usr/src/lib/libc/stdlib/setenv.c

/*
 * Copyright (c) 1987, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * %sccs.include.redist.c%
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)setenv.c    8.1 (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */

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

char *__findenv __P((const char *, int *));

/*
 * setenv --
 *      Set the value of the environmental variable "name" to be
 *      "value".  If rewrite is set, replace any current value.
 */
setenv(name, value, rewrite)
        register const char *name;
        register const char *value;
        int rewrite;
{
        extern char **environ;
        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 = 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;
}