Envz vectors are just argz vectors with additional constraints on the form
of each element; as such, argz functions can also be used on them, where it
Each element in an envz vector is a name-value pair, separated by a '='
character; if multiple '=' characters are present in an element, those
after the first are considered part of the value, and treated like all other
If no'=' characters are present in an element, that element is
considered the name of a “null” entry, as distinct from an entry with an
empty value: envz_get will return 0 if given the name of null
entry, whereas an entry with an empty value would result in a value of
""; envz_entry will still find such entries, however. Null
entries can be removed with envz_strip function.
As with argz functions, envz functions that may allocate memory (and thus
fail) have a return type of error_t, and return either 0 or
These functions are declared in the standard include file envz.h.
The envz_entry function finds the entry in envz with the name
name, and returns a pointer to the whole entry—that is, the argz
element which begins with name followed by a '=' character. If
there is no entry with that name, 0 is returned.
The envz_get function finds the entry in envz with the name
name (like envz_entry), and returns a pointer to the value
portion of that entry (following the '='). If there is no entry with
that name (or only a null entry), 0 is returned.
The envz_add function adds an entry to *envz
(updating *envz and *envz_len) with the name
name, and value value. If an entry with the same name
already exists in envz, it is removed first. If value is
0, then the new entry will the special null type of entry
The envz_merge function adds each entry in envz2 to envz,
as if with envz_add, updating *envz and
*envz_len. If override is true, then values in envz2
will supersede those with the same name in envz, otherwise not.
Null entries are treated just like other entries in this respect, so a null
entry in envz can prevent an entry of the same name in envz2 from
being added to envz, if override is false.