79 lines
2.2 KiB
C
79 lines
2.2 KiB
C
/*
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* Copyright (c) 2014 Jonas 'Sortie' Termansen.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* stdlib/unsetenv.c
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* Unset an environment variable.
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*/
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#include <errno.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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static inline
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bool matches_environment_variable(const char* what,
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const char* name, size_t name_length)
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{
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return !strncmp(what, name, name_length) && what[name_length] == '=';
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}
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int unsetenv(const char* name)
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{
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if ( !name )
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return errno = EINVAL, -1;
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if ( !name[0] )
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return errno = EINVAL, -1;
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// Verify the name doesn't contain a '=' character.
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size_t name_length = 0;
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while ( name[name_length] )
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if ( name[name_length++] == '=' )
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return errno = EINVAL, -1;
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if ( !environ )
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return 0;
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// Delete all variables from the environment with the given name.
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for ( size_t i = 0; environ[i]; i++ )
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{
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if ( matches_environment_variable(environ[i], name, name_length) )
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{
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// Free the string and move the array around in constant time if
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// the setenv implementation is in control of the array.
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if ( environ == __environ_malloced )
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{
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free(environ[i]);
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environ[i] = environ[__environ_used-1];
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environ[--__environ_used] = NULL;
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}
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// Otherwise, we'll simply clear that entry in environ, but we can't
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// do it in constant time as we don't know how large the array is.
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else
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{
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for ( size_t n = i; environ[n]; n++ )
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environ[n] = environ[n+1];
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}
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// This entry was deleted so we'll need to process it again.
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i--;
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}
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}
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return 0;
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}
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