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Bash: Is there a more elegant way to write if statement

My bash script takes 3,5,7,9 or 11 arguments, a file name and a start and stop point to cut from the file, up to five start and stop points, so this is what I've constructed, is there a more elegant way:

Code:

#!/bin/bash

renice 19 -p $$

if [[ $# -eq 3 ]] || [[ $# -eq 5 ]] || [[ $# -eq 7 ]] || [[ $# -eq 9 ]] || [[ $# -eq 11 ]] ; then

:

else

    echo "====================================================================="

    echo "Please enter the Input file name start point and duration in hh:mm:ss"

    echo "Example: abc.mts 12:00 15:00 i.e. starts at 12 min and ends at 15 min"

    echo "You can have up to 5 cuts from a single file"

    echo "====================================================================="

    exit 1

fi



echo "No of parameters: $#"

echo "Processing file $1"

echo "start at $2"

echo "end at $3"



exit 0

Okay there is no actual processing code, I just want to get the framework of the script done. It works like this,

No Parameters:

Code:

jonke@charlie:~$ HB-Cutter.sh

11316 (process ID) old priority 0, new priority 19

=====================================================================

Please enter the Input file name start point and duration in hh:mm:ss

Example: abc.mts 12:00 15:00 i.e. starts at 12 min and ends at 15 min

You can have up to 5 cuts from a single file.

=====================================================================

jonke@charlie:~$

Three arguments:

Code:

jonke@charlie:~$ HB-Cutter.sh abc.mp4 12:24 15:30

11321 (process ID) old priority 0, new priority 19

No of parameters: 3

Processing file abc.mp4

start at 12:24

end at 15:30

jonke@charlie:~$

Four arguments:

Code:

jonke@charlie:~$ HB-Cutter.sh abc.mp4 12:24 15:30 18:20

11335 (process ID) old priority 0, new priority 19

=====================================================================

Please enter the Input file name start point and duration in hh:mm:ss

Example: abc.mts 12:00 15:00 i.e. starts at 12 min and ends at 15 min

You can have up to 5 cuts from a single file

=====================================================================

jonke@charlie:~$

Five arguments:

Code:

jonke@charlie:~$ HB-Cutter.sh abc.mp4 12:24 15:30 18:20 20:36

12065 (process ID) old priority 0, new priority 19

No of parameters: 5

Processing file abc.mp4

start at 12:24

end at 15:30

jonke@charlie:~$

and yes, I've not printed the 4th and 5th argument, but when finished the script will process them

There are many ways... getopts is the bash builtin command to parse command line options.

Code:

#!/bin/bash

declare -a start

declare -a duration



a=$#

b=$((a-1))

n=$((b%2))



if [[ $n != 0 || $a -gt 11 ]]; then

  echo 'invalid argument list'

  #...... 

  exit

fi



shift 1

i=$((b/2))

for (( c=1; c<=i; c++))

do

    echo "$1,$2"

    start+=($1)

    duration+=($2)

    shift 2

done

echo ${start[@]}

echo ${duration[@]}

Not sure about more elegant but easier to manage number of time segments.

Hope this snipped will give you some pointers

Code:

echo file $1

shift

while [ $# != 0 ]; do

  echo start $1

  echo end $2

  shift 2

done

Thanks guys, I've used getopts in other scripts, just trying something different, but it's a good suggestion as is the shift method.

I think I might go down the shift method, that'll allow me any number of cuts.

Note: I'm a product of the 1970's, cut my teeth on Fortran IV on IBM 360 machines.....

"say no more" as they said in Monty Python!

Quote:

Originally Posted by GPGAgent (Post 6253185)

Code:

#!/bin/bash

renice 19 -p $$

if [[ $# -eq 3 ]] || [[ $# -eq 5 ]] || [[ $# -eq 7 ]] || [[ $# -eq 9 ]] || [[ $# -eq 11 ]] ; then

:

else



<snip>

Instead of a gory if-then, there's case-esac:

Code:

#!/bin/bash



NARGS=$#



case ${NARGS} in

    3 | 5 | 7 | 11)

        FILE=$1; shift

        while [ $# -gt 0 ]

        do

            START=$1; shift

            STOP=$1; shift

        #  Act on $FILE

        done

        ;;

    *)

        echo "Wrong number of args."

        exit 1

esac

HTH...

If one branch exits then you can leave the other branch empty.

Code:

case ${NARGS} in

( 3 | 5 | 7 | 11 )

;;

( * )

    echo "Wrong number of args."

    exit 1

esac

FILE=$1; shift

while [ $# -gt 0 ]

do

    START=$1; shift

    STOP=$1; shift

#  Act on $FILE

done

A tricky alternative to the case-esac is

Code:

if [[ " 3 5 7 9 11 " != *" ${NARGS} "* ]]

then

    echo "Wrong number of args."

    exit 1

fi