1UNSETENV(P)                POSIX Programmer's Manual               UNSETENV(P)
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NAME

6       unsetenv - remove an environment variable
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SYNOPSIS

9       #include <stdlib.h>
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11       int unsetenv(const char *name);
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DESCRIPTION

15       The  unsetenv()  function shall remove an environment variable from the
16       environment of the calling process.  The  name  argument  points  to  a
17       string,  which  is  the  name  of the variable to be removed. The named
18       argument shall not contain an '=' character. If the named variable does
19       not  exist  in  the  current  environment,  the  environment  shall  be
20       unchanged and the function is considered  to  have  completed  success‐
21       fully.
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23       If the application modifies environ or the pointers to which it points,
24       the behavior of unsetenv() is undefined.  The unsetenv() function shall
25       update the list of pointers to which environ points.
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27       The  unsetenv()  function need not be reentrant. A function that is not
28       required to be reentrant is not required to be thread-safe.
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RETURN VALUE

31       Upon successful completion, zero shall be returned. Otherwise, -1 shall
32       be returned, errno set to indicate the error, and the environment shall
33       be unchanged.
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ERRORS

36       The unsetenv() function shall fail if:
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38       EINVAL The name argument is a null pointer, points to an empty  string,
39              or points to a string containing an '=' character.
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42       The following sections are informative.
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EXAMPLES

45       None.
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APPLICATION USAGE

48       None.
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RATIONALE

51       Refer to the RATIONALE section in setenv() .
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FUTURE DIRECTIONS

54       None.
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SEE ALSO

57       getenv()    ,    setenv()    ,   the   Base   Definitions   volume   of
58       IEEE Std 1003.1-2001, <stdlib.h>, <sys/types.h>, <unistd.h>
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61       Portions of this text are reprinted and reproduced in  electronic  form
62       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
63       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
64       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
65       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
66       event of any discrepancy between this version and the original IEEE and
67       The Open Group Standard, the original IEEE and The Open Group  Standard
68       is  the  referee document. The original Standard can be obtained online
69       at http://www.opengroup.org/unix/online.html .
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73IEEE/The Open Group                  2003                          UNSETENV(P)
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