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When doing string processing, it is often useful to be able to join
all the strings in an array into one long string. The following function,
join()
, accomplishes this task. It is used later in several of
the application programs
(see section Practical awk
Programs).
Good function design is important; this function needs to be general, but it
should also have a reasonable default behavior. It is called with an array
as well as the beginning and ending indices of the elements in the array to be
merged. This assumes that the array indices are numeric—a reasonable
assumption, as the array was likely created with split()
(see section String-Manipulation Functions):
# join.awk --- join an array into a string function join(array, start, end, sep, result, i) { if (sep == "") sep = " " else if (sep == SUBSEP) # magic value sep = "" result = array[start] for (i = start + 1; i <= end; i++) result = result sep array[i] return result }
An optional additional argument is the separator to use when joining the
strings back together. If the caller supplies a nonempty value,
join()
uses it; if it is not supplied, it has a null
value. In this case, join()
uses a single space as a default
separator for the strings. If the value is equal to SUBSEP
,
then join()
joins the strings with no separator between them.
SUBSEP
serves as a “magic” value to indicate that there should
be no separation between the component strings.71
It would
be nice if awk
had an assignment operator for concatenation.
The lack of an explicit operator for concatenation makes string operations
more difficult than they really need to be.
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