Setting Shell Positional Parameters With "set ls -AF" - shell

Question

I am writing a ksh function (that is placed in the .profile file) that will present a menu of subdirectories and permit the user to choose one into which to cd. Here is the code:
# Menu driven subdirectory descent.
d(){
# Only one command line argument accepted
[ "$1" = "--" ] && shift $# # Trap for "ls --" feature
wd=`pwd`; arg="${1:-$wd}"
dirs="`/bin/ls -AF $arg 2>/dev/null | grep /$ | tr -d \"/\"`"
# Set the names of the subdirectories to positional parameters
if [ "$dirs" ] ;then
set $dirs
if [ $# -eq 1 -a "$arg" = "$wd" ] ;then cd $arg/$1; return; fi # trap: it's obvious; do it
else echo "No subdirectories found" >&2; return 1
fi
# Format and display the menu
if [ `basename "${arg}X"` = "${arg}X" ] ;then arg="$wd/$arg"; fi # Force absolute path if relitive
echo -e "\n\t\tSubdirectories relative to ${arg}: \n"
j=1; for i; do echo -e "$j\t$i"; j=`expr $j + 1`; done | pr -r -t -4 -e3
echo -e "\n\t\tEnter the number of your choice -- \c "
# Convert user-input to directory-name and cd to it
read choice; echo
dir=`eval "(echo $\{"$choice"\})"` # Magic here.
[ "$choice" -a "$choice" -ge 1 -a "$choice" -le "$#" ] && cd $arg/`eval echo "$dir"`
}
This function works reasonably well with the exception of directory names that contain space characters. If the directory name contains a space, the set command sets each space delimited element of the directory name (instead of the complete directory name) into a separate positional parameter; that is not useful here.
I have attempted to set the $IFS shell variable (which contains a space, tab, and newline by default) to a single newline character with:
IFS=`echo` # echo outputs a trailing newline character by default
Which appears to accomplish what is intended as verified with:
echo -e "$IFS\c" | hexdump -c
But despite my best efforts (over the course of several days work) I have failed to set the entire directory names that contain spaces as values for positional parameters.
What am I missing?
Suggestions are hereby solicited and most welcome.
ADVAthanksNCE
Bob

Answer 1

Short answer: You can't do that. Don't try. See the ParsingLs page for an understanding of why programmatic use of ls is inherently error-prone.
You can't get -F behavior without implementing it yourself in shell (which is indeed feasible), but the following is the correct way to put a list of subdirectories into the argument list:
set -- */
If you don't want to have a literal / on the end of each entry:
set -- */ # put list of subdirectories into "$#"
set -- "${#%/}" # strip trailing / off each
Even better, though: Use an array to avoid needing eval magic later.
dirs=( */ )
dirs=( "${dirs[#]%/}" )
printf '%s\n' "${dirs[$choice]}" # emit entry at position $choice
Let's tie this all together:
d() {
destdir=$(
FIGNORE= # ksh93 equivalent to bash shopt -s dotglob
while :; do
subdirs=( ~(N)*/ ) # ksh93 equivalent to subdirs=( */ ) with shopt -s nullglob
(( ${#subdirs[#]} > 2 )) || break # . and .. are two entries
for idx in "${!subdirs[#]}"; do
printf '%d) %q\n' "$idx" "${subdirs[$idx]%/}" >&2
done
printf '\nSelect a subdirectory: ' >&2
read -r choice
if [[ $choice ]]; then
cd -- "${subdirs[$choice]}" || break
else
break
fi
done
printf '%s\n' "$PWD"
)
[[ $destdir ]] && cd -- "$destdir"
}

Answer 2

Although still not working, this version does pass shellcheck albeit with one exception:
3 # Menu driven subdirectory descent.
4 function d{
5 # Only one command line argument accepted
6 [ "$1" = "--" ] && shift $# # Trap for "ls --" feature
7 wd="$PWD"; arg="${1:-$wd}"
8 set -- "${#%/}" # Set the names of the subdirectories to positional parameters
9 if [ $# -eq 1 -a "$arg" = "$wd" ] ;then cd "$arg/$1" || exit 1; return; # trap: it's obvious; do it
10 else echo "No subdirectories found" >&2; return 1
11 fi
12 # Format and display the menu
13 if [[ $(basename "${arg}X") = "${arg}X" ]] ;then arg="$wd/${arg}"; fi # Force absolute path if relitive
14 echo -e "\n\t\tSubdirectories relative to ${arg}: \n"
15 j=1; for i; do echo -e "$j\t$i"; j=(expr $j + 1); done | pr -r -t -4 -e3
16 echo -e "\n\t\tEnter the number of your choice -- \c "
17 # Convert user-input to directory-name and cd to it
18 read -r choice; echo
19 dir=(eval "(echo $\{\"$choice\"\})") # Magic here.
20 [ "$choice" -a "$choice" -ge 1 -a "$choice" -le "$#" ] && cd "${arg}"/"$(eval echo "${dir}")" || exit 1
^SC2128 Expanding an array without an index only gives the first element.
21 }
Once I have incorporated your suggestions into the code, and made it functional, I'll post it here, and mark my question answered. Thank you for your kind assistance.

Answer 3

I've used the code you kindly wrote as a basis for the d function below. It pretty much does what I'd like, with a few little issues:
All subdirectory names that contain a SPACE character are surrounded by characters, but those that do not are not.
All subdirectory names that contain a SINGLE QUOTE character have that character escaped with a BACKSLASH character.
Given that 1 and 2 above cause no issues, they are acceptable, but not ideal.
After user input does the cd, the menu of subdirectory names is again looped through. This could be considered a feature, I suppose. I tried substituting a return for the brake commands in the sections of code following the cd commands, but was unsuccessful in overcoming the subsequent looped menu.
The inclusion of "." and ".." at the head of the menu of subdirectories is not ideal, and actually serves no good purpose.
------------------- Code Begins ------------------------------
d() {
if [ "$BASH" ] && [ "$BASH" != "/bin/sh" ]; then
echo "$FUNCNAME: ksh only";return 1
fi
FIGNORE= # ksh93 equivalent to bash shopt -s dotglob
if [ ${#} -gt 0 ] ;then # Only one command line argument accepted
cd -- "$1" && return 0
fi
if [ `ls -AF1|grep /|wc -l` -eq 1 ] ;then # cd if only one subdirectory
cd -- `ls -AF1|grep /` && return 0
fi
destdir=$(
while :; do
subdirs=( ~(N)*/ ) # ksh93 equivalent to subdirs=( */ ) with shopt -s nullglob
(( ${#subdirs[#]} > 2 )) || break # . and .. are two entries
echo -e "\n\t\tSubdirectories below ${PWD}: \n" >&2
for idx in "${!subdirs[#]}"; do
printf '%d) %q\n' "$idx" "${subdirs[$idx]%/}" >&2
done
printf '\nSelect a subdirectory: ' >&2
read -r
if [[ $REPLY ]]; then
cd -- "${subdirs[$REPLY]}" || break # Continue to loop through subdirectories after cding
else
break
fi
done
printf '%s\n' "$PWD"
)
--------------------------- Code Ends ------------------------------------
So, overall I'm very pleased, and consider myself very fortunate to have received the knowledgeable assistance of such an accomplished Unix wizard. I can't thank you enough.