93 lines
3.2 KiB
C++
93 lines
3.2 KiB
C++
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/*
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* setenv.c
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*
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* Implementation of POSIX standard IEEE 1003.1-2008 setenv() function;
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* may also be invoked inline, as "retval = setenv( varname, NULL, 1 )",
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* to implement the complementary unsetenv() function.
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*
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* $Id$
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*
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* Written by Keith Marshall <keithmarshall@users.sourceforge.net>
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* Copyright (C) 2016, MinGW.org Project
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*
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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int setenv( const char *var, const char *value, int overwrite )
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{
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/* Core implementation for both setenv() and unsetenv() functions;
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* at the outset, assume that the requested operation may fail.
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*/
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int retval = -1;
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/* The specified "var" name MUST be non-NULL, not a zero-length
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* string, and must not include any '=' character.
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*/
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if( var && *var && (strchr( var, '=' ) == NULL) )
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{
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/* A properly named variable may be added to, removed from,
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* or modified within the environment, ONLY if "overwrite"
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* mode is enabled, OR if the named variable does not yet
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* exist...
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*/
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if( overwrite || getenv( var ) == NULL )
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{
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/* ... in which cases, we convert the specified name and
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* value into the appropriate form for use with putenv(),
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* (noting that we accept a NULL "value" as equivalent to
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* a zero-length string, which renders putenv() as the
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* equivalent of unsetenv()).
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*/
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const char *fmt = "%s=%s";
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const char *val = value ? value : "";
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char buf[1 + snprintf( NULL, 0, fmt, var, val )];
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snprintf( buf, sizeof( buf ), fmt, var, val );
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if( (retval = putenv( buf )) != 0 )
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/*
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* If putenv() returns non-zero, indicating failure, the
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* most probable explanation is that there wasn't enough
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* free memory; ensure that errno is set accordingly.
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*/
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errno = ENOMEM;
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}
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else
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/* The named variable already exists, and overwrite mode
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* was not enabled; there is nothing to be done.
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*/
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retval = 0;
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}
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else
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/* The specified environment variable name was invalid.
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*/
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errno = EINVAL;
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/* Succeed or fail, "retval" has now been set to indicate the
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* appropriate status for return.
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*/
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return retval;
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}
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