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

13       unsetenv — remove an environment variable
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SYNOPSIS

16       #include <stdlib.h>
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18       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       The unsetenv() function shall update the list of pointers to which env‐
30       iron points.
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32       The unsetenv() function need not be thread-safe.
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RETURN VALUE

35       Upon successful completion, zero shall be returned. Otherwise, −1 shall
36       be returned, errno set to indicate the error, and the environment shall
37       be unchanged.
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ERRORS

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

48       None.
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APPLICATION USAGE

51       None.
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RATIONALE

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

57       None.
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SEE ALSO

60       getenv(), setenv()
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62       The Base Definitions volume of POSIX.1‐2008, <stdlib.h>, <sys_types.h>
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65       Portions of this text are reprinted and reproduced in  electronic  form
66       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
67       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
68       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
69       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
70       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
71       event of any discrepancy between this version and the original IEEE and
72       The  Open Group Standard, the original IEEE and The Open Group Standard
73       is the referee document. The original Standard can be  obtained  online
74       at http://www.unix.org/online.html .
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76       Any  typographical  or  formatting  errors that appear in this page are
77       most likely to have been introduced during the conversion of the source
78       files  to  man page format. To report such errors, see https://www.ker‐
79       nel.org/doc/man-pages/reporting_bugs.html .
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83IEEE/The Open Group                  2013                         UNSETENV(3P)
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