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