Shell Programming and Scripting

# Example 1:
/usr/local/user_dir/bin/my_script -w 10 -c 50

# Example 2: *notice the trailing "/" after "my_script"...
/usr/local/user_dir/bin/my_script/ -w 10 -c 50

user_cmd="$1"

### The 1st Pattern here seems to match only the END of the Command (i.e. It Matches --> "/my_script -w 10 -c 50"
#COMMAND_PATTERN="((/){1,1}([[:alnum:]-_])+) .*"

COMMAND_PATTERN="((/[[:alnum:]_-]*)+).*$"

if [[ "$user_cmd" =~ $COMMAND_PATTERN ]]
 then
    echo "Command is Good"
else
    echo "Error: Command is Wrong"
fi

PATTERN="[/]([/]+| .*$)"

command[check_cmdAlias]=/path/to/the/command --option1 --option2 'etc, etc'

 # The User's Input is saved in "$new_command"

COMMAND_PATTERN="^(command)(\[{1,1}[[:alnum:]_-\ ]*\]{1,1})(={1,1})((/[[:alnum:]_-]*)+) .*$"

 # Check the User's new Command...
if [[ "$new_command" =~ $COMMAND_PATTERN ]]
  then
        COMMAND_PATTERN_MATCH=0
else
        COMMAND_PATTERN_MATCH=1
fi

 ### Check if the $new_command matched correctly
if [ $COMMAND_PATTERN_MATCH == 0 ]
 then
   # IF THE PATTERN IS CORRECT DO STUFF WITH IT HERE...
         ....MORE CODE....
else
   ### Call Function "bad_commandFormat()":
    #   This function will locate the problem in the New Check Command's Definition
    bad_commandFormat
fi

bad_commandFormat()
{
    ### Here I break up the COMMAND_PATTERN into 4 separate groups, incrementally adding the next group to the previous as it goes
    START_PATTERN="^(command)"
    ALIAS_PATTERN="^(command)(\[{1,1}[[:alnum:]_-\ ]*\]{1,1})"
    EQUALS_PATTERN="^(command)(\[{1,1}[[:alnum:]_-\ ]*\]{1,1})(={1,1})"
    PATH_PATTERN="^(command)(\[{1,1}[[:alnum:]_-\ ]*\]{1,1})(={1,1})((/[[:alnum:]_-]*)+) .*$"


      ### START Pattern: Begins with "command"
    if [[ ! "$new_command" =~ $START_PATTERN  ]]
     then
        format_ErrString="Your NEW Check_Command does NOT begin with the ${BOLD}\"command\"${OFF} keyword (*must be in ALL lower-case).\n"
        FORMAT_ERR="#1"

      ### ALIAS Pattern: String in-between "[...]" and after "command"
    elif [[ ! "$new_command" =~ $ALIAS_PATTERN  ]]
     then
        FORMAT_ERR="#2"
        format_ErrString="Your NEW Check_Command's ${BOLD}\"Alias\"${OFF} is not formatted correctly.\n"

      ### EQUAL Pattern: Check for equal sign after the alias pattern "command[...]="
    elif [[ ! "$new_command" =~ $EQUALS_PATTERN  ]]
     then
        FORMAT_ERR="#3"
        format_ErrString="A single ${BOLD}Equals Sign → \"=\"${OFF} should immediately follow your Check_Command's Alias.\n"

      ### PATH Pattern: Check for a path to a script after the "="
    elif [[ ! "$new_command" =~ $PATH_PATTERN  ]]
     then
        FORMAT_ERR="#4 and #5"
        format_ErrString="Your NEW Check_Command is missing an ${BOLD}Absolute Path${OFF} to the location of the NEW Check Command.\n"

      ### UNKNOWN: There was an error but we're not sure what the problem is...
    else
        format_ErrString="Found an Unknown Error for your NEW Check_Command. Please compare your command\n                with the example below and try again.\n"
        echo -ne "\tcommand[check_myAlias]=/usr/local/nagios/libexec/check_users -w 10 -c 15"
    fi
}

command[check_unixUsers]=/usr/local/nagios/libexec/check_users -w 10 -c 20

COMMAND_PATTERN="^(command)(\[{1,1})([[:alnum:]_\ -]*)(\]{1,1})(={1,1})((/[[:alnum:]_\-]+))+\ .*$"

## This Pattern will match any letter "A-z" any number "0-9", a "-", and a "_", all starting with a "/".
# Example Matching Pattern -->   "/usr" 
#   Using the Grouping method below combined with the "+" will say match one or more groups like these below:
#        "/usr"   "/my_dir"    "/my-dir"    "/dir_num1"    etc....
# *So if it finds a group like this --> "/usr/myCommand/ -w..."   it will fail!

 ((/[[:alnum:]_\-]+))+\ .*$