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Linux - Sort based on two field names

I have several txt files "file_i.txt" that look like this:

id, size, price, colour 
1, 2, 10, black
2, 8, 5, blue
...

All files contain these fields, but the order of the fields may be different.

I would like to sort each file based on two functions, first the price and then the size. I know that it is possible to use command sort to sort by two fields like this:

sort -k2,3 -k1,2 file_i.txt

However, since the position of the field is different in every file, is there a way to sort based on the field name?

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3 answers


Basically the command sort

should look like this:

sort -k3n -k2n input

where N

in -kN

- key number, and N

means sorting numeric.



sort

cannot be sorted by field names. You need to get the column number somehow. I use awk

for this:

kprice=$(awk -F', ' -vfield=price 'NR==1{for(i=1;i<=NF;i++){if($i==field){print i;exit}}}' a.txt)
ksize=$(awk -F', ' -vfield=size 'NR==1{for(i=1;i<=NF;i++){if($i==field){print i;exit}}}' a.txt)

sort -k"$kprice"n -k"$ksize"n a.txt
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I think you need to write the script yourself, say "mySort" and run like:

./mySort "id" "size"


Pseudocode, assuming the first line of the file contains the column name:

read input list
for each element in list, save the position (parsing first line)
apply sort
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you can do some preprocessing:

for each file:

  • transpose file
  • sort by first column (names)
  • return transpose

Then all columns will be ordered the same and you can use the standard sort

approach.

File transpose in bash is already allowed in other questions here: SO:

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