What is the function of "VAR" in "foreach (VAR = [VAR1, VAR2, ...] in ARRAY) STMT"?

[Nan Xiao]

Hi all,

>From the "foreach" section in SystemTap
doc(https://sourceware.org/systemtap/langref/Statement_types.html#SECTION00076000000000000000),
I can see there is a foreach usage:

        foreach (VAR = [VAR1, VAR2, ...] in ARRAY) STMT

But execute the following script generate errors:

# cat test.stp
#!/usr/bin/stap

global reads

probe vfs.read
{
        reads[pid(), execname()]++
}

probe timer.s(3)
{
        foreach (var = [pid, name] in reads)
                printf("%d\n", reads[var]);
        exit()
}

# ./test.stp
semantic error: inconsistent arity (2 vs 1): identifier 'reads' at
./test.stp:13:18
        source:                 printf("%d\n", reads[var]);
                                               ^

semantic error: arity 2 first inferred here: identifier 'reads' at :7:2
        source:         reads[pid(), execname()]++
                        ^

Pass 2: analysis failed.  [man error::pass2]


What is the function of "VAR" in "foreach (VAR = [VAR1, VAR2, ...] in
ARRAY) STMT"? How to use it?
Thanks in advance!

Best Regards
Nan Xiao