[SOLVED] bash script parameters and logic

asistant · 04-15-2012, 10:35 PM

Hello everyone,

I am trying to create a basic script with the following requirements:

When no command line arguments at all are present, the script will print a helpful "Usage" message listing the possible options and arguments, and exit. I think i got this one.
Example: sh myscript.sh

The script's default function when no options are given on the command line, but a <name> is supplied, is to print all lines in my address_book file.
Example: sh myscript.sh Bill

If the '-a' option is present, the script will prompt for the data items in the record (name,and email address), construct a data record with the appropriate format, and add it to the 'address_book' file.
Example: sh myscript.sh -a

If the '-b' option is present, the script will mail a personalized greeting to the email address of every person in 'address_book' whose day of birth is today.
Example: sh myscript.sh -b

I am new to bash scripting language and I am having trouble to construct script logic.

I create the first part it worked fine and I am trying to construct the rest part. Here is what i have so far.

Code:

[asistant@myserver]$ cat test5
#!/bin/bash

function help_menu {
    echo "Usage: $0 [-a] [-b ] [<name>]";
   echo "Options";
   echo "$0 [-a] Add record to address book";
   echo "$0 [-b] Send personalized greeting whose birthday is today";
   echo "$0 [<name>] search for specified name"
}

function search_name {
Name=$1
    grep $Name ~/address_book;
    echo " do something more"
}

if test $# -eq 0;
 then
    help_menu

elif [ "$Name"="-b" ];
 then
     search_name "$Name"          
    exit 0
fi

exit 0

can somebody help me with this or show me sample?

Any input greatly appreciated.

Thanks.

konsolebox · 04-15-2012, 11:03 PM

How do you add record to the address book and how do you send a personalized greeting? I mean the commands.

catkin · 04-15-2012, 11:59 PM

It would be simpler to separate command line parsing (and error trapping) from the actions. Assuming you would like to add a -h option to get verbose help, then something like this

Code:

    # Parse command line
    # ~~~~~~~~~~~~~~~~~~
    emsg=''
    nl=$'\n'    # newline
    name=
    opt_a=
    opt_b=
    while getopts abh opt 2>/dev/null
    do
        case $opt in
            a )
                opt_a=true
                ;;
            b )
                opt_b=true
                ;;
            h )
                usage -v
                exit 0
                ;;
            * )
                emsg="${nl}Invalid option '$opt'"
        esac
    done

    # Test for optional argument
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~
    shift $(( $OPTIND-1 ))
    if [[ $1 != '' ]]; then
       name=$1
       shift
    fi

    # Test for extra arguments
    # ~~~~~~~~~~~~~~~~~~~~~~~~
    if [[ $* != '' ]]; then
        emsg="${nl}Invalid extra argument(s) '$*'"
    fi

    # Report any errors
    # ~~~~~~~~~~~~~~~~~
    if [[ $emsg != '' ]]; then
        echo "$emsg" >&2
        usage
        exit 1
    fi

if [[ $opt_a != '' ]]; then
    <whatever> 
fi

if [[ $opt_b != '' ]]; then
    <whatever> 
fi

if [[ $name != '' ]]; then
    <whatever> 
fi

grail · 04-16-2012, 01:15 AM

May I also suggest for the usage / help function that you have a look at here documents. I find this particularly helpful, especially
if the size of the information will grow or vary.

Also, whilst getopts presented by catkin is fine, if you wish to play a bit more with bash you could produce your own simple parser to search for strings starting with a hyphen
and use a similar case to set the appropriate options:

Code:

for arg
do
    if [[ ${arg:0:1} == "-" ]]
    then
        <do case here>
    else
        OTHER+=( "$arg" )
    fi
done

Reuti · 04-16-2012, 06:33 AM

Quote:

Originally Posted by grail

Also, whilst getopts presented by catkin is fine, if you wish to play a bit more with bash you could produce your own simple parser to search for strings starting with a hyphen
and use a similar case to set the appropriate options:

While parsing by shell programming might be more portable across different shells, the getopts builtin in bash has the advantage to allow to concatenate options, i.e. -ab is the same like -a -b.

grail · 04-16-2012, 10:23 AM

Quote:

While parsing by shell programming might be more portable across different shells, the getopts builtin in bash has the advantage to allow to concatenate options, i.e. -ab is the same like -a -b.

And a little coaxing in a loop over the string after the hyphen can perform the same ... I just like to play

I would add that long options are also handled a little easier than with getopts.

Nominal Animal · 04-16-2012, 07:09 PM

Quote:

Originally Posted by Reuti

While parsing by shell programming might be more portable across different shells, the getopts builtin in bash has the advantage to allow to concatenate options, i.e. -ab is the same like -a -b.

Quote:

Originally Posted by grail

I would add that long options are also handled a little easier than with getopts.

As it happens, I wrote a skeleton script along those very lines recently myself.

It handles -a a-param -b the same as -ab a-param, and also supports long options with or without values, i.e --help, --type=value or --type value .

I'm sure sharp minds here could find ways to enhance it, though.

asistant · 04-17-2012, 10:07 AM

Than you very much everyone for the help and inputs.

