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
17PR_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*/
91NSPR_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*/
105NSPR_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*/
128NSPR_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*/
158NSPR_API(char **) PR_DuplicateEnvironment(void);
159
160PR_END_EXTERN_C
161
162#endif /* prenv_h___ */
163

source code of include/nspr/prenv.h