathopt) {          /* this is a %func directory */
                        stalloc(strlen(fullname) + 1);
                        readcmdfile(fullname);
                        if ((cmdp = cmdlookup(name, 0)) == NULL || cmdp->cmdtype != CMDFUNCTION)
                                error("%s not defined in %s", name, fullname);
                        stunalloc(fullname);
                        goto success;
                }
#ifdef notdef
                if (statb.st_uid == geteuid()) {
                        if ((statb.st_mode & 0100) == 0)
                                goto loop;
                } else if (statb.st_gid == getegid()) {
                        if ((statb.st_mode & 010) == 0)
                                goto loop;
                } else {
                        if ((statb.st_mode & 01) == 0)
                                goto loop;
                }
#endif
                TRACE(("searchexec \"%s\" returns \"%s\"\n", name, fullname));
                INTOFF;
                cmdp = cmdlookup(name, 1);
                cmdp->cmdtype = CMDNORMAL;
                cmdp->param.index = index;
                INTON;
                goto success;
        }

        /* We failed.  If there was an entry for this command, delete it */
        if (cmdp)
                delete_cmd_entry();
        if (printerr) {
                if (e == ENOENT || e == ENOTDIR)
                        outfmt(out2, "%s: not found\n", name);
                else
                        outfmt(out2, "%s: %s\n", name, strerror(e));
        }
        entry->cmdtype = CMDUNKNOWN;
        return;

success:
        cmdp->rehash = 0;
        entry->cmdtype = cmdp->cmdtype;
        entry->u = cmdp->param;
}



/*
 * Search the table of builtin commands.
 */

int
find_builtin(char *name)
{
        const struct builtincmd *bp;

        for (bp = builtincmd ; bp->name ; bp++) {
                if (*bp->name == *name && equal(bp->name, name))
                        return bp->code;
        }
        return -1;
}



/*
 * Called when a cd is done.  Marks all commands so the next time they
 * are executed they will be rehashed.
 */

void
hashcd(void)
{
        struct tblentry **pp;
        struct tblentry *cmdp;

        for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
                for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
                        if (cmdp->cmdtype == CMDNORMAL
                         || (cmdp->cmdtype == CMDBUILTIN && builtinloc >= 0))
                                cmdp->rehash = 1;
                }
        }
}



/*
 * Called before PATH is changed.  The argument is the new value of PATH;
 * pathval() still returns the old value at this point.  Called with
 * interrupts off.
 */

void
changepath(const char *newval)
{
        const char *old, *new;
        int index;
        int firstchange;
        int bltin;

        old = pathval();
        new = newval;
        firstchange = 9999;     /* assume no change */
        index = 0;
        bltin = -1;
        for (;;) {
                if (*old != *new) {
                        firstchange = index;
                        if ((*old == '\0' && *new == ':')
                         || (*old == ':' && *new == '\0'))
                                firstchange++;
                        old = new;      /* ignore subsequent differences */
                }
                if (*new == '\0')
                        break;
                if (*new == '%' && bltin < 0 && prefix("builtin", new + 1))
                        bltin = index;
                if (*new == ':') {
                        index++;
                }
                new++, old++;
        }
        if (builtinloc < 0 && bltin >= 0)
                builtinloc = bltin;             /* zap builtins */
        if (builtinloc >= 0 && bltin < 0)
                firstchange = 0;
        clearcmdentry(firstchange);
        builtinloc = bltin;
}


/*
 * Clear out command entries.  The argument specifies the first entry in
 * PATH which has changed.
 */

void
clearcmdentry(int firstchange)
{
        struct tblentry **tblp;
        struct tblentry **pp;
        struct tblentry *cmdp;

        INTOFF;
        for (tblp = cmdtable ; tblp < &cmdtable[CMDTABLESIZE] ; tblp++) {
                pp = tblp;
                while ((cmdp = *pp) != NULL) {
                        if ((cmdp->cmdtype == CMDNORMAL &&
                             cmdp->param.index >= firstchange)
                         || (cmdp->cmdtype == CMDBUILTIN &&
                             builtinloc >= firstchange)) {
                                *pp = cmdp->next;
                                ckfree(cmdp);
                        } else {
                                pp = &cmdp->next;
                        }
                }
        }
        INTON;
}


/*
 * Delete all functions.
 */

#ifdef mkinit
INCLUDE "exec.h"
SHELLPROC {
        deletefuncs();
}
#endif

void
deletefuncs(void)
{
        struct tblentry **tblp;
        struct tblentry **pp;
        struct tblentry *cmdp;

        INTOFF;
        for (tblp = cmdtable ; tblp < &cmdtable[CMDTABLESIZE] ; tblp++) {
                pp = tblp;
                while ((cmdp = *pp) != NULL) {
                        if (cmdp->cmdtype == CMDFUNCTION) {
                                *pp = cmdp->next;
                                freefunc(cmdp->param.func);
                                ckfree(cmdp);
                        } else {
                                pp = &cmdp->next;
                        }
                }
        }
        INTON;
}



