Infinite loop when trying to launch a symbolic-link to a bash script

Question

I am trying to create a symbolic-link by using:

$ ln -s path/to/foo.sh ~/.local/bin/bar

In the path where foo.sh is executed there is another file, named foo.

The following bash-script executes successfully when launched directly from the terminal (i.e. $ ./foo.sh), however, when I use the symbolic-link bar, it throws an error:

# foo.sh

  1 #!/usr/bin/env bash
  2  appname=`basename $0 | sed s,\.sh$,,`
  3 
  4  dirname=`dirname $0`
  5  tmp="${dirname#?}"
  6 
  7  if [ "${dirname%$tmp}" != "/" ]; then
  8  dirname=$PWD/$dirname
  9  fi
 10  LD_LIBRARY_PATH=$dirname
 11  export LD_LIBRARY_PATH
 12  $dirname/$appname $*

I don't understand why i get the following error, when I try to launch, script above from the symbolic link bar:

bash: warning: shell level (1000) too high, resetting to 1

Answer 1

Resolve symlink before processing the file.

foo.sh

#!/bin/bash

# Mark variable for export.
declare -xi LVL

# Resolve absolute pathname.
filename=$(realpath "$0")

# Strip .sh suffix from file and check for exec bit.
((LVL++ < 1)) && [[ -x "${filename%.sh}" ]] || exit 1

export LD_LIBRARY_PATH="${filename%/*}"

# Run it!
"${filename%.sh}" "$@"

foo

#!/bin/bash
echo "$@"

Now we can create a symlink:

$ ln -s /path/to/foo.sh bar

^{Regardless of the symlink's name, it is the file foo that will be executed.}