How to sort a file with a bash script using sort and getopts?

Question

This is my bash script that sorts a file by columns.

while getopts "123456" flag

do
sort -t: -k $flag names.txt

done

Right now it does exactly what I need, but I need to have the filename be a parameter too.

The input right now is ./sortScrpt -2.

I need the input to look like ./sortScript -2 names.txt

Any help would be great. Thanks

Answer 1

Change your bash script to:

while getopts "123456" flag

do
sort -t: -k $flag "${2}"

done

Getting parameters you can use "${2}" for the second parameter

Answer 2

Something to get you started:

#!/bin/bash

while getopts ":2:" opt; do
  case $opt in
    2)
      echo "-2 was triggered, Parameter: $OPTARG" >&2
      ;;
    \?)
      echo "Invalid option: -$OPTARG" >&2
      exit 1
      ;;
    :)
      echo "Option -$OPTARG requires an argument." >&2
      exit 1
      ;;
  esac
done

output:

$ ./a.sh -2 names.txt
-2 was triggered, Parameter: names.txt

Answer 3

If you want multiple sort parameters then you can update your script as:

#first parse -f fname    
getopts "f:" f
fname=$OPTARG

while getopts "123456" flag

do
    sort -t: -k $flag $fname
done

You can run this script as

$ ./script.sh -f names.txt -2 

or for multiple sorts

$ ./script.sh -f names.txt -2 -3 

Answer 4

EDIT revised for "sort-arg then file" requirement + error checking:

#!/bin/bash

sflag=""
sfile=""

while getopts "123456" flag
do
        [ -z "$sflag" ] && sflag="$flag"
done
shift $(($OPTIND - 1))
sfile="$1"

if [[ "$sflag" ]] && [[ "$sfile" ]];
then
    sort -t: -k $sflag $sfile
else
    # error - bail out
    echo "usage: $0 -[123456] file.txt" >&2
    exit 1
fi

OPTIND is set by getopts and will either point to $#+1 (e.g. no extra parameters) or to the first parameter not matching your getopts-flags.