var.c

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/*-
 * Copyright (c) 1991 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.
 */

#ifndef lint
static char sccsid[] = "@(#)var.c       5.3 (Berkeley) 4/12/91";
#endif /* not lint */

/*
 * Shell variables.
 */

#include "shell.h"
#include "output.h"
#include "expand.h"
#include "nodes.h"      /* for other headers */
#include "eval.h"       /* defines cmdenviron */
#include "exec.h"
#include "syntax.h"
#include "options.h"
#include "mail.h"
#include "var.h"
#include "memalloc.h"
#include "error.h"
#include "mystring.h"


#define VTABSIZE 39


struct varinit {
        struct var *var;
        int flags;
        char *text;
};


#if ATTY
struct var vatty;
#endif
struct var vifs;
struct var vmail;
struct var vmpath;
struct var vpath;
struct var vps1;
struct var vps2;
struct var vpse;
struct var vvers;
#if ATTY
struct var vterm;
#endif

const struct varinit varinit[] = {
#if ATTY
        {&vatty,        VSTRFIXED|VTEXTFIXED|VUNSET,    "ATTY="},
#endif
        {&vifs, VSTRFIXED|VTEXTFIXED,           "IFS= \t\n"},
        {&vmail,        VSTRFIXED|VTEXTFIXED|VUNSET,    "MAIL="},
        {&vmpath,       VSTRFIXED|VTEXTFIXED|VUNSET,    "MAILPATH="},
        {&vpath,        VSTRFIXED|VTEXTFIXED,           "PATH=:/bin:/usr/bin"},
        /* 
         * vps1 depends on uid
         */
        {&vps2, VSTRFIXED|VTEXTFIXED,           "PS2=> "},
        {&vpse, VSTRFIXED|VTEXTFIXED,           "PSE=* "},
#if ATTY
        {&vterm,        VSTRFIXED|VTEXTFIXED|VUNSET,    "TERM="},
#endif
        {NULL,  0,                              NULL}
};

struct var *vartab[VTABSIZE];

STATIC void unsetvar __P((char *));
STATIC struct var **hashvar __P((char *));
STATIC int varequal __P((char *, char *));

/*
 * Initialize the varable symbol tables and import the environment
 */

#ifdef mkinit
INCLUDE "var.h"
INIT {
        char **envp;
        extern char **environ;

        initvar();
        for (envp = environ ; *envp ; envp++) {
                if (strchr(*envp, '=')) {
                        setvareq(*envp, VEXPORT|VTEXTFIXED);
                }
        }
}
#endif


/*
 * This routine initializes the builtin variables.  It is called when the
 * shell is initialized and again when a shell procedure is spawned.
 */

void
initvar() {
        const struct varinit *ip;
        struct var *vp;
        struct var **vpp;

        for (ip = varinit ; (vp = ip->var) != NULL ; ip++) {
                if ((vp->flags & VEXPORT) == 0) {
                        vpp = hashvar(ip->text);
                        vp->next = *vpp;
                        *vpp = vp;
                        vp->text = ip->text;
                        vp->flags = ip->flags;
                }
        }
        /*
         * PS1 depends on uid
         */
        if ((vps1.flags & VEXPORT) == 0) {
                vpp = hashvar("PS1=");
                vps1.next = *vpp;
                *vpp = &vps1;
                vps1.text = getuid() ? "PS1=$ " : "PS1=# ";
                vps1.flags = VSTRFIXED|VTEXTFIXED;
        }
}

/*
 * Set the value of a variable.  The flags argument is ored with the
 * flags of the variable.  If val is NULL, the variable is unset.
 */

void
setvar(name, val, flags)
        char *name, *val;
        {
        char *p, *q;
        int len;
        int namelen;
        char *nameeq;
        int isbad;

        isbad = 0;
        p = name;
        if (! is_name(*p++))
                isbad = 1;
        for (;;) {
                if (! is_in_name(*p)) {
                        if (*p == '\0' || *p == '=')
                                break;
                        isbad = 1;
                }
                p++;
        }
        namelen = p - name;
        if (isbad)
                error("%.*s: is read only", namelen, name);
        len = namelen + 2;              /* 2 is space for '=' and '\0' */
        if (val == NULL) {
                flags |= VUNSET;
        } else {
                len += strlen(val);
        }
        p = nameeq = ckmalloc(len);
        q = name;
        while (--namelen >= 0)
                *p++ = *q++;
        *p++ = '=';
        *p = '\0';
        if (val)
                scopy(val, p);
        setvareq(nameeq, flags);
}



