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32 .\" @(#)getenv.3 8.2 (Berkeley) 12/11/93
43 .Nd environment variable functions
49 .Fn getenv "const char *name"
51 .Fn setenv "const char *name" "const char *value" "int overwrite"
53 .Fn putenv "char *string"
55 .Fn unsetenv "const char *name"
57 These functions set, unset and fetch environment variables from the
59 .Em environment list .
63 function obtains the current value of the environment variable,
65 The application should not modify the string pointed
72 function inserts or resets the environment variable
74 in the current environment list.
77 does not exist in the list,
78 it is inserted with the given
80 If the variable does exist, the argument
85 variable is not reset, otherwise it is reset
91 function takes an argument of the form ``name=value'' and
92 puts it directly into the current environment,
93 so altering the argument shall change the environment.
96 does not exist in the list,
97 it is inserted with the given
101 does exist, it is reset to the given
107 deletes all instances of the variable name pointed to by
113 function returns the value of the environment variable as a
118 is not in the current environment,
122 .Rv -std setenv putenv unsetenv
135 pointer, points to an empty string, or points to a string containing an
146 .Fa string is without an
150 is the first character in
152 This does not follow the
161 failed because they were unable to allocate memory for the environment.
168 failed to make a valid copy of the environment due to the environment being
169 corrupt (i.e., a name without a value). A warning will be output to stderr with
170 information about the issue.
187 functions conforms to
206 and insert it into the environment using
208 This was changed to use
210 as the memory location of the ``name=value'' pair to follow the
216 that assign a larger-sized
218 than any previous value to the same
220 will result in a memory leak.
223 semantics for this function
224 (namely, that the contents of
226 are copied and that old values remain accessible indefinitely) make this
228 Future versions may eliminate one or both of these
229 semantic guarantees in order to fix the bug.