man3p/unsetenv.3p

   1 .\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
   2 .TH "UNSETENV" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
   3 .\" unsetenv
   4 .SH NAME
   5 unsetenv \- remove an environment variable
   6 .SH SYNOPSIS
   7 .LP
   8 \fB#include <stdlib.h>
   9 .br
  10 .sp
  11 int unsetenv(const char *\fP\fIname\fP\fB); \fP
  12 \fB
  13 .br
  14 \fP
  15 .SH DESCRIPTION
  16 .LP
  17 The \fIunsetenv\fP() function shall remove an environment variable
  18 from the environment of the calling process. The \fIname\fP
  19 argument points to a string, which is the name of the variable to
  20 be removed. The named argument shall not contain an \fB'='\fP
  21 character. If the named variable does not exist in the current environment,
  22 the environment shall be unchanged and the function is
  23 considered to have completed successfully.
  24 .LP
  25 If the application modifies \fIenviron\fP or the pointers to which
  26 it points, the behavior of \fIunsetenv\fP() is undefined.
  27 The \fIunsetenv\fP() function shall update the list of pointers to
  28 which \fIenviron\fP points.
  29 .LP
  30 The \fIunsetenv\fP() function need not be reentrant. A function that
  31 is not required to be reentrant is not required to be
  32 thread-safe.
  33 .SH RETURN VALUE
  34 .LP
  35 Upon successful completion, zero shall be returned. Otherwise, -1
  36 shall be returned, \fIerrno\fP set to indicate the error, and
  37 the environment shall be unchanged.
  38 .SH ERRORS
  39 .LP
  40 The \fIunsetenv\fP() function shall fail if:
  41 .TP 7
  42 .B EINVAL
  43 The \fIname\fP argument is a null pointer, points to an empty string,
  44 or points to a string containing an \fB'='\fP
  45 character.
  46 .sp
  47 .LP
  48 \fIThe following sections are informative.\fP
  49 .SH EXAMPLES
  50 .LP
  51 None.
  52 .SH APPLICATION USAGE
  53 .LP
  54 None.
  55 .SH RATIONALE
  56 .LP
  57 Refer to the RATIONALE section in \fIsetenv\fP() .
  58 .SH FUTURE DIRECTIONS
  59 .LP
  60 None.
  61 .SH SEE ALSO
  62 .LP
  63 \fIgetenv\fP() , \fIsetenv\fP() , the Base Definitions volume of
  64 IEEE\ Std\ 1003.1-2001, \fI<stdlib.h>\fP, \fI<sys/types.h>\fP, \fI<unistd.h>\fP
  65 .SH COPYRIGHT
  66 Portions of this text are reprinted and reproduced in electronic form
  67 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
  68 -- Portable Operating System Interface (POSIX), The Open Group Base
  69 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
  70 Electrical and Electronics Engineers, Inc and The Open Group. 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 at
  74 http://www.opengroup.org/unix/online.html .