Serving the Web/ServingTheWeb1995.disc1of1.iso/linux/slacksrce/d/libc/libc-4.6/libc-4/libc-linux/bsd/setenv.c

C/C++ Source or Header | 1994-08-23 | 4.5 KB | 148 lines

/*
 * Copyright (c) 1987 Regents of the University of California.
 * All rights reserved.
 *
 * 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)setenv.c    5.6 (Berkeley) 6/4/91";
#endif /* LIBC_SCCS and not lint */

#include <stddef.h>
#include <stdlib.h>
#include <string.h>

#define environ    __environ

/*
 * _findenv --
 *    Returns pointer to value associated with name, if any, else NULL.
 *    Sets offset to be the offset of the name/value combination in the
 *    environmental array, for use by setenv(3) and unsetenv(3).
 *    Explicitly removes '=' in argument name.
 *
 *    This routine *should* be a static; don't use it.
 */
static char *
_findenv(name, offset)
    register const char *name;
    int *offset;
{
    register int len;
    register char **P;
    register const char *C;

    for (C = name, len = 0; *C && *C != '='; ++C, ++len);
    for (P = environ; *P; ++P)
        if (!strncmp(*P, name, len))
            if (*(C = *P + len) == '=') {
                *offset = P - environ;
                return((char*)++C);
            }
    return(NULL);
}

/*
 * setenv --
 *    Set the value of the environmental variable "name" to be
 *    "value".  If rewrite is set, replace any current value.
 */
int
setenv(name, value, rewrite)
    register const char *name;
    register const char *value;
    int rewrite;
{
    static int alloced;            /* if allocated space before */
    register char *C;
    int l_value, offset;

    if (*value == '=')            /* no `=' in value */
        ++value;
    l_value = strlen(value);
    if ((C = _findenv(name, &offset))) {    /* find if already exists */
        if (!rewrite)
            return (0);
        if (strlen(C) >= l_value) {    /* old larger; copy over */
            while ((*C++ = *value++));
            return (0);
        }
    } else {                    /* create new slot */
        register int    cnt;
        register char    **P;

        for (P = environ, cnt = 0; *P; ++P, ++cnt);
        if (alloced) {            /* just increase size */
            environ = (char **)realloc((char *)environ,
                (size_t)(sizeof(char *) * (cnt + 2)));
            if (!environ)
                return (-1);
        }
        else {                /* get new space */
            alloced = 1;        /* copy old entries into it */
            P = (char **)malloc((size_t)(sizeof(char *) *
                (cnt + 2)));
            if (!P)
                return (-1);
            bcopy(environ, P, cnt * sizeof(char *));
            environ = P;
        }
        environ[cnt + 1] = NULL;
        offset = cnt;
    }
    for (C = (char *)name; *C && *C != '='; ++C);    /* no `=' in name */
    if (!(environ[offset] =            /* name + `=' + value */
        malloc((size_t)((int)(C - name) + l_value + 2))))
        return (-1);
    for (C = environ[offset]; (*C = *name++) && *C != '='; ++C)
        ;
    for (*C++ = '='; (*C++ = *value++); )
        ;
    return (0);
}

/*
 * unsetenv(name) --
 *    Delete environmental variable "name".
 */
void
unsetenv(name)
    const char    *name;
{
    extern char **environ;
    register char **P;
    int offset;

    while (_findenv(name, &offset))        /* if set multiple times */
        for (P = &environ[offset];; ++P)
            if (!(*P = *(P + 1)))
                break;
}