| /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ |
| /* This Source Code Form is subject to the terms of the Mozilla Public |
| * License, v. 2.0. If a copy of the MPL was not distributed with this |
| * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ |
| |
| #ifndef prenv_h___ |
| #define prenv_h___ |
| |
| #include "prtypes.h" |
| |
| /*******************************************************************************/ |
| /*******************************************************************************/ |
| /****************** THESE FUNCTIONS MAY NOT BE THREAD SAFE *********************/ |
| /*******************************************************************************/ |
| /*******************************************************************************/ |
| |
| PR_BEGIN_EXTERN_C |
| |
| /* |
| ** PR_GetEnv() -- Retrieve value of environment variable |
| ** |
| ** Description: |
| ** PR_GetEnv() is modeled on Unix getenv(). |
| ** |
| ** |
| ** Inputs: |
| ** var -- The name of the environment variable |
| ** |
| ** Returns: |
| ** The value of the environment variable 'var' or NULL if |
| ** the variable is undefined. |
| ** |
| ** Restrictions: |
| ** You'd think that a POSIX getenv(), putenv() would be |
| ** consistently implemented everywhere. Surprise! It is not. On |
| ** some platforms, a putenv() where the argument is of |
| ** the form "name" causes the named environment variable to |
| ** be un-set; that is: a subsequent getenv() returns NULL. On |
| ** other platforms, the putenv() fails, on others, it is a |
| ** no-op. Similarly, a putenv() where the argument is of the |
| ** form "name=" causes the named environment variable to be |
| ** un-set; a subsequent call to getenv() returns NULL. On |
| ** other platforms, a subsequent call to getenv() returns a |
| ** pointer to a null-string (a byte of zero). |
| ** |
| ** PR_GetEnv(), PR_SetEnv() provide a consistent behavior |
| ** across all supported platforms. There are, however, some |
| ** restrictions and some practices you must use to achieve |
| ** consistent results everywhere. |
| ** |
| ** When manipulating the environment there is no way to un-set |
| ** an environment variable across all platforms. We suggest |
| ** you interpret the return of a pointer to null-string to |
| ** mean the same as a return of NULL from PR_GetEnv(). |
| ** |
| ** A call to PR_SetEnv() where the parameter is of the form |
| ** "name" will return PR_FAILURE; the environment remains |
| ** unchanged. A call to PR_SetEnv() where the parameter is |
| ** of the form "name=" may un-set the envrionment variable on |
| ** some platforms; on others it may set the value of the |
| ** environment variable to the null-string. |
| ** |
| ** For example, to test for NULL return or return of the |
| ** null-string from PR_GetEnv(), use the following code |
| ** fragment: |
| ** |
| ** char *val = PR_GetEnv("foo"); |
| ** if ((NULL == val) || ('\0' == *val)) { |
| ** ... interpret this as un-set ... |
| ** } |
| ** |
| ** The caller must ensure that the string passed |
| ** to PR_SetEnv() is persistent. That is: The string should |
| ** not be on the stack, where it can be overwritten |
| ** on return from the function calling PR_SetEnv(). |
| ** Similarly, the string passed to PR_SetEnv() must not be |
| ** overwritten by other actions of the process. ... Some |
| ** platforms use the string by reference rather than copying |
| ** it into the environment space. ... You have been warned! |
| ** |
| ** Use of platform-native functions that manipulate the |
| ** environment (getenv(), putenv(), |
| ** SetEnvironmentVariable(), etc.) must not be used with |
| ** NSPR's similar functions. The platform-native functions |
| ** may not be thread safe and/or may operate on different |
| ** conceptual environment space than that operated upon by |
| ** NSPR's functions or other environment manipulating |
| ** functions on the same platform. (!) |
| ** |
| */ |
| NSPR_API(char*) PR_GetEnv(const char *var); |
| |
| /* |
| ** PR_GetEnvSecure() -- get a security-sensitive environment variable |
| ** |
| ** Description: |
| ** |
| ** PR_GetEnvSecure() is similar to PR_GetEnv(), but it returns NULL if |
| ** the program was run with elevated privilege (e.g., setuid or setgid |
| ** on Unix). This can be used for cases like log file paths which |
| ** could otherwise be used for privilege escalation. Note that some |
| ** platforms may have platform-specific privilege elevation mechanisms |
| ** not recognized by this function; see the implementation for details. |
| */ |
| NSPR_API(char*) PR_GetEnvSecure(const char *var); |
| |
| /* |
| ** PR_SetEnv() -- set, unset or change an environment variable |
| ** |
| ** Description: |
| ** PR_SetEnv() is modeled on the Unix putenv() function. |
| ** |
| ** Inputs: |
| ** string -- pointer to a caller supplied |
| ** constant, persistent string of the form name=value. Where |
| ** name is the name of the environment variable to be set or |
| ** changed; value is the value assigned to the variable. |
| ** |
| ** Returns: |
| ** PRStatus. |
| ** |
| ** Restrictions: |
| ** See the Restrictions documented in the description of |
| ** PR_GetEnv() in this header file. |
| ** |
| ** |
| */ |
| NSPR_API(PRStatus) PR_SetEnv(const char *string); |
| |
| /* |
| ** PR_DuplicateEnvironment() -- Obtain a copy of the environment. |
| ** |
| ** Description: |
| ** PR_DuplicateEnvironment() copies the environment so that it can be |
| ** modified without changing the current process's environment, and |
| ** then passed to interfaces such as POSIX execve(). In particular, |
| ** this avoids needing to allocate memory or take locks in the child |
| ** after a fork(); neither of these is allowed by POSIX after a |
| ** multithreaded process calls fork(), and PR_SetEnv does both. |
| ** |
| ** Inputs: |
| ** none |
| ** |
| ** Returns: |
| ** A pointer to a null-terminated array of null-terminated strings, |
| ** like the traditional global variable "environ". The array and |
| ** the strings are allocated with PR_Malloc(), and it is the |
| ** caller's responsibility to free them. |
| ** |
| ** In case of memory allocation failure, or if the operating system |
| ** doesn't support reading the entire environment through the global |
| ** variable "environ" or similar, returns NULL instead. |
| ** |
| ** Restrictions: |
| ** Similarly to PR_GetEnv(), this function may not interoperate as |
| ** expected with the operating system's native environment accessors. |
| */ |
| NSPR_API(char **) PR_DuplicateEnvironment(void); |
| |
| PR_END_EXTERN_C |
| |
| #endif /* prenv_h___ */ |