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1 : /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 : /* This Source Code Form is subject to the terms of the Mozilla Public
3 : * License, v. 2.0. If a copy of the MPL was not distributed with this
4 : * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
5 :
6 : #ifndef prenv_h___
7 : #define prenv_h___
8 :
9 : #include "prtypes.h"
10 :
11 : /*******************************************************************************/
12 : /*******************************************************************************/
13 : /****************** THESE FUNCTIONS MAY NOT BE THREAD SAFE *********************/
14 : /*******************************************************************************/
15 : /*******************************************************************************/
16 :
17 : PR_BEGIN_EXTERN_C
18 :
19 : /*
20 : ** PR_GetEnv() -- Retrieve value of environment variable
21 : **
22 : ** Description:
23 : ** PR_GetEnv() is modeled on Unix getenv().
24 : **
25 : **
26 : ** Inputs:
27 : ** var -- The name of the environment variable
28 : **
29 : ** Returns:
30 : ** The value of the environment variable 'var' or NULL if
31 : ** the variable is undefined.
32 : **
33 : ** Restrictions:
34 : ** You'd think that a POSIX getenv(), putenv() would be
35 : ** consistently implemented everywhere. Surprise! It is not. On
36 : ** some platforms, a putenv() where the argument is of
37 : ** the form "name" causes the named environment variable to
38 : ** be un-set; that is: a subsequent getenv() returns NULL. On
39 : ** other platforms, the putenv() fails, on others, it is a
40 : ** no-op. Similarly, a putenv() where the argument is of the
41 : ** form "name=" causes the named environment variable to be
42 : ** un-set; a subsequent call to getenv() returns NULL. On
43 : ** other platforms, a subsequent call to getenv() returns a
44 : ** pointer to a null-string (a byte of zero).
45 : **
46 : ** PR_GetEnv(), PR_SetEnv() provide a consistent behavior
47 : ** across all supported platforms. There are, however, some
48 : ** restrictions and some practices you must use to achieve
49 : ** consistent results everywhere.
50 : **
51 : ** When manipulating the environment there is no way to un-set
52 : ** an environment variable across all platforms. We suggest
53 : ** you interpret the return of a pointer to null-string to
54 : ** mean the same as a return of NULL from PR_GetEnv().
55 : **
56 : ** A call to PR_SetEnv() where the parameter is of the form
57 : ** "name" will return PR_FAILURE; the environment remains
58 : ** unchanged. A call to PR_SetEnv() where the parameter is
59 : ** of the form "name=" may un-set the envrionment variable on
60 : ** some platforms; on others it may set the value of the
61 : ** environment variable to the null-string.
62 : **
63 : ** For example, to test for NULL return or return of the
64 : ** null-string from PR_GetEnv(), use the following code
65 : ** fragment:
66 : **
67 : ** char *val = PR_GetEnv("foo");
68 : ** if ((NULL == val) || ('\0' == *val)) {
69 : ** ... interpret this as un-set ...
70 : ** }
71 : **
72 : ** The caller must ensure that the string passed
73 : ** to PR_SetEnv() is persistent. That is: The string should
74 : ** not be on the stack, where it can be overwritten
75 : ** on return from the function calling PR_SetEnv().
76 : ** Similarly, the string passed to PR_SetEnv() must not be
77 : ** overwritten by other actions of the process. ... Some
78 : ** platforms use the string by reference rather than copying
79 : ** it into the environment space. ... You have been warned!
80 : **
81 : ** Use of platform-native functions that manipulate the
82 : ** environment (getenv(), putenv(),
83 : ** SetEnvironmentVariable(), etc.) must not be used with
84 : ** NSPR's similar functions. The platform-native functions
85 : ** may not be thread safe and/or may operate on different
86 : ** conceptual environment space than that operated upon by
87 : ** NSPR's functions or other environment manipulating
88 : ** functions on the same platform. (!)
89 : **
90 : */
91 1359 : NSPR_API(char*) PR_GetEnv(const char *var);
92 :
93 : /*
94 : ** PR_GetEnvSecure() -- get a security-sensitive environment variable
95 : **
96 : ** Description:
97 : **
98 : ** PR_GetEnvSecure() is similar to PR_GetEnv(), but it returns NULL if
99 : ** the program was run with elevated privilege (e.g., setuid or setgid
100 : ** on Unix). This can be used for cases like log file paths which
101 : ** could otherwise be used for privilege escalation. Note that some
102 : ** platforms may have platform-specific privilege elevation mechanisms
103 : ** not recognized by this function; see the implementation for details.
104 : */
105 42 : NSPR_API(char*) PR_GetEnvSecure(const char *var);
106 :
107 : /*
108 : ** PR_SetEnv() -- set, unset or change an environment variable
109 : **
110 : ** Description:
111 : ** PR_SetEnv() is modeled on the Unix putenv() function.
112 : **
113 : ** Inputs:
114 : ** string -- pointer to a caller supplied
115 : ** constant, persistent string of the form name=value. Where
116 : ** name is the name of the environment variable to be set or
117 : ** changed; value is the value assigned to the variable.
118 : **
119 : ** Returns:
120 : ** PRStatus.
121 : **
122 : ** Restrictions:
123 : ** See the Restrictions documented in the description of
124 : ** PR_GetEnv() in this header file.
125 : **
126 : **
127 : */
128 15 : NSPR_API(PRStatus) PR_SetEnv(const char *string);
129 :
130 : /*
131 : ** PR_DuplicateEnvironment() -- Obtain a copy of the environment.
132 : **
133 : ** Description:
134 : ** PR_DuplicateEnvironment() copies the environment so that it can be
135 : ** modified without changing the current process's environment, and
136 : ** then passed to interfaces such as POSIX execve(). In particular,
137 : ** this avoids needing to allocate memory or take locks in the child
138 : ** after a fork(); neither of these is allowed by POSIX after a
139 : ** multithreaded process calls fork(), and PR_SetEnv does both.
140 : **
141 : ** Inputs:
142 : ** none
143 : **
144 : ** Returns:
145 : ** A pointer to a null-terminated array of null-terminated strings,
146 : ** like the traditional global variable "environ". The array and
147 : ** the strings are allocated with PR_Malloc(), and it is the
148 : ** caller's responsibility to free them.
149 : **
150 : ** In case of memory allocation failure, or if the operating system
151 : ** doesn't support reading the entire environment through the global
152 : ** variable "environ" or similar, returns NULL instead.
153 : **
154 : ** Restrictions:
155 : ** Similarly to PR_GetEnv(), this function may not interoperate as
156 : ** expected with the operating system's native environment accessors.
157 : */
158 3 : NSPR_API(char **) PR_DuplicateEnvironment(void);
159 :
160 : PR_END_EXTERN_C
161 :
162 : #endif /* prenv_h___ */
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