изменить или добавить переменную среды (change or add an environment variable)
Имя (Name)
putenv - change or add an environment variable
Синопсис (Synopsis)
#include <stdlib.h>
int putenv(char *string);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
putenv():
_XOPEN_SOURCE
|| /* Glibc since 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _SVID_SOURCE
Описание (Description)
The putenv() function adds or changes the value of environment
variables. The argument string is of the form name=value. If
name does not already exist in the environment, then string is
added to the environment. If name does exist, then the value of
name in the environment is changed to value. The string pointed
to by string becomes part of the environment, so altering the
string changes the environment.
Возвращаемое значение (Return value)
The putenv() function returns zero on success. On failure, it
returns a nonzero value, and errno is set to indicate the error.
Ошибки (Error)
ENOMEM Insufficient space to allocate new environment.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────┬───────────────┬─────────────────────┐
│Interface │ Attribute │ Value │
├──────────────────────────┼───────────────┼─────────────────────┤
│putenv() │ Thread safety │ MT-Unsafe const:env │
└──────────────────────────┴───────────────┴─────────────────────┘
Стандарты (Conforming to)
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
Примечание (Note)
The putenv() function is not required to be reentrant, and the
one in glibc 2.0 is not, but the glibc 2.1 version is.
Since version 2.1.2, the glibc implementation conforms to SUSv2:
the pointer string given to putenv() is used. In particular,
this string becomes part of the environment; changing it later
will change the environment. (Thus, it is an error to call
putenv() with an automatic variable as the argument, then return
from the calling function while string is still part of the
environment.) However, glibc versions 2.0 to 2.1.1 differ: a
copy of the string is used. On the one hand this causes a memory
leak, and on the other hand it violates SUSv2.
The 4.4BSD version, like glibc 2.0, uses a copy.
SUSv2 removes the const from the prototype, and so does glibc
2.1.3.
The GNU C library implementation provides a nonstandard
extension. If string does not include an equal sign:
putenv("NAME");
then the named variable is removed from the caller's environment.
Смотри также (See also)
clearenv(3), getenv(3), setenv(3), unsetenv(3), environ(7)
