Quelle prenv.h
Sprache: C
/* 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 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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