[ -x /pathto/file ]

#!/bin/bash
#
# @(#)$Id: permission,v 1.3 2012/06/15 03:20:13 rwilliams final root $
# @(#)$Purpose: Determine if <user> has <permission> on <file|directory>$
# @(#)$Comment: this script is intended to be sourced, from a parent shell$
# @(#)$Usage: permission <user> <permission> <file|directory>$
# @(#)$Return: 0 TRUE, 1 FALSE, 99 NOT PROCESSED$
#

# Automatically export defined functions
set -a

permission() {
  { [ -n "$1" ] && [ -n "$2" ] && [ -n "$3" ]; } || return 99;
  chk="{ [ -${2} ${3} ] && exit 0; } || exit 1;"
  sudo -u ${1} bash -c "${chk}"
  return $?
}

# Skip testing if no command-line parameters were given
{ [ -n "$1" ] && [ -n "$2" ] && [ -n "$3" ]; } \
&& permission $1 $2 $3 && exit $?

#!/bin/bash
# 
# @(#)$Id: permission,v 1.4 2012/06/15 22:07:35 rilliams final root $
# @(#)$Purpose: Determine if <user> has <permission> on <file|directory>$
# @(#)$Comment: this script is intended to be sourced, from a parent shell$
# @(#)$Usage: permission <user> <permission> <file|directory>$
# @(#)$Return: 0 TRUE, 1 FALSE, 99 NOT PROCESSED$
#
set -a
permission() { 
  [ ${#@} -eq 3 ] || return 99; 
  runuser $1 -c "[ -$2 $3 ] || exit 1;"; }
permission $1 $2 $3 && exit $?;

sudo -u "$USER" -- test -r "$FILE" && echo "$USER can read $FILE"
sudo -u "$USER" -- test -w "$FILE" && echo "$USER can write to $FILE"
sudo -u "$USER" -- test -x "$FILE" && echo "$USER can execute $FILE"
sudo -u "$USER" -- cd "$DIR" &>/dev/null && echo "$USER can enter $DIR"

#!/bin/bash
[ "$(id -u)" = "0" ] || exec sudo -n -- "$0" "$@"

User="$1"
shift 1

if ! id -u "$User" &>/dev/null ; then
    printf '%s: No such user.\n' "$User" >&2
    exit 1
fi

exec sudo -n -u "$User" -- /usr/bin/test "$@"

test-user "$user" -d "$dir" -a -w "$dir" && echo "$user can create files in directory $dir"
test-user "$user" -w "$file" && echo "$user can write to $file"

~$ USER=root
~$ DIR=/
~$ sudo -u "$USER" -- cd "$DIR" &>/dev/null && echo "$USER can enter $DIR" || echo "$USER can't enter $DIR"
root can't enter /
~$ sudo -u "$USER" -- cd "$DIR" 
sudo: cd: command not found

sudo -n -u "$USER" -- bash -c "cd '$DIRSQ'" &>/dev/null

SQ="'"
ESQ="'\"'\"'"
[ -n "$DIR" ] || exit 1
sudo -n -u "$USER" -- bash -c "cd '${DIR//$SQ/$ESQ}'" &>/dev/null || exit 1

sudo -n -u "$USER" -- bash -c 'cd "$0"' "$DIR" &>/dev/null

#!/bin/bash

# Make sure we have root privileges.
[ "$(id -u)" != "0" ] || exec sudo -n -- "$0" "$@"

# Usage requested?
if [ $# -lt 1 ] || [ "$1" = "-h" ] || [ "$1" = "--help" ]; then
    exec >&2
    echo "Usage: $0 [ -h | --help ]"
    echo "       $0 USER -drw DIR(s)..."
    echo "       $0 USER -frwx FILE(s)..."
    echo "Where:"
    echo "       -d DIR    USER can enter DIR"
    echo "       -w ITEM   USER can write to ITEM"
    echo "       -r ITEM   USER can read ITEM"
    echo "       -f FILE   FILE is a regular file"
    echo "       -x FILE   USER can execute FILE"
    echo ""
    echo "If all tests are successful, this will return success (exit status 0)."
    echo "If any of the tests fail, this will return failure (exit status 1)."
    echo "If USER is not valid user, this will return failure (exit status 2)."
    echo "In case of other errors, this will return failure (exit status 3)."
    echo ""
    exit 3
fi

# Use POSIX/C locale to avoid problems with non-UTF-8 file names in UTF-8 locales.
export LANG=C
export LC_ALL=C

User="$1"
shift 1

# Courtesy user check
if ! id -u "$User" &>/dev/null ; then
    echo "$User: No such user." >&2
    exit 2
fi

while [ $# -gt 0 ]; do
    Opts="${1#-}"
    if [ "$Opts" = "$1" ]; then
        echo "$1: Unsupported test." >&2
        exit 3
    fi
    shift 1

    if [ -z "$1" ]; then
        echo "No files or directories specified for $Opts." >&2
        exit 3
    fi

    case "$Opts" in
      d) sudo -n -u "$User" -- bash -c 'cd "$0"' "$1" &>/dev/null || exit 1
         shift 1
         ;;
      f) sudo -n -u "$User" -- test -f "$1" &>/dev/null || exit 1
         shift 1
         ;;
      r) sudo -n -u "$User" -- test -r "$1" &>/dev/null || exit 1
         shift 1
         ;;
      w) sudo -n -u "$User" -- test -w "$1" &>/dev/null || exit 1
         shift 1
         ;;
      x) sudo -n -u "$User" -- test -x "$1" &>/dev/null || exit 1
         shift 1
         ;;
      *) echo "-$Opts: Unsupported test." >&2
         exit 3
         ;;
    esac

    # Opts may contain more than one test. We handled the first one, so remove it.
    Opts="${Opts#?}"
done

# Success.
exit 0