Originální popis anglicky:
unsetenv - remove an environment variable
Návod, kniha: POSIX Programmer's Manual
#include <stdlib.h>
int unsetenv(const char *
name);
The
unsetenv() function shall remove an environment variable from the
environment of the calling process. The
name argument points to a
string, which is the name of the variable to be removed. The named argument
shall not contain an
'=' character. If the named variable does not
exist in the current environment, the environment shall be unchanged and the
function is considered to have completed successfully.
If the application modifies
environ or the pointers to which it points,
the behavior of
unsetenv() is undefined. The
unsetenv() function
shall update the list of pointers to which
environ points.
The
unsetenv() function need not be reentrant. A function that is not
required to be reentrant is not required to be thread-safe.
Upon successful completion, zero shall be returned. Otherwise, -1 shall be
returned,
errno set to indicate the error, and the environment shall be
unchanged.
The
unsetenv() function shall fail if:
- EINVAL
- The name argument is a null pointer, points to an
empty string, or points to a string containing an '=' character.
The following sections are informative.
None.
None.
Refer to the RATIONALE section in
setenv() .
None.
getenv() ,
setenv() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<stdlib.h>,
<sys/types.h>,
<unistd.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
