POSIX print function definition

Question

Bash can print a function defintion:

$ bash -c 'y(){ echo z; }; export -f y; export -f'
y ()
{
    echo z
}
declare -fx y

However this fails under POSIX Bash, /bin/sh and /bin/dash:

$ bash --posix -c 'y(){ echo z; }; export -f y; export -f'
export -f y

Can a function definition be printed under a POSIX shell?

Answer 1

You can not do it portably. POSIX spec did not specify any way to dump function definition, nor how functions are implemented.

---

In bash, you don't have to export the function to the environment, you can use:

declare -f funcname

(Work in zsh)

This works even you run bash in posix mode:

$ bash --posix -c 'y(){ echo z; }; declare -f y'
y () 
{ 
    echo z
}

---

In ksh:

typeset -f funcname

(Works in bash, zsh, mksh, pdksh, lksh)

---

In yash:

typeset -fp funcname

This won't work if yash enter POSIXly-correct mode:

$ yash -o posixly-correct -c 'y() { ehco z; }; typeset -fp y'
yash: no such command `typeset'

---

With zsh:

print -rl -- $functions[funcname]
whence -f funcname
type -f funcname
which funcname

Note that both whence -f, which, type -f will report alias first with the same name. You can use -a to make zsh report all definitions.

---

POSIXly, you'd have to record your function definition yourself which you could do with:

myfunction_code='myfunction() { echo Hello World; }'
eval "$myfunction_code"

or a helper function

defn() {
  code=$(cat)
  eval "${1}_code=\$code; $1() { $code; }"
}

defn myfunction << 'EOF'
echo Hello World
EOF

printf '%s\n' "$myfunction_code"

Answer 2

No. At least, not to my knowledge.

-f is an extension to POSIX export.

POSIX set (and bash set in POSIX mode) also excludes function definitions.