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/* -*- 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___ */
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