User  |  Syst  |  Libr  |  Device  |  Files  |  Other  |  Admin  |  Head  |

---

   unsetenv    ( 3 )

---

---

Имя (Name)

setenv - change or add an environment variable

---

Синопсис (Synopsis)

#include <stdlib.h>

       int setenv(const char *name, const char *value, int overwrite);
       int unsetenv(const char *name);

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       setenv(), unsetenv():
           _POSIX_C_SOURCE >= 200112L
               || /* Glibc <= 2.19: */ _BSD_SOURCE

---

Описание (Description)

The setenv() function adds the variable name to the environment
       with the value value, if name does not already exist.  If name
       does exist in the environment, then its value is changed to value
       if overwrite is nonzero; if overwrite is zero, then the value of
       name is not changed (and setenv() returns a success status).
       This function makes copies of the strings pointed to by name and
       value (by contrast with putenv(3)).

       The unsetenv() function deletes the variable name from the
       environment.  If name does not exist in the environment, then the
       function succeeds, and the environment is unchanged.

---

Возвращаемое значение (Return value)

setenv() and unsetenv() functions return zero on success, or -1
       on error, with errno set to indicate the error.

---

Ошибки (Error)

EINVAL name is NULL, points to a string of length 0, or contains
              an '=' character.

       ENOMEM Insufficient memory to add a new variable to the
              environment.

---

Атрибуты (Attributes)

For an explanation of the terms used in this section, see
       attributes(7).

       ┌──────────────────────────┬───────────────┬─────────────────────┐
       │Interface                 │ Attribute     │ Value               │
       ├──────────────────────────┼───────────────┼─────────────────────┤
       │setenv(), unsetenv()      │ Thread safety │ MT-Unsafe const:env │
       └──────────────────────────┴───────────────┴─────────────────────┘

---

Стандарты (Conforming to)

POSIX.1-2001, POSIX.1-2008, 4.3BSD.

---

Примечание (Note)

POSIX.1 does not require setenv() or unsetenv() to be reentrant.

       Prior to glibc 2.2.2, unsetenv() was prototyped as returning
       void; more recent glibc versions follow the POSIX.1-compliant
       prototype shown in the SYNOPSIS.

---

Ошибки (баги) (Bugs)

POSIX.1 specifies that if name contains an '=' character, then
       setenv() should fail with the error EINVAL; however, versions of
       glibc before 2.3.4 allowed an '=' sign in name.

---

Смотри также (See also)

clearenv(3), getenv(3), putenv(3), environ(7)

---