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getenv.c revision 1.2 
      1 /*
      2  * Copyright (c) 1987 Regents of the University of California.
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  * 3. All advertising materials mentioning features or use of this software
     14  *    must display the following acknowledgement:
     15  *	This product includes software developed by the University of
     16  *	California, Berkeley and its contributors.
     17  * 4. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  */
     33 
     34 #if defined(LIBC_SCCS) && !defined(lint)
     35 /*static char sccsid[] = "from: @(#)getenv.c	5.8 (Berkeley) 2/23/91";*/
     36 static char rcsid[] = "$Id: getenv.c,v 1.2 1993/08/01 18:37:09 mycroft Exp $";
     37 #endif /* LIBC_SCCS and not lint */
     38 
     39 #include <stdlib.h>
     40 #include <stddef.h>
     41 #include <string.h>
     42 
     43 /*
     44  * getenv --
     45  *	Returns ptr to value associated with name, if any, else NULL.
     46  */
     47 char *
     48 getenv(name)
     49 	const char *name;
     50 {
     51 	int offset;
     52 	char *_findenv();
     53 
     54 	return(_findenv(name, &offset));
     55 }
     56 
     57 /*
     58  * _findenv --
     59  *	Returns pointer to value associated with name, if any, else NULL.
     60  *	Sets offset to be the offset of the name/value combination in the
     61  *	environmental array, for use by setenv(3) and unsetenv(3).
     62  *	Explicitly removes '=' in argument name.
     63  *
     64  *	This routine *should* be a static; don't use it.
     65  */
     66 char *
     67 _findenv(name, offset)
     68 	register char *name;
     69 	int *offset;
     70 {
     71 	extern char **environ;
     72 	register int len;
     73 	register char **P, *C;
     74 
     75 	for (C = name, len = 0; *C && *C != '='; ++C, ++len);
     76 	for (P = environ; *P; ++P)
     77 		if (!strncmp(*P, name, len))
     78 			if (*(C = *P + len) == '=') {
     79 				*offset = P - environ;
     80 				return(++C);
     81 			}
     82 	return(NULL);
     83 }
     84