Here what i have so far it looks like it is working fine at this point now I am trying to fill each functions to perform actual work.

Code:

#!/bin/bash

function display_help {
    echo "Usage: $0 [-a] [-b ] [<name>]";
	echo "OPTIONS:";
	echo "		[-a] Add record to address book";
	echo "		[-b] Send personalized greeting whose birthday is today";
	echo "		[<name>] search for specified name"
}

function search_name {
addressfile=~/myaddrbook

    grep "$1" $addressfile | tr ":" " "
	echo
    	echo "listed above"
}

function add_record {
    echo "Adding Record to database";
	echo "do more"
}

function send_b_greetings {
    echo "Sending birthday greetings";
	echo "Still working progress"
}


if [ $# -eq 0 ]; then
    display_help
    exit 1
fi    

if [ -n "$1" ]; then
	search_name
fi

# Now parse command line arguments

while getopts "ab" var;
do
    case "$var" in
	a) add_record;;
	b) send_b_greetings;;
	\?) display_help; exit 1;; 
    esac
done

Here is my address sample book format:
Elizabeth:Miller:A:55 W. Main Street:Camp Hill:CA:94500:717-502-0334:elizabeth.miller@wolpublishing.com:01/18/1980
John:Johnson:A:2155 North Street:Harrisburg:PA:17101:717-233-1100:john.johnson@wolpublishing.com:02/16/1967

I am having trouble with grep command in my function

Code:

function search_name {
addressfile=~/myaddrbook

    grep "$1" $addressfile | tr ":" " "
	echo
    	echo "listed above"
}

when i pass "$1" argument to grep command it list display whole file rather than specific record passed from the script command line.

[asistant@myserver ~]$ ./test3 John

any idea?

Thanks you.

grail · 04-17-2012, 10:36 AM

I would suggest putting set -xv just after the shebang and you will see the reason for this. As a nudge in the right direction, functions and scripts behave similarly when called with parameters

asistant · 04-17-2012, 10:38 AM

grail, sorry how do you do that?

Nominal Animal · 04-17-2012, 12:32 PM

Quote:

Originally Posted by grail

As a nudge in the right direction, functions and scripts behave similarly when called with parameters

Quite.

Put another way, $1 in a function refers to the first parameter to the function.

Bluntly: it does not refer to the first positional parameter the caller might have, as asistant seems to think. Functions only see their own positional parameters.

($0 is special, though: it describes the script name. For Bash sripts, it gets set to whatever file Bash is executing.)

grail · 04-17-2012, 12:57 PM

Quote:

grail, sorry how do you do that?

So the first 2 lines of the script should look like:

Code:

#!/bin/bash
set -xv

<rest of your script here>

asistant · 04-17-2012, 01:30 PM

thanks grail I am getting closer. Here is what happens

When i execute the script like this;

[asistant@myserver]$ ./test4 John

Code:

if [ -n "$1" ]; then
   search_name
fi
+ '[' -n John ']'
+ search_name
+ addressfile=/home/asistant/myaddrbook
+ grep '' /home/asistant/myaddrbook
Elizabeth:Miller:A:55 W. Main Street:Camp Hill:CA:94500:717-502-0334:elizabeth.miller@wolpublishing.com:01/18/1980
John:Johnson:A:2155 North Street:Harrisburg:PA:17101:717-233-1100:john.johnson@wolpublishing.com:02/16/1967
+ echo

It knows that i passed arguments John=$1 but inside the function it kind of clears $1 when i pass to $1 to grep command.

any ideas?

Thanks you.

grail · 04-17-2012, 03:03 PM

Quote:

any ideas?

Yes ... re-read posts #9 & 11 again carefully

asistant · 04-18-2012, 08:58 AM

thank for pointing me right direction. Here what i come up with.
added
#Make arguments global to the script.
args=("$@")

changed the function as;
#Create function for searching name.
function search_name {
addressfile=~/myaddrbook
grep -i ${args[0]} $addressfile | tr ":" " "
}

Here is my new version of the script.

Code:

#!/bin/bash
#
#Make arguments global to the script.
args=("$@")

#Create function for displaying help.
function display_help {
    echo "Usage: $0 [-a] [-b ] [<name>]";
        echo "OPTIONS:";
        echo "          [-a] Add record to address book";
        echo "          [-b] Send personalized greeting whose birthday is today";
        echo "          [<name>] search for specified name";
        exit 1
}

#Create function for searching name.
function search_name {
addressfile=~/myaddrbook
    grep -i ${args[0]} $addressfile | tr ":" " "
}

#Create function for adding new records.
function add_record {
    echo "Adding Record to database";
        echo "           [<name>] search for specified name"
}

#Create function for sending greetings.
function send_b_greetings {
    echo "Sending birthday greetings";
        echo " [<name>] search for specified name"
}


#If no argument or parameter specified dislplay help menu.
if [ $# -eq 0 ]; then
    display_help
fi

#Now parse command line arguments using getopts.
while getopts "ab" var;
do
    case "$var" in
        a) add_record; exit 0;;
        b) send_b_greetings; exit 0;;
        \?) display_help; exit 1;; 
    esac
done

search_name
exit 0

Thank you very much for your help.