$(echo "cd ..") Command not found

Question

Good ol' -bash: cd ..: command not found.

I have a script I wrote to traverse up to a named directory. It had been working and now for the life of me I don't know what's changed.

$ type up
up is a function
up () 
{ 
    local arg="$@";
    if [ -z "$arg" ]; then
        cd ..;
        return 1;
    fi;
    local arr=();
    local sep='/';
    local IFS="$sep";
    local DIRS;
    read -ra DIRS <<< "$(pwd)";
    for ((i=${#DIRS[@]}-1; i>=0; i-- ))
    do
        if [ "${DIRS[i]}" = "$arg" ]; then
            local first=${arr[0]};
            arr=("${arr[@]:1}");
            $(printf "%s" "cd $first" "${arr[@]/#/$sep}" && echo "/");
            return 1;
        else
            arr+=('..');
        fi;
    done;
    echo "Directory \"$arg\" could not be found in path. Check spelling and try again." 1>&2;
    return 0
}

Steps

1. if no arg is passed, go up a directory
2. if an arg is passed:

   1. grab the pwd and split on /

   2. iterate over the list of dirs walking from the back of the queue

   3. if the current dir doesn't match the arg, add .. to a list

   4. if the dir matches the command line arg, unpack .., delimit with /, and execute the string as a command

      printf "%s" "cd $first" "${arr[@]/#/$sep}" && echo "/"
      
      # printf "%s" "cd $first" :   prints 'cd ..' (command & the first placeholder) 
      # "${arr[@]/#/$sep}"      :   prints the remaining '..' joined by '/'
      # echo "/"                :   adds a trailing '/' to the relative path 
      #                               which could have been included in the 
      #                               previous step but separated for comprehension
      
      # Given, pwd = /Users/dev/workspace/project/foo
      # `up workspace` navigates to 'cd ../../'
      

Debugging (from the terminal)

> cd ..
# works as expected

> $(echo "cd ..")
# works as expected --> maybe something with the "/" is breaking it?

> $('cd ..')
# -bash: cd ..: command not found

> $('cd ../')
# -bash: cd ../: No such file or directory

> which cd
# /usr/bin/cd

> echo $PATH
# /usr/bin

> type cd
# cd is a shell builtin

> alias cd
# -bash: alias: cd: not found

> shopt expand_aliases
# expand_aliases    on

Unsetting most of the environment variables (e.g., CDPATH) or opening a shell with a clean environment (i.e. env -i bash --noprofile --norc) did not help in bash3.2 on OSX.

Comments

My bash is a little rusty, so feel free to give pointers on a better way, that's as maintainable. I know return may not be necessary (or correct) and I've seen some find implementations, which were probably more efficient, but more difficult to follow.

Answer 1

$(echo "cd ..") runs the shell command echo "cd .." (that is, the command echo with the single argument cd ..), takes the output (cd ..), splits that on whitespace (and globs, though that doesn't matter here), gets the two words cd and .., and runs the cd with the argument ... That's a convoluted and error-prone way of just running the shell command cd ...

Except that here, you've set IFS to a slash, so the word splitting part doesn't split on whitespace, but on slashes.

So, when you do e.g. $(echo "cd ../.."), the result of the command substitution is split not as cd, ../.., but as cd .., ... The space now being part of the command name here as if you entered "cd .." .. on the shell command line.

It's likely better not to rely on word-splitting to get it right (especially since it'll break the moment your directory names contain whitespace), but to keep the command and argument separate. Build the directory name in a variable and use that, i.e.:

dir=$(printf "../..")
cd -- "$dir" 

Or perhaps rather

printf -v dir "../.."
cd -- "$dir" 

---

Also, you might not need that printf there. You can use "${arr[*]}" to get the array elements joined with the first character of IFS, so with IFS=/, it would join them with slashes.

E.g.:

arr=(.. .. ..)
IFS=/
dir="${arr[*]}"

sets dir to ../../...