/*
 * Locate a command in the command hash table.  If "add" is nonzero,
 * add the command to the table if it is not already present.  The
 * variable "lastcmdentry" is set to point to the address of the link
 * pointing to the entry, so that delete_cmd_entry can delete the
 * entry.
 */

STATIC struct tblentry **lastcmdentry;


STATIC struct tblentry *
cmdlookup(char *name, int add)
{
        int hashval;
        char *p;
        struct tblentry *cmdp;
        struct tblentry **pp;

        p = name;
        hashval = *p << 4;
        while (*p)
                hashval += *p++;
        hashval &= 0x7FFF;
        pp = &cmdtable[hashval % CMDTABLESIZE];
        for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
                if (equal(cmdp->cmdname, name))
                        break;
                pp = &cmdp->next;
        }
        if (add && cmdp == NULL) {
                INTOFF;
                cmdp = *pp = ckmalloc(sizeof (struct tblentry) - ARB
                                        + strlen(name) + 1);
                cmdp->next = NULL;
                cmdp->cmdtype = CMDUNKNOWN;
                cmdp->rehash = 0;
                strcpy(cmdp->cmdname, name);
                INTON;
        }
        lastcmdentry = pp;
        return cmdp;
}

/*
 * Delete the command entry returned on the last lookup.
 */

STATIC void
delete_cmd_entry(void)
{
        struct tblentry *cmdp;

        INTOFF;
        cmdp = *lastcmdentry;
        *lastcmdentry = cmdp->next;
        ckfree(cmdp);
        INTON;
}



/*
 * Add a new command entry, replacing any existing command entry for
 * the same name.
 */

static void
addcmdentry(char *name, struct cmdentry *entry)
{
        struct tblentry *cmdp;

        INTOFF;
        cmdp = cmdlookup(name, 1);
        if (cmdp->cmdtype == CMDFUNCTION) {
                freefunc(cmdp->param.func);
        }
        cmdp->cmdtype = entry->cmdtype;
        cmdp->param = entry->u;
        INTON;
}


/*
 * Define a shell function.
 */

void
defun(char *name, union node *func)
{
        struct cmdentry entry;

        INTOFF;
        entry.cmdtype = CMDFUNCTION;
        entry.u.func = copyfunc(func);
        addcmdentry(name, &entry);
        INTON;
}


/*
 * Delete a function if it exists.
 */

int
unsetfunc(char *name)
{
        struct tblentry *cmdp;

        if ((cmdp = cmdlookup(name, 0)) != NULL && cmdp->cmdtype == CMDFUNCTION) {
                freefunc(cmdp->param.func);
                delete_cmd_entry();
                return (0);
        }
        return (0);
}

/*
 * Locate and print what a word is...
 */

int
typecmd(int argc, char **argv)
{
        struct cmdentry entry;
        struct tblentry *cmdp;
        char **pp;
        struct alias *ap;
        int i;
        int error = 0;
        extern char *const parsekwd[];

        for (i = 1; i < argc; i++) {
                out1str(argv[i]);
                /* First look at the keywords */
                for (pp = (char **)parsekwd; *pp; pp++)
                        if (**pp == *argv[i] && equal(*pp, argv[i]))
                                break;

                if (*pp) {
                        out1str(" is a shell keyword\n");
                        continue;
                }

                /* Then look at the aliases */
                if ((ap = lookupalias(argv[i], 1)) != NULL) {
                        out1fmt(" is an alias for %s\n", ap->val);
                        continue;
                }

                /* Then check if it is a tracked alias */
                if ((cmdp = cmdlookup(argv[i], 0)) != NULL) {
                        entry.cmdtype = cmdp->cmdtype;
                        entry.u = cmdp->param;
                }
                else {
                        /* Finally use brute force */
                        find_command(argv[i], &entry, 0, pathval());
                }

                switch (entry.cmdtype) {
                case CMDNORMAL: {
                        if (strchr(argv[i], '/') == NULL) {
                                char *path = pathval(), *name;
                                int j = entry.u.index;
                                do {
                                        name = padvance(&path, argv[i]);
                                        stunalloc(name);
                                } while (--j >= 0);
                                out1fmt(" is%s %s\n",
                                    cmdp ? " a tracked alias for" : "", name);
                        } else {
                                if (access(argv[i], X_OK) == 0)
                                        out1fmt(" is %s\n", argv[i]);
                                else
                                        out1fmt(": %s\n", strerror(errno));
                        }
                        break;
                }
                case CMDFUNCTION:
                        out1str(" is a shell function\n");
                        break;

                case CMDBUILTIN:
                        out1str(" is a shell builtin\n");
                        break;

                default:
                        out1str(": not found\n");
                        error |= 127;
                        break;
                }
        }
        return error;
}

/*
 * $PchId: exec.c,v 1.6 2006/04/10 14:47:03 philip Exp $
 */

---