/*
 * Same as setvar except that the variable and value are passed in
 * the first argument as name=value.  Since the first argument will
 * be actually stored in the table, it should not be a string that
 * will go away.
 */

void
setvareq(s, flags)
        char *s;
        {
        struct var *vp, **vpp;

        vpp = hashvar(s);
        for (vp = *vpp ; vp ; vp = vp->next) {
                if (varequal(s, vp->text)) {
                        if (vp->flags & VREADONLY) {
                                int len = strchr(s, '=') - s;
                                error("%.*s: is read only", len, s);
                        }
                        INTOFF;
                        if (vp == &vpath)
                                changepath(s + 5);      /* 5 = strlen("PATH=") */
                        if ((vp->flags & (VTEXTFIXED|VSTACK)) == 0)
                                ckfree(vp->text);
                        vp->flags &=~ (VTEXTFIXED|VSTACK|VUNSET);
                        vp->flags |= flags;
                        vp->text = s;
                        if (vp == &vmpath || (vp == &vmail && ! mpathset()))
                                chkmail(1);
                        INTON;
                        return;
                }
        }
        /* not found */
        vp = ckmalloc(sizeof (*vp));
        vp->flags = flags;
        vp->text = s;
        vp->next = *vpp;
        *vpp = vp;
}



/*
 * Process a linked list of variable assignments.
 */

void
listsetvar(list)
        struct strlist *list;
        {
        struct strlist *lp;

        INTOFF;
        for (lp = list ; lp ; lp = lp->next) {
                setvareq(savestr(lp->text), 0);
        }
        INTON;
}



/*
 * Find the value of a variable.  Returns NULL if not set.
 */

char *
lookupvar(name)
        char *name;
        {
        struct var *v;

        for (v = *hashvar(name) ; v ; v = v->next) {
                if (varequal(v->text, name)) {
                        if (v->flags & VUNSET)
                                return NULL;
                        return strchr(v->text, '=') + 1;
                }
        }
        return NULL;
}



/*
 * Search the environment of a builtin command.  If the second argument
 * is nonzero, return the value of a variable even if it hasn't been
 * exported.
 */

char *
bltinlookup(name, doall)
        char *name;
        {
        struct strlist *sp;
        struct var *v;

        for (sp = cmdenviron ; sp ; sp = sp->next) {
                if (varequal(sp->text, name))
                        return strchr(sp->text, '=') + 1;
        }
        for (v = *hashvar(name) ; v ; v = v->next) {
                if (varequal(v->text, name)) {
                        if (v->flags & VUNSET
                         || ! doall && (v->flags & VEXPORT) == 0)
                                return NULL;
                        return strchr(v->text, '=') + 1;
                }
        }
        return NULL;
}



/*
 * Generate a list of exported variables.  This routine is used to construct
 * the third argument to execve when executing a program.
 */

char **
environment() {
        int nenv;
        struct var **vpp;
        struct var *vp;
        char **env, **ep;

        nenv = 0;
        for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
                for (vp = *vpp ; vp ; vp = vp->next)
                        if (vp->flags & VEXPORT)
                                nenv++;
        }
        ep = env = stalloc((nenv + 1) * sizeof *env);
        for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
                for (vp = *vpp ; vp ; vp = vp->next)
                        if (vp->flags & VEXPORT)
                                *ep++ = vp->text;
        }
        *ep = NULL;
        return env;
}


/*
 * Called when a shell procedure is invoked to clear out nonexported
 * variables.  It is also necessary to reallocate variables of with
 * VSTACK set since these are currently allocated on the stack.
 */

#ifdef mkinit
MKINIT void shprocvar();

SHELLPROC {
        shprocvar();
}
#endif

void
shprocvar() {
        struct var **vpp;
        struct var *vp, **prev;

        for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
                for (prev = vpp ; (vp = *prev) != NULL ; ) {
                        if ((vp->flags & VEXPORT) == 0) {
                                *prev = vp->next;
                                if ((vp->flags & VTEXTFIXED) == 0)
                                        ckfree(vp->text);
                                if ((vp->flags & VSTRFIXED) == 0)
                                        ckfree(vp);
                        } else {
                                if (vp->flags & VSTACK) {
                                        vp->text = savestr(vp->text);
                                        vp->flags &=~ VSTACK;
                                }
                                prev = &vp->next;
                        }
                }
        }
        initvar();
}



/*
 * Command to list all variables which are set.  Currently this command
 * is invoked from the set command when the set command is called without
 * any variables.
 */

int
showvarscmd(argc, argv)  char **argv; {
        struct var **vpp;
        struct var *vp;

        for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
                for (vp = *vpp ; vp ; vp = vp->next) {
                        if ((vp->flags & VUNSET) == 0)
                                out1fmt("%s\n", vp->text);
                }
        }
        return 0;
}



/*
 * The export and readonly commands.
 */

int
exportcmd(argc, argv)  char **argv; {
        struct var **vpp;
        struct var *vp;
        char *name;
        char *p;
        int flag = argv[0][0] == 'r'? VREADONLY : VEXPORT;

        listsetvar(cmdenviron);
        if (argc > 1) {
                while ((name = *argptr++) != NULL) {
                        if ((p = strchr(name, '=')) != NULL) {
                                p++;
                        } else {
                                vpp = hashvar(name);
                                for (vp = *vpp ; vp ; vp = vp->next) {
                                        if (varequal(vp->text, name)) {
                                                vp->flags |= flag;
                                                goto found;
                                        }
                                }
                        }
                        setvar(name, p, flag);
found:;
                }
        } else {
                for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
                        for (vp = *vpp ; vp ; vp = vp->next) {
                                if (vp->flags & flag) {
                                        for (p = vp->text ; *p != '=' ; p++)
                                                out1c(*p);
                                        out1c('\n');
                                }
                        }
                }
        }
        return 0;
}


