Question regarding getopts...

ddenial · 09-02-2018, 10:12 AM

Hello

I want to use options in my script and want to execute like this.

Code:

myscript -o a input.file output.file

Where -o is some mandatory option.

Following is my script:

Code:

#!/bin/bash

ShowHelp() {
  echo "Some help"
}

MyFunction() {
  echo "\$1 = $1"
  echo "\$2 = $2"
  echo "\$3 = $3"
}

while getopts ":ho:" opt ; do
  case $opt in
    h)  
      ShowHelp
      ;;  
    o)  
      MyFunction "$OPTARG"
      ;;  
    \?) 
      echo "Invalid option: -$OPTARG"
      ;;  
    :)  
      echo "Option -$OPTARG requires an argument."
      exit 1
      ;;  
  esac
done

These are the results:

Code:

$ test.sh -a
Invalid option: -a

$ test.sh -o
Option -o requires an argument.

$ test.sh -o a
$1 = a
$2 = 
$3 = 

$ test.sh -oa
$1 = a
$2 = 
$3 =

So far so good. But if I add $2 (input.file) and $3 (output.file) , then results will be strange.

Changes in my script:

Code:

.
.

    o)  
      MyFunction "$OPTARG" "$2" "$3"
.
.

Result:

Code:

$ test.sh -oa input.file output.file
$1 = a
$2 = input.file
$3 = output.file

$ test.sh -o a input.file output.file
$1 = a
$2 = a
$3 = input.file

As you can see from the results, $1 will always be a, doesn't matter there is a space in between option or not. But $2 and $3 will have different values based on that space between the option and its argument. I don't want this to happen.

I want $1 $2 and $3 to hold same values irrespective of there is space or not in between them.

Code:

$ test.sh -oa input.file output.file
$ test.sh -o a input.file output.file

..be same.

How to do it?

Any help really appreciated.

Thanks

lougavulin · 09-02-2018, 11:08 AM

Your input and output files parameters are script parameters and not arguments of -o option.

So, you have to manage all your options and launch your function after.

Code:

#!/bin/bash

ShowHelp() {
  echo "Some help"
}

MyFunction() {
  echo "\$1 = $1"
  echo "\$2 = $2"
  echo "\$3 = $3"
}

while getopts ":ho:" opt ; do
  case $opt in
    h)
      ShowHelp
      ;;
    o)
      Oarg=$OPTARG
      ;;
    \?)
      echo "Invalid option: -$OPTARG"
      ;;
    :)
      echo "Option -$OPTARG requires an argument."
      exit 1
      ;;
  esac
done
shift $((OPTIND-1))

MyFunction "$Oarg" "$1" "$2"

Code:

bash toto -h -oa Un Deux

And

Code:

bash toto -h -o a Un Deux

Returns :

Code:

Some help
$1 = a
$2 = Un
$3 = Deux

ddenial · 09-02-2018, 11:35 AM

Quote:

Originally Posted by lougavulin

Your input and output files parameters are script parameters and not arguments of -o option.

So, you have to manage all your options and launch your function after.

Code:

#!/bin/bash

ShowHelp() {
  echo "Some help"
}

MyFunction() {
  echo "\$1 = $1"
  echo "\$2 = $2"
  echo "\$3 = $3"
}

while getopts ":ho:" opt ; do
  case $opt in
    h)
      ShowHelp
      ;;
    o)
      Oarg=$OPTARG
      ;;
    \?)
      echo "Invalid option: -$OPTARG"
      ;;
    :)
      echo "Option -$OPTARG requires an argument."
      exit 1
      ;;
  esac
done
shift $((OPTIND-1))

MyFunction "$Oarg" "$1" "$2"

Code:

bash toto -h -oa Un Deux

And

Code:

bash toto -h -o a Un Deux

Returns :

Code:

Some help
$1 = a
$2 = Un
$3 = Deux

Oh! Now I understand.

Is this right way then,

Code:

#!/bin/bash

ShowHelp() {
  echo "Some help"
}

MyFunction() {
  echo "\$1 = $1"
  echo "\$2 = $2"
  echo "\$3 = $3"
}

while getopts ":ho:" opt ; do
  case $opt in
    h)  
      ShowHelp
      ;;  
    o)  
      ARG="$OPTARG"
      ;;  
    \?) 
      echo "Invalid option: -$OPTARG"
      ;;  
    :)  
      echo "Option -$OPTARG requires an argument."
      exit 1
      ;;  
  esac
done
shift $((OPTIND-1))

if [[ $ARG == "a" ]] ; then
  MyFunction "$ARG" "$1" "$2"

elif [[ $ARG == "b" ]] ; then
  MyFunction "$ARG" "$1" "$2"

else
  echo "Argument should be 'a' or 'b'"
fi

michaelk · 09-02-2018, 12:54 PM

It doesn't work like you think it does.

getopt finds the argument of the option regardless if there is a space between them i.e -oa or -o a.

The difference between -oa and -o a is that bash considers -oa as one command line argument versus -o a as two. I Will ignore the case of using quotes in command line arguments...

$1 will always be the first command line argument regardless. getops will stop when it can not find any more hyphens (-).

To make things simple I might suggest using an option for the input file and assume that the last command line argument is the output file.

lougavulin · 09-02-2018, 01:01 PM

Quote:

Originally Posted by michaelk

To make things simple I might suggest using an option for the input file and assume that the last command line argument is the output file.

Yes, that would be better and according how many options OP wants for his script, that will help a lot.

ddenial · 09-02-2018, 02:50 PM

While in the script I'm writing there will be several options, but only one option will be used at any given time. That could be with no argument or one argument.

Something like this:

Code:

script -h                      # Show help

script -l {a,h,x}              # -la => show all video files. 
                                 -lh => show video files with hevc codec. 
                                 -lx => show video files which are not hevc

script -c {n,h,f} input output # -cn => Convert, Normal, dont change resolution, 
                                 -ch => Convert to HD 
                                 -cf => Convert to Full HD

script -r {n,h,f}              # Resursively convert all videos and replace with same name in a directory.
                                 Arguments same as above.

michaelk · 09-02-2018, 03:43 PM

shift $((OPTIND-1))

The above command basically will shift the position of the cli arguments so now $1 will be the first remaining argument that isn't an option, $2 the next. You can parse them for your input and output file names.