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comparison: nsprpub/pr/include/prenv.h
nsprpub/pr/include/prenv.h
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- TOR_BUG_9701
- changeset 13
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| -1:000000000000 | 0:55874e44dd67 |
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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 NSPR_API(char*) PR_GetEnv(const char *var); | |
| 92 | |
| 93 /* | |
| 94 ** PR_SetEnv() -- set, unset or change an environment variable | |
| 95 ** | |
| 96 ** Description: | |
| 97 ** PR_SetEnv() is modeled on the Unix putenv() function. | |
| 98 ** | |
| 99 ** Inputs: | |
| 100 ** string -- pointer to a caller supplied | |
| 101 ** constant, persistent string of the form name=value. Where | |
| 102 ** name is the name of the environment variable to be set or | |
| 103 ** changed; value is the value assigned to the variable. | |
| 104 ** | |
| 105 ** Returns: | |
| 106 ** PRStatus. | |
| 107 ** | |
| 108 ** Restrictions: | |
| 109 ** See the Restrictions documented in the description of | |
| 110 ** PR_GetEnv() in this header file. | |
| 111 ** | |
| 112 ** | |
| 113 */ | |
| 114 NSPR_API(PRStatus) PR_SetEnv(const char *string); | |
| 115 | |
| 116 PR_END_EXTERN_C | |
| 117 | |
| 118 #endif /* prenv_h___ */ |