/*
 * The "local" command.
 */

localcmd(argc, argv)  char **argv; {
        char *name;

        if (! in_function())
                error("Not in a function");
        while ((name = *argptr++) != NULL) {
                mklocal(name);
        }
        return 0;
}


/*
 * Make a variable a local variable.  When a variable is made local, it's
 * value and flags are saved in a localvar structure.  The saved values
 * will be restored when the shell function returns.  We handle the name
 * "-" as a special case.
 */

void
mklocal(name)
        char *name;
        {
        struct localvar *lvp;
        struct var **vpp;
        struct var *vp;

        INTOFF;
        lvp = ckmalloc(sizeof (struct localvar));
        if (name[0] == '-' && name[1] == '\0') {
                lvp->text = ckmalloc(sizeof optval);
                bcopy(optval, lvp->text, sizeof optval);
                vp = NULL;
        } else {
                vpp = hashvar(name);
                for (vp = *vpp ; vp && ! varequal(vp->text, name) ; vp = vp->next);
                if (vp == NULL) {
                        if (strchr(name, '='))
                                setvareq(savestr(name), VSTRFIXED);
                        else
                                setvar(name, NULL, VSTRFIXED);
                        vp = *vpp;      /* the new variable */
                        lvp->text = NULL;
                        lvp->flags = VUNSET;
                } else {
                        lvp->text = vp->text;
                        lvp->flags = vp->flags;
                        vp->flags |= VSTRFIXED|VTEXTFIXED;
                        if (strchr(name, '='))
                                setvareq(savestr(name), 0);
                }
        }
        lvp->vp = vp;
        lvp->next = localvars;
        localvars = lvp;
        INTON;
}


/*
 * Called after a function returns.
 */

void
poplocalvars() {
        struct localvar *lvp;
        struct var *vp;

        while ((lvp = localvars) != NULL) {
                localvars = lvp->next;
                vp = lvp->vp;
                if (vp == NULL) {       /* $- saved */
                        bcopy(lvp->text, optval, sizeof optval);
                        ckfree(lvp->text);
                } else if ((lvp->flags & (VUNSET|VSTRFIXED)) == VUNSET) {
                        unsetvar(vp->text);
                } else {
                        if ((vp->flags & VTEXTFIXED) == 0)
                                ckfree(vp->text);
                        vp->flags = lvp->flags;
                        vp->text = lvp->text;
                }
                ckfree(lvp);
        }
}


setvarcmd(argc, argv)  char **argv; {
        if (argc <= 2)
                return unsetcmd(argc, argv);
        else if (argc == 3)
                setvar(argv[1], argv[2], 0);
        else
                error("List assignment not implemented");
        return 0;
}


/*
 * The unset builtin command.  We unset the function before we unset the
 * variable to allow a function to be unset when there is a readonly variable
 * with the same name.
 */

unsetcmd(argc, argv)  char **argv; {
        char **ap;

        for (ap = argv + 1 ; *ap ; ap++) {
                unsetfunc(*ap);
                unsetvar(*ap);
        }
        return 0;
}


/*
 * Unset the specified variable.
 */

STATIC void
unsetvar(s)
        char *s;
        {
        struct var **vpp;
        struct var *vp;

        vpp = hashvar(s);
        for (vp = *vpp ; vp ; vpp = &vp->next, vp = *vpp) {
                if (varequal(vp->text, s)) {
                        INTOFF;
                        if (*(strchr(vp->text, '=') + 1) != '\0'
                         || vp->flags & VREADONLY) {
                                setvar(s, nullstr, 0);
                        }
                        vp->flags &=~ VEXPORT;
                        vp->flags |= VUNSET;
                        if ((vp->flags & VSTRFIXED) == 0) {
                                if ((vp->flags & VTEXTFIXED) == 0)
                                        ckfree(vp->text);
                                *vpp = vp->next;
                                ckfree(vp);
                        }
                        INTON;
                        return;
                }
        }
}



/*
 * Find the appropriate entry in the hash table from the name.
 */

STATIC struct var **
hashvar(p)
        register char *p;
        {
        unsigned int hashval;

        hashval = *p << 4;
        while (*p && *p != '=')
                hashval += *p++;
        return &vartab[hashval % VTABSIZE];
}



/*
 * Returns true if the two strings specify the same varable.  The first
 * variable name is terminated by '='; the second may be terminated by
 * either '=' or '\0'.
 */

STATIC int
varequal(p, q)
        register char *p, *q;
        {
        while (*p == *q++) {
                if (*p++ == '=')
                        return 1;
        }
        if (*p == '=' && *(q - 1) == '\0')
                return 1;
        return 0;
}

---