bash script - how to setup a function to work with an embedded if statement

Question

I have the following working function in my bash script:

addMD5SUM()
{
file=$COLS2
linecount=$(wc -l $file | awk '{ print $1 }')
counter=1
while IFS='' read -r column; do
  case column in
    visitor_id)
       echo "isnull($column|| '[|]' ||";;
       updated)
       echo "isnull($column::text || '[|]' ||";;
             *)
       echo "isnull($column::text,'[null!]') || '[|]' ||";;
  esac
  if [ "$counter" -eq "$linecount" ]; then
      echo "isnull($column::text,'[null!]')) as md5sum"
  fi
  ((counter++))
done <"$file"
}

Where $COL2 is a single filename:

COLS2="myoutputfile2.out"

Contents of this file would be something like:

visitor_id
updated
visitor_list_1
visitor_list_2
visitor_list_3
visitor_list_4
visitor_list_5

Other files would be similar: (i.e.)

visitor_id
updated
visitor_list_6
visitor_list_7
visitor_list_8
visitor_list_9
visitor_list_10

Now, I need to alter this function so that I have the option to have it work with either one of these files:

export COLS1="myoutputfile1.out"
export COLS2="myoutputfile2.out"
export COLS3="myoutputfile3.out"
export COLS4="myoutputfile4.out"

How would you do this? Would you do this as an if-statement? What is the best and proper way to do handle this?

Please post the example sample Input_file and expected sample output too in your post. — RavinderSingh13
– RavinderSingh13, Commented Jan 26, 2018 at 6:48

Diego Torres Milano · Accepted Answer · 2018-01-26 06:48:27Z

2

Send the COLSn as a parameter to the function

addMD5SUM()
{
  file="$1"
  ...
}

then

addMD5SUM $COLS1
addMD5SUM $COLS2
...

answered Jan 26, 2018 at 6:48

Diego Torres Milano

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1 Comment

noober Over a year ago

Awesome! thank you. That makes sense and was simple enough.

iBug · Accepted Answer · 2018-01-26 06:49:45Z

0

Use the ~~evil~~ eval to let Bash parse the variable for an extra pass.

export COLS1="myoutputfile1.out"
export COLS2="myoutputfile2.out"
export COLS3="myoutputfile3.out"
export COLS4="myoutputfile4.out"

addMD5SUM()
{
eval file=\$$1
...

And call the new function like

addMD5SUM COLS1
addMD5SUM COLS2
addMD5SUM COLS3
addMD5SUM COLS4

answered Jan 26, 2018 at 6:49

iBug

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Comments

sjsam · Accepted Answer · 2018-01-26 07:38:50Z

0

As said in the accepted answer, you can send an argument to the function but user supplied arguments shouldn't be trusted.

Since your files have a format, you could do something like below

file=${1:-0} # If the argument 1 is not present, assign zero to file
! [[ "${file}" =~ myoutputfile[0-9]+.out ]] || ! [ -f "${file}" ] &&
echo "Invalid parameter" && exit 1

answered Jan 26, 2018 at 7:38

sjsam

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