changing a variable length text to a fixed length

Shell Programming and Scripting
1

Hi,
Can anyone help with a effective solution ?

I need to change a variable length text field (between 1 - 18 characters) to a fixed length text of 18 characters with the unused portion, at the end, filled with spaces.

The text field is actually field 10 of a .csv file however I could cut out the field if it makes it easier.

Thanks
Dave

2

How about printf?

$ X=abc
$ printf "%-18s" $X
abc               $

so...

$ X=$(printf "%-18s" $X)

You need to change the 10th field in every row to 18 characters?

$ cat file1.csv
1,2,3,4,5,6,7,8,9,10,11,12
a,b,c,d,e,f,g,h,i,j,k,l

$ awk -F, 'BEGIN {OFS=FS} {$10 = sprintf( "%-18s", $10 )}1' file1.csv
1,2,3,4,5,6,7,8,9,10                ,11,12
a,b,c,d,e,f,g,h,i,j                 ,k,l
4

Hi Scott,
You mention 'change the 10th column' , I need to change the 10th field in the .csv file (the actual start column of field 10 will vary) .... does your solution still apply ?
Dave

5

Hi.

Actually, I meant to say field.

I would normally say field, but somehow said column :slight_smile: (so, yes!)

I updated my earlier post to remove the confusion.

1 Like
6

Hi Scott,

I'm afraid your solution only works if there there are no spaces within the text ......... each space found within the text is also padded out to 18 spaces

Dave

7

Hi.

I don't see this. Can you post an example input that shows this behaviour?

Thanks.

8

Hi Scott,

Input file

01,10,000020,*,*,******,999999,00,,WERK 28 - BUS
01,10,000030,*,*,******,999999,00,,WERK 30 - UNIMOG
01,10,000060,*,*,******,999999,20,,LASTWAGEN
01,10,000065,*,*,******,999999,00,,WERK 65 - TRANSP.
01,00,000001,*,*,******,999999,00,,DB-PKW
01,00,000010,*,*,******,999999,00,,DB-LKW
01,00,100012,*,*,******,999999,20,,600
01,00,100014,*,*,******,999999,20,,600 LANG 4-T RIG
01,00,100015,*,*,******,999999,20,,600 LANDAUER
01,00,100016,*,*,******,999999,20,,600 LANG 6-T RIG

Output from script, before and after, showing field length & text

   b4 change 13    WERK 28 - BUS
after change 72    WERK              28                -                 BUS
   b4 change 16    WERK 30 - UNIMOG
after change 72    WERK              30                -                 UNIMOG
     b4 change 9    LASTWAGEN
after change 18    LASTWAGEN
   b4 change 17    WERK 65 - TRANSP.
after change 72    WERK              65                -                 TRANSP.
     b4 change 6    DB-PKW
after change 18    DB-PKW
     b4 change 6    DB-LKW
after change 18    DB-LKW
     b4 change 3    600
after change 18    600
   b4 change 16    600 LANG 4-T RIG
after change 72    600               LANG              4-T               RIG
   b4 change 12    600 LANDAUER
after change 36    600               LANDAUER
   b4 change 16    600 LANG 6-T RIG
after change 72    600               LANG              6-T               RIG

Shell Script

cat infile | while read line
do
  field=`echo $line | cut -d',' -f10`
  echo "   b4 change ${#field}    $field"
  field=$(printf "%-18s" $field)
  echo "after change ${#field}    $field"
done

Thanks
Dave

9 
while read line
do
  field=`echo $line | cut -d',' -f10`
  echo "   b4 change ${#field}    $field"
  field=$(printf "%-18s" "$field")
  echo "after change ${#field}    $field"
done < file1

   b4 change 13    WERK 28 - BUS
after change 18    WERK 28 - BUS
   b4 change 16    WERK 30 - UNIMOG
after change 18    WERK 30 - UNIMOG
   b4 change 9    LASTWAGEN
after change 18    LASTWAGEN
   b4 change 17    WERK 65 - TRANSP.
after change 18    WERK 65 - TRANSP.
   b4 change 6    DB-PKW
after change 18    DB-PKW
   b4 change 6    DB-LKW
after change 18    DB-LKW
   b4 change 3    600
after change 18    600
   b4 change 16    600 LANG 4-T RIG
after change 18    600 LANG 4-T RIG
   b4 change 12    600 LANDAUER
after change 18    600 LANDAUER
   b4 change 16    600 LANG 6-T RIG
after change 18    600 LANG 6-T RIG

If you don't quote $field, then the printf will apply the formatting (%-18s) to each part of $field, as separated by whitespace. By quoting it, the printf takes it as one argument.

$ a="1 2 3"
$ a=$(printf "%-18s" $a)
$ echo ${#a}
54

$ a="1 2 3"
$ a=$(printf "%-18s" "$a")
$ echo ${#a}
18
1 Like