1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* 3 * The contents of this file are subject to the Mozilla Public 4 * License Version 1.1 (the "License"); you may not use this file 5 * except in compliance with the License. You may obtain a copy of 6 * the License at http://www.mozilla.org/MPL/ 7 * 8 * Software distributed under the License is distributed on an "AS 9 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or 10 * implied. See the License for the specific language governing 11 * rights and limitations under the License. 12 * 13 * The Original Code is the Netscape Portable Runtime (NSPR). 14 * 15 * The Initial Developer of the Original Code is Netscape 16 * Communications Corporation. Portions created by Netscape are 17 * Copyright (C) 1998-2000 Netscape Communications Corporation. All 18 * Rights Reserved. 19 * 20 * Contributor(s): 21 * 22 * Alternatively, the contents of this file may be used under the 23 * terms of the GNU General Public License Version 2 or later (the 24 * "GPL"), in which case the provisions of the GPL are applicable 25 * instead of those above. If you wish to allow use of your 26 * version of this file only under the terms of the GPL and not to 27 * allow others to use your version of this file under the MPL, 28 * indicate your decision by deleting the provisions above and 29 * replace them with the notice and other provisions requiored by 30 * the GPL. If you do not delete the provisions above, a recipient 31 * may use your version of this file under either the MPL or the 32 * GPL. 33 */ 34 35 #ifndef prenv_h___ 36 #define prenv_h___ 37 38 #include "prtypes.h" 39 40 /*******************************************************************************/ 41 /*******************************************************************************/ 42 /****************** THESE FUNCTIONS MAY NOT BE THREAD SAFE *********************/ 43 /*******************************************************************************/ 44 /*******************************************************************************/ 45 46 PR_BEGIN_EXTERN_C 47 48 /* 49 ** PR_GetEnv() -- Retrieve value of environment variable 50 ** 51 ** Description: 52 ** PR_GetEnv() is modeled on Unix getenv(). 53 ** 54 ** 55 ** Inputs: 56 ** var -- The name of the environment variable 57 ** 58 ** Returns: 59 ** The value of the environment variable 'var' or NULL if 60 ** the variable is undefined. 61 ** 62 ** Restrictions: 63 ** You'd think that a POSIX getenv(), putenv() would be 64 ** consistently implemented everywhere. Surprise! It is not. On 65 ** some platforms, a putenv() where the argument is of 66 ** the form "name" causes the named environment variable to 67 ** be un-set; that is: a subsequent getenv() returns NULL. On 68 ** other platforms, the putenv() fails, on others, it is a 69 ** no-op. Similarly, a putenv() where the argument is of the 70 ** form "name=" causes the named environment variable to be 71 ** un-set; a subsequent call to getenv() returns NULL. On 72 ** other platforms, a subsequent call to getenv() returns a 73 ** pointer to a null-string (a byte of zero). 74 ** 75 ** PR_GetEnv(), PR_SetEnv() provide a consistent behavior 76 ** across all supported platforms. There are, however, some 77 ** restrictions and some practices you must use to achieve 78 ** consistent results everywhere. 79 ** 80 ** When manipulating the environment there is no way to un-set 81 ** an environment variable across all platforms. We suggest 82 ** you interpret the return of a pointer to null-string to 83 ** mean the same as a return of NULL from PR_GetEnv(). 84 ** 85 ** A call to PR_SetEnv() where the parameter is of the form 86 ** "name" will return PR_FAILURE; the environment remains 87 ** unchanged. A call to PR_SetEnv() where the parameter is 88 ** of the form "name=" may un-set the envrionment variable on 89 ** some platforms; on others it may set the value of the 90 ** environment variable to the null-string. 91 ** 92 ** For example, to test for NULL return or return of the 93 ** null-string from PR_GetEnv(), use the following code 94 ** fragment: 95 ** 96 ** char *val = PR_GetEnv("foo"); 97 ** if ((NULL == val) || ('\0' == *val)) { 98 ** ... interpret this as un-set ... 99 ** } 100 ** 101 ** The caller must ensure that the string passed 102 ** to PR_SetEnv() is persistent. That is: The string should 103 ** not be on the stack, where it can be overwritten 104 ** on return from the function calling PR_SetEnv(). 105 ** Similarly, the string passed to PR_SetEnv() must not be 106 ** overwritten by other actions of the process. ... Some 107 ** platforms use the string by reference rather than copying 108 ** it into the environment space. ... You have been warned! 109 ** 110 ** Use of platform-native functions that manipulate the 111 ** environment (getenv(), putenv(), 112 ** SetEnvironmentVariable(), etc.) must not be used with 113 ** NSPR's similar functions. The platform-native functions 114 ** may not be thread safe and/or may operate on different 115 ** conceptual environment space than that operated upon by 116 ** NSPR's functions or other environment manipulating 117 ** functions on the same platform. (!) 118 ** 119 */ 120 NSPR_API(char*) PR_GetEnv(const char *var); 121 122 /* 123 ** PR_SetEnv() -- set, unset or change an environment variable 124 ** 125 ** Description: 126 ** PR_SetEnv() is modeled on the Unix putenv() function. 127 ** 128 ** Inputs: 129 ** string -- pointer to a caller supplied 130 ** constant, persistent string of the form name=value. Where 131 ** name is the name of the environment variable to be set or 132 ** changed; value is the value assigned to the variable. 133 ** 134 ** Returns: 135 ** PRStatus. 136 ** 137 ** Restrictions: 138 ** See the Restrictions documented in the description of 139 ** PR_GetEnv() in this header file. 140 ** 141 ** 142 */ 143 NSPR_API(PRStatus) PR_SetEnv(const char *string); 144 145 /* 146 ** DEPRECATED. Use PR_SetEnv() instead. 147 */ 148 #ifdef XP_MAC 149 NSPR_API(PRIntn) PR_PutEnv(const char *string); 150 #endif 151 152 PR_END_EXTERN_C 153 154 #endif /* prenv_h___ */ 155
