POSIX shell function to "dump" all given arguments

Question

My today's idea was to create a POSIX shell function to dump all given arguments, typical use would be to call it from a fucntion, where you already know some arguments are not well set (empty; not integer) and this way you can inspect all given arguments in one go. It reminds me of a PHP var_dump function. :) Would anyone be able to find weak spots in there, all input is welcome.

---

#!/bin/sh
dump_arguments ()
# string function - prints arguments (position and content)
# indicates empty arguments and integer numbers
{
 printf '%b' "dump_arguments()\\n----------------\\n$# arguments are being inspected"
 [ $# -gt 0 ] && { printf ':\n'; i=1; } || printf '.\n'
 while [ $# -gt 0 ]; do
 printf '%s' "[$i]: '1ドル'"
 [ -z "1ドル" ] && printf ' (empty)'
 [ "1ドル" -eq "1ドル" ] 2> /dev/null && printf ' (integer)'
 printf '\n'
 shift 1
 i=$((i+1))
 done
} >&2
# inside some function you would call it like this
dump_arguments "$@"
# but to only try it out, you can call it directly
dump_arguments '1' '' 5

• Gao: I forgot the specifics, but you might want to check the behavior of your script, specifically the line starting with [ "1ドル" -eq "1ドル" ], in yash and zsh, since how they handle the algebraic checks is a bit different from your regular shells like bash.
• Gao: OK I dug through my notes and can be more specific about how yash and zsh behave differently with respect to the algebraic checks. They are a bit more strict, in that if there are trailing spaces, the word would not be considered an integer. But in bash and most other shells, [ "1 " -eq "1 " ] would return with exit status 0 without any warning or error messages.
• Vlastimil Burián: @Gao I don't use this check anymore. See unix.stackexchange.com/a/598047/126755 for more proper check which I use now. Cheers, and thanks for the comment

Answer 1

printf '%b' "dump_arguments()\\n----------------\\n$# arguments are being inspected"

We could make that easier to read by making each line a separate argument, and ending the line properly (rather than requiring a separate command):

punct=.
${1+false} true || punct=:
printf '%s\n' \
 'dump_arguments()' \
 '----------------' \
 "$# arguments are being inspected$punct"

It seems odd to use %s here:

 printf '%s' "[$i]: '1ドル'"

Why not use the format string more clearly? And this allows us to modify to use %q if we have a suitable printf:

 printf "[%d]: '%s'" "$i" "1ドル"

Perhaps even combine the type into a single print:

 type=
 [ -z "1ドル" ] && type=' (empty)'
 [ "1ドル" -eq "1ドル" ] 2>/dev/null && type=' (integer)'
 printf "[%d]: '%s'%s\n" "$i" "1ドル" "$type"

Is it intentional that strings such as ' 5' (with leading and/or trailing spaces) are counted as integers?

 shift 1

Normally written simply as

 shift

That said, I think it's more natural to iterate over arguments using a for loop instead.

} >&2

That's surprising, as the output isn't an error, but expected when calling the function. It should be up to the caller to choose where stream 1 goes.

---

Modified code

#!/bin/sh
dump_arguments()
# string function - prints arguments (position and content)
# indicates empty arguments and integer numbers
{
 punct=${1+:}
 printf '%s\n' \
 'dump_arguments()' \
 '----------------' \
 "$# arguments are being inspected${punct:-.}"
 i=1
 for v
 do
 if [ -z "$v" ]
 then type=' (empty)'
 elif [ "$v" -eq "$v" ] 2>/dev/null
 then type=' (integer)'
 else type=
 fi
 printf "[%d]: '%s'%s\n" \
 "$i" "$v" "$type"
 i=$((i+1))
 done
}

• Toby Speight: No, I just didn't show that line. There's no harm in defining it regardless, so I just wrote it before the loop. I'll edit to show my full modified version.