очистить окружающую среду (clear the environment)
Имя (Name)
clearenv - clear the environment
Синопсис (Synopsis)
#include <stdlib.h>
int clearenv(void);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
clearenv():
/* Glibc since 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
Описание (Description)
The clearenv() function clears the environment of all name-value
pairs and sets the value of the external variable environ to
NULL. After this call, new variables can be added to the
environment using putenv(3) and setenv(3).
Возвращаемое значение (Return value)
The clearenv() function returns zero on success, and a nonzero
value on failure.
Версии (Versions)
Available since glibc 2.0.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────┬───────────────┬─────────────────────┐
│Interface │ Attribute │ Value │
├──────────────────────────┼───────────────┼─────────────────────┤
│clearenv() │ Thread safety │ MT-Unsafe const:env │
└──────────────────────────┴───────────────┴─────────────────────┘
Стандарты (Conforming to)
Various UNIX variants (DG/UX, HP-UX, QNX, ...). POSIX.9
(bindings for FORTRAN77). POSIX.1-1996 did not accept clearenv()
and putenv(3), but changed its mind and scheduled these functions
for some later issue of this standard (see §B.4.6.1). However,
POSIX.1-2001 adds only putenv(3), and rejected clearenv().
Примечание (Note)
On systems where clearenv() is unavailable, the assignment
environ = NULL;
will probably do.
The clearenv() function may be useful in security-conscious
applications that want to precisely control the environment that
is passed to programs executed using exec(3). The application
would do this by first clearing the environment and then adding
select environment variables.
Note that the main effect of clearenv() is to adjust the value of
the pointer environ(7); this function does not erase the contents
of the buffers containing the environment definitions.
The DG/UX and Tru64 man pages write: If environ has been modified
by anything other than the putenv(3), getenv(3), or clearenv()
functions, then clearenv() will return an error and the process
environment will remain unchanged.
Смотри также (See also)
getenv(3), putenv(3), setenv(3), unsetenv(3), environ(7)
