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32 .\" @(#)getenv.3 8.2 (Berkeley) 12/11/93
33 .\" $FreeBSD: src/lib/libc/stdlib/getenv.3,v 1.27 2007/07/04 00:00:39 scf Exp $
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44 .Nd environment variable functions
50 .Fn getenv "const char *name"
52 .Fn setenv "const char *name" "const char *value" "int overwrite"
54 .Fn putenv "char *string"
56 .Fn unsetenv "const char *name"
58 These functions set, unset and fetch environment variables from the
60 .Em environment list .
64 function obtains the current value of the environment variable,
66 The application should not modify the string pointed
73 function inserts or resets the environment variable
75 in the current environment list.
78 does not exist in the list,
79 it is inserted with the given
81 If the variable does exist, the argument
86 variable is not reset, otherwise it is reset
92 function takes an argument of the form ``name=value'' and
93 puts it directly into the current environment,
94 so altering the argument shall change the environment.
97 does not exist in the list,
98 it is inserted with the given
102 does exist, it is reset to the given
108 deletes all instances of the variable name pointed to by
114 function returns the value of the environment variable as a
119 is not in the current environment,
123 .Rv -std setenv putenv unsetenv
136 pointer, points to an empty string, or points to a string containing an
147 .Fa string is without an
151 is the first character in
153 This does not follow the
162 failed because they were unable to allocate memory for the environment.
169 failed to make a valid copy of the environment due to the environment being
170 corrupt (i.e., a name without a value). A warning will be output to stderr with
171 information about the issue.
188 functions conforms to
207 and insert it into the environment using
209 This was changed to use
211 as the memory location of the ``name=value'' pair to follow the
217 that assign a larger-sized
219 than any previous value to the same
221 will result in a memory leak.
224 semantics for this function
225 (namely, that the contents of
227 are copied and that old values remain accessible indefinitely) make this
229 Future versions may eliminate one or both of these
230 semantic guarantees in order to fix the bug.