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32 .\" @(#)getenv.3 8.2 (Berkeley) 12/11/93
44 .Nd environment variable functions
52 .Fn getenv "const char *name"
54 .Fn setenv "const char *name" "const char *value" "int overwrite"
56 .Fn putenv "char *string"
58 .Fn unsetenv "const char *name"
60 These functions set, unset and fetch environment variables from the
62 .Em environment list .
66 function clears all environment variables.
67 New variables can be added using
74 function obtains the current value of the environment variable,
76 The application should not modify the string pointed
83 function inserts or resets the environment variable
85 in the current environment list.
88 does not exist in the list,
89 it is inserted with the given
91 If the variable does exist, the argument
96 variable is not reset, otherwise it is reset
102 function takes an argument of the form ``name=value'' and
103 puts it directly into the current environment,
104 so altering the argument shall change the environment.
107 does not exist in the list,
108 it is inserted with the given
112 does exist, it is reset to the given
118 deletes all instances of the variable name pointed to by
122 If corruption (e.g., a name without a value) is detected while making a copy of
123 environ for internal usage, then
128 will output a warning to stderr about the issue, drop the corrupt entry and
129 complete the task without error.
133 function returns the value of the environment variable as a
138 is not in the current environment,
142 .Rv -std clearenv setenv putenv unsetenv
155 pointer, points to an empty string, or points to a string containing an
171 is the first character in
173 This does not follow the
182 failed because they were unable to allocate memory for the environment.
199 functions conforms to
218 and insert it into the environment using
220 This was changed to use
222 as the memory location of the ``name=value'' pair to follow the
233 that assign a larger-sized
235 than any previous value to the same
237 will result in a memory leak.
240 semantics for this function
241 (namely, that the contents of
243 are copied and that old values remain accessible indefinitely) make this
245 Future versions may eliminate one or both of these
246 semantic guarantees in order to fix the bug.