1UNSETENV(3P)               POSIX Programmer's Manual              UNSETENV(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       unsetenv - remove an environment variable
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SYNOPSIS

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

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

37       Upon successful completion, zero shall be returned. Otherwise, -1 shall
38       be returned, errno set to indicate the error, and the environment shall
39       be unchanged.
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ERRORS

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

51       None.
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APPLICATION USAGE

54       None.
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RATIONALE

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

60       None.
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SEE ALSO

63       getenv(),    setenv(),    the    Base     Definitions     volume     of
64       IEEE Std 1003.1-2001, <stdlib.h>, <sys/types.h>, <unistd.h>
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67       Portions  of  this text are reprinted and reproduced in electronic form
68       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
69       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
70       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
71       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
72       event of any discrepancy between this version and the original IEEE and
73       The  Open Group Standard, the original IEEE and The Open Group Standard
74       is the referee document. The original Standard can be  obtained  online
75       at http://www.opengroup.org/unix/online.html .
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79IEEE/The Open Group                  2003                         UNSETENV(3P)
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