How to take multiple argument in bash and pass them to awk?

Question

I am writing a function in which I am replacing the leading/trailing space from the column and if there is no value in the column replace it with null. Function is working fine for one column but how can i modify it for multiple columns.

Function :

#cat trimfunction
#!/bin/bash
function trim
{
vCol=$1                                                    ###input column name
vFile=$2                                                   ###input file name
var3=/home/vipin/temp                                      ###temp file
awk -v col="${vCol}" -f /home/vipin/colf.awk ${vFile} > $var3 ###operation
mv -f $var3 $vFile                                         ###Forcefully mv
}

AWK script :

#cat colf.awk
#!/bin/awk -f
BEGIN{FS=OFS="|"}{
  gsub(/^[ \t]+|[ \t]+$/, "", $col)                        ###replace space from 2nd column
}
{if ($col=="") {print $1,"NULL",$3} else print $0}         ###replace whitespace with NULL

Input file : leading/trailing/white space in 2nd column

#cat filename.txt
1| 2016-01|00000321|12
2|2016-02 |000000432|13
3|2017-03 |000004312|54
4|  |000005|32
5|2017-05|00000543|12

Script :

#cat script.sh

    . /home/vipin/trimfunction
    trim 2 filename.txt

Output file : leading/trailing/white space removed in 2nd column

#./script.sh
#cat filename.txt
1|2016-01|00000321|12
2|2016-02|000000432|13
3|2017-03|000004312|54
4|NULL|000005
5|2017-05|00000543|12

If input file is like below - ( white/leading/trailing space in 2nd and 5th column of file)

1|2016-01|00000321|12|2016-01 |00000
2|2016-02 |000000432|13| 2016-01|00000
3| 2017-03|000004312|54|  |00000
4|  |000005|2016-02|0000
5|2017-05 |00000543|12|2016-02 |0000

How to achive below output - (All leading/trailing space trimmed and white space replaced with NULL in 2nd and 5th col) something like trim 2 5 filename.txt trim 2 5 filename.txt ###passing two column name as input

1|2016-01|00000321|12|2016-01|00000
2|2016-02|000000432|13|2016-01|00000
3|2017-03|000004312|54|NULL|00000
4|NULL|000005|2016-02|0000
5|2017-05|00000543|12|2016-02|0000

Answer 1

This will do what you said you wanted:

$ cat tst.sh
file="${!#}"
cols=( "$@" )
unset cols[$(( $# - 1 ))]

awk -v cols="${cols[*]}" '
BEGIN {
    split(cols,c)
    FS=OFS="|"
}
{
    for (i in c) {
        gsub(/^[[:space:]]+|[[:space:]]+$/,"",$(c[i]))
        sub(/^$/,"NULL",$(c[i]))
    }
    print
}' "$file"

$ ./tst.sh 2 5 file
1|2016-01|00000321|12|2016-01|00000
2|2016-02|000000432|13|2016-01|00000
3|2017-03|000004312|54|NULL|00000
4|NULL|000005|2016-02|0000
5|2017-05|00000543|12|2016-02|0000

but if what you REALLY wanted was to operate on ALL fields instead of specific ones then of course there's a simpler solution.

Never do cmd file > tmp; mv tmp file by the way, always do cmd file > tmp && mv tmp file instead (note the &&) so you only overwrite your original file if the command succeeded. Also - always quote your shell variables unless you have a very specific purpose in mind by not doing so and fully understand all of the implications, so use "$file", not $file. Google it.

Answer 2

You can pass a list of columns to modify as a parameter. Create files

$ cat trim.awk

BEGIN {
    split(c, a)
    FS = OFS = "|"
}

{
    for (i in a) {
        i = a[i]
        gsub(/^[ \t]+|[ \t]+$/, "", $i)
        if (!length($i)) $i = "NULL"
    }
    print
}

and

$ cat filename.txt

1|2016-01|00000321|12|2016-01 |00000
2|2016-02 |000000432|13| 2016-01|00000
3| 2017-03|000004312|54|  |00000
4|  |000005|2016-02|0000
5|2017-05 |00000543|12|2016-02 |0000

Usage:

awk -v c="2 5" -f trim.awk filename.txt 

Answer 3

If managing leading/trailing spaces is all you want to do, you probably don't want to do all(AWK code) that.

cat q1.txt | tr -s ' ' | sed 's/|\ |/|NULL|/g' | sed 's/\ //g' should do.

Break-down
tr -s ' ' : Squeeze multiple spaces into one
sed 's/|\ |/|NULL|/g' : Replace all "| |" with "|NULL|"
sed 's/\ //g' : Replace all spaces with empty string.