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+/****************************************************************/
+/* */
+/* putenv(3) */
+/* */
+/* Change or add an environment entry */
+/* */
+/****************************************************************/
+/* origination 1987-Oct-7 T. Holm */
+/****************************************************************/
+
+/*
+Path: hoptoad!pacbell!ames!ll-xn!mit-eddie!uw-beaver!ssc-vax!uvicctr!tholm
+From: tholm@uvicctr.UUCP (Terrence W. Holm)
+Newsgroups: comp.os.minix
+Subject: putenv(3)
+Message-ID: <395@uvicctr.UUCP>
+Date: 5 May 88 06:40:52 GMT
+Organization: University of Victoria, Victoria B.C. Canada
+
+EFTH Minix report #2 - May 1988 - putenv(3)
+
+This is an implementation of putenv(3) that we
+wrote for Minix. Please consider this a public
+domain program.
+*/
+
+#define NULL 0
+#define PSIZE sizeof(char *)
+
+extern char **environ;
+
+char *strchr();
+char *malloc();
+
+/****************************************************************/
+/* */
+/* int */
+/* putenv( entry ) */
+/* */
+/* The "entry" should follow the form */
+/* "NAME=VALUE". This routine will search the */
+/* user environment for "NAME" and replace its */
+/* value with "VALUE". */
+/* */
+/* Note that "entry" is not copied, it is used */
+/* as the environment entry. This means that it */
+/* must not be unallocated or otherwise modifed */
+/* by the caller, unless it is replaced by a */
+/* subsequent putenv(). */
+/* */
+/* If the name is not found in the environment, */
+/* then a new vector of pointers is allocated, */
+/* "entry" is put at the end and the global */
+/* variable "environ" is updated. */
+/* */
+/* This function normally returns 0, but -1 */
+/* is returned if it can not allocate enough */
+/* space using malloc(3), or "entry" does not */
+/* contain a '='. */
+/* */
+/****************************************************************/
+
+
+int
+putenv( entry )
+ char *entry;
+{
+ unsigned length;
+ unsigned size;
+ char *temp;
+ char **p;
+ char **new_environ;
+
+ /* Find the length of the "NAME=" */
+
+ temp = strchr(entry,'=');
+ if ( temp == 0 )
+ return( -1 );
+
+ length = (unsigned) (temp - entry + 1);
+
+
+ /* Scan through the environment looking for "NAME=" */
+
+ for ( p=environ; *p != 0 ; p++ )
+ if ( strncmp( entry, *p, length ) == 0 )
+ {
+ *p = entry;
+ return( 0 );
+ }
+
+
+ /* The name was not found, build a bigger environment */
+
+ size = p - environ;
+
+ new_environ = (char **) malloc( (size+2)*PSIZE );
+
+ if ( new_environ == (char **) NULL )
+ return( -1 );
+
+ memcpy ((char *) new_environ, (char *) environ, size*PSIZE );
+
+ new_environ[size] = entry;
+ new_environ[size+1] = NULL;
+
+ environ = new_environ;
+
+ return(0);
+}