Function scoped variable should retain its last value in while-loop body

[earlchew]

Description of problem:
When a function scoped variable is set in the body of a while loop, the variable appears to lose the value when the loop is restarted.

Ksh version:

# print -v .sh.version
Version AJM 93u+ 2012-08-01

How reproducible:
Easily reproduced from console. The output from dash, and bash, is less surprising:

$ dash /tmp/foo.sh | head -4
/tmp/foo.sh: 11: print: not found
/tmp/foo.sh: 13: typeset: not found

+
+
+

Steps to reproduce:

$ cat /tmp/foo.sh
f()
{
    typeset X

    while : ; do
        echo "${X++}"
        X=1
    done
}

print -v .sh.version

f

$ ksh /tmp/bug.sh | head
Version AJM 93u+ 2012-08-01









```

[marcastel]

Using an alternate value in KornShell is not ${parameter+word} but {parameter:+word}.

The following should achieve what you are expecting (both in KornShell and Bash).

    while : ; do
        echo "${X:++}"
        X=1
    done | head

That is an empty line followed by 9 lines with 1 x -- assuming the default for head(1) on your platform is 10.

BTW. Please read also @jghub's comment in #1475 about this repo.

[earlchew]

@marcastel Thanks for the feedback, and I appreciate the suggested workaround.

[jelmd]

Well, your script works as expected: you set X=1 and echo the contents of another var named X++. Since you never set the value of this var, it is empty - you get, what you are asking for.
dash is obviously buggy wrt. the output of the script.