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

20       The unsetenv() function shall remove an environment variable  from  the
21       environment  of  the  calling  process.  The  name argument points to a
22       string, which is the name of the variable  to  be  removed.  The  named
23       argument shall not contain an '=' character. If the named variable does
24       not  exist  in  the  current  environment,  the  environment  shall  be
25       unchanged  and  the  function  is considered to have completed success‐
26       fully.
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28       The unsetenv() function shall update the list of pointers to which env‐
29       iron points.
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31       The unsetenv() function need not be thread-safe.
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RETURN VALUE

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

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

47       None.
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APPLICATION USAGE

50       None.
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RATIONALE

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

56       None.
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SEE ALSO

59       getenv(), setenv()
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61       The Base Definitions volume of POSIX.1‐2017, <stdlib.h>, <sys_types.h>
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64       Portions of this text are reprinted and reproduced in  electronic  form
65       from  IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
66       table Operating System Interface (POSIX), The Open Group Base  Specifi‐
67       cations  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of
68       Electrical and Electronics Engineers, Inc and The Open Group.   In  the
69       event of any discrepancy between this version and the original IEEE and
70       The Open Group Standard, the original IEEE and The Open Group  Standard
71       is  the  referee document. The original Standard can be obtained online
72       at http://www.opengroup.org/unix/online.html .
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74       Any typographical or formatting errors that appear  in  this  page  are
75       most likely to have been introduced during the conversion of the source
76       files to man page format. To report such errors,  see  https://www.ker‐
77       nel.org/doc/man-pages/reporting_bugs.html .
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81IEEE/The Open Group                  2017                         UNSETENV(3P)
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