portable unix way to join strings with separator

Question

Is there a portable unix shellscripting way of joining a number of strings together with a given separator, like so:

$ strjoin --- foo bar baz quux
foo---bar---baz---quux

Sure I could use a $scripting_language one liner or an ugly explicit loop in a shellscript function, but the unix hackers of old probably had some need for this as well, so someone has made a standard command like this that I don't know about somewhere in the past, right?

Answer 1

In addition to @embobo's comment (which will hopefully make it into an answer soon), perl can be used to split and join arbitrary strings. This is more complex than using sed and based on the example above would be major overkill.

Answer 2

awk version:

function join(a, start, end, sep, result, i) {
    sep = sep ? sep : " "
    start = start ? start : 1
    end = end ? end : sizeof(a)
    if (sep == SUBSEP) # magic value
       sep = ""
    result = a[start]
    for (i = start + 1; i <= end; i++)
        result = result sep a[i]
    return result
}

Call it with gawk with --source is your strings:

$ gawk -f join.awk --source 'BEGIN { split("foo bar quux",a); print join(a,1,3,"---") }'
foo---bar---quux

---

Shell script version:

function join() {
    for i in "$@"; do
        echo -n "$i""---"
    done
    echo
}

join foo bar baz quux 

Call it and trim the last separator:

$ ./join.sh | sed 's/\-\-\-$//'
foo---bar---baz---quux

Answer 3

Perl is not that complex for simple operations:

$ perl -e 's/ /---/g'