Each argz vector is represented by a pointer to the first element, of
type char *, and a size, of type size_t, both of which can
be initialized to 0 to represent an empty argz vector. All argz
functions accept either a pointer and a size argument, or pointers to
them, if they will be modified.
The argz functions use malloc/realloc to allocate/grow
argz vectors, and so any argz vector creating using these functions may
be freed by using free; conversely, any argz function that may
grow a string expects that string to have been allocated using
malloc (those argz functions that only examine their arguments or
modify them in place will work on any sort of memory).
See Unconstrained Allocation.
All argz functions that do memory allocation have a return type of
error_t, and return 0 for success, and ENOMEM if an
allocation error occurs.
These functions are declared in the standard include file argz.h.
The argz_create function converts the Unix-style argument vector
argv (a vector of pointers to normal C strings, terminated by
(char *)0; see Program Arguments) into an argz vector with
the same elements, which is returned in argz and argz_len.
The argz_extract function converts the argz vector argz and
argz_len into a Unix-style argument vector stored in argv,
by putting pointers to every element in argz into successive
positions in argv, followed by a terminator of 0.
Argv must be pre-allocated with enough space to hold all the
elements in argz plus the terminating (char *)0
((argz_count (argz, argz_len) + 1) * sizeof (char *)
bytes should be enough). Note that the string pointers stored into
argv point into argz—they are not copies—and so
argz must be copied if it will be changed while argv is
still active. This function is useful for passing the elements in
argz to an exec function (see Executing a File).
— Function: void argz_stringify (char *argz, size_t len, int sep)
The argz_stringify converts argz into a normal string with
the elements separated by the character sep, by replacing each
'\0' inside argz (except the last one, which terminates the
string) with sep. This is handy for printing argz in a
The argz_add_sep function is similar to argz_add, but
str is split into separate elements in the result at occurrences of
the character delim. This is useful, for instance, for
adding the components of a Unix search path to an argz vector, by using
a value of ':' for delim.
If entry points to the beginning of one of the elements in the
argz vector *argz, the argz_delete function will
remove this entry and reallocate *argz, modifying
*argz and *argz_len accordingly. Note that as
destructive argz functions usually reallocate their argz argument,
pointers into argz vectors such as entry will then become invalid.
The argz_insert function inserts the string entry into the
argz vector *argz at a point just before the existing
element pointed to by before, reallocating *argz and
updating *argz and *argz_len. If before
is 0, entry is added to the end instead (as if by
argz_add). Since the first element is in fact the same as
*argz, passing in *argz as the value of
before will result in entry being inserted at the beginning.
The argz_next function provides a convenient way of iterating
over the elements in the argz vector argz. It returns a pointer
to the next element in argz after the element entry, or
0 if there are no elements following entry. If entry
is 0, the first element of argz is returned.
Note that the latter depends on argz having a value of 0 if
it is empty (rather than a pointer to an empty block of memory); this
invariant is maintained for argz vectors created by the functions here.