summaryrefslogtreecommitdiffstats
path: root/putenv.c
blob: 2a907f902553a2da9c597da3edba8e1d57a031f1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
/* Copyright (c) 2008, 2009
 *      Juergen Weigert (jnweiger@immd4.informatik.uni-erlangen.de)
 *      Michael Schroeder (mlschroe@immd4.informatik.uni-erlangen.de)
 *      Micah Cowan (micah@cowan.name)
 *      Sadrul Habib Chowdhury (sadrul@users.sourceforge.net)
 * Copyright (c) 1993-2002, 2003, 2005, 2006, 2007
 *      Juergen Weigert (jnweiger@immd4.informatik.uni-erlangen.de)
 *      Michael Schroeder (mlschroe@immd4.informatik.uni-erlangen.de)
 * Copyright (c) 1987 Oliver Laumann
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program (see the file COPYING); if not, see
 * http://www.gnu.org/licenses/, or contact Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA  02111-1301  USA
 *
 ****************************************************************
 */

/*
 *  putenv  --  put value into environment
 *
 *  Usage:  i = putenv (string)
 *    int i;
 *    char  *string;
 *
 *  where string is of the form <name>=<value>.
 *  If "value" is 0, then "name" will be deleted from the environment.
 *  Putenv returns 0 normally, -1 on error (not enough core for malloc).
 *
 *  Putenv may need to add a new name into the environment, or to
 *  associate a value longer than the current value with a particular
 *  name.  So, to make life simpler, putenv() copies your entire
 *  environment into the heap (i.e. malloc()) from the stack
 *  (i.e. where it resides when your process is initiated) the first
 *  time you call it.
 *
 *  HISTORY
 *  3-Sep-91 Michael Schroeder (mlschroe). Modified to behave as
 *    as putenv.
 * 16-Aug-91 Tim MacKenzie (tym) at Monash University. Modified for
 *    use in screen (iScreen) (ignores final int parameter)
 * 14-Oct-85 Michael Mauldin (mlm) at Carnegie-Mellon University
 *      Ripped out of CMU lib for Rob-O-Matic portability
 * 20-Nov-79  Steven Shafer (sas) at Carnegie-Mellon University
 *    Created for VAX.  Too bad Bell Labs didn't provide this.  It's
 *    unfortunate that you have to copy the whole environment onto the
 *    heap, but the bookkeeping-and-not-so-much-copying approach turns
 *    out to be much hairier.  So, I decided to do the simple thing,
 *    copying the entire environment onto the heap the first time you
 *    call putenv(), then doing realloc() uniformly later on.
 */

#include "config.h"

#ifdef NEEDPUTENV

#if defined(__STDC__)
# define __P(a) a
#else
# define __P(a) ()
#endif

char  *malloc __P((int));
char  *realloc __P((char *, int));
void   free __P((char *));
int    sprintf __P((char *, char *, ...));

#define EXTRASIZE 5		/* increment to add to env. size */

static int  envsize = -1;	/* current size of environment */
extern char **environ;		/* the global which is your env. */

static int  findenv __P((char *));  /* look for a name in the env. */
static int  newenv __P((void));     /* copy env. from stack to heap */
static int  moreenv __P((void));    /* incr. size of env. */

int
unsetenv(name)
char *name;
{
  register int i;
  
  if (envsize < 0)
    {				/* first time putenv called */
      if (newenv() < 0)		/* copy env. to heap */
	return -1;
    }
  i = findenv(name);
  if (i < 0)
    return 0;			/* Already here */
  
  free(environ[i]);
  if (envsize > 0)
    envsize--;
  for (; environ[i]; i++)
    environ[i] = environ[i+1];
  return 0;			/* Already here */
}

int
putenv(string)
char *string;
{ 
  register int  i;
  register char *p;
  
  if (envsize < 0)
    {				/* first time putenv called */
      if (newenv() < 0)		/* copy env. to heap */
	return -1;
    }
  
  i = findenv(string);		/* look for name in environment */

  if (i < 0)
    {			/* name must be added */
      for (i = 0; environ[i]; i++);
      if (i >= (envsize - 1))
	{			/* need new slot */
	  if (moreenv() < 0)
	    return -1;
	}
      p = malloc(strlen(string) + 1);
      if (p == 0)		/* not enough core */
	return -1;
      environ[i + 1] = 0;	/* new end of env. */
    }
  else
    {			/* name already in env. */
      p = realloc(environ[i], strlen(string) + 1);
      if (p == 0)
	return -1;
    }
  sprintf(p, "%s", string); /* copy into env. */
  environ[i] = p;
  
  return 0;
}

static int
findenv(name)
char *name;
{
  register char *namechar, *envchar;
  register int  i, found;
  
  found = 0;
  for (i = 0; environ[i] && !found; i++)
    { 
      envchar = environ[i];
      namechar = name;
      while (*namechar && *namechar != '=' && (*namechar == *envchar))
        { 
	  namechar++;
	  envchar++;
        }
      found = ((*namechar == '\0' || *namechar == '=') && *envchar == '=');
    }
  return found ? i - 1 : -1;
}

static int
newenv()
{ 
  register char **env, *elem;
  register int i, esize;

  for (i = 0; environ[i]; i++)
    ;
  esize = i + EXTRASIZE + 1;
  env = (char **)malloc(esize * sizeof (elem));
  if (env == 0)
    return -1;

  for (i = 0; environ[i]; i++)
    { 
      elem = malloc(strlen(environ[i]) + 1);
      if (elem == 0)
	return -1;
      env[i] = elem;
      strcpy(elem, environ[i]);
    }
   
  env[i] = 0;
  environ = env;
  envsize = esize;
  return 0;
}

static int
moreenv()
{ 
  register int  esize;
  register char **env;
  
  esize = envsize + EXTRASIZE;
  env = (char **)realloc((char *)environ, esize * sizeof (*env));
  if (env == 0)
    return -1;
  environ = env;
  envsize = esize;
  return 0;
}

#endif /* NEEDPUTENV */