bash shell scripting transpose rows and columns

Question

I need help transposing a file that just simply has some numbers in them with rows and columns. I can't use awk shell or perl so it makes it kind of hard. I've been working on it for a couple of hours and can't get it working correctly. I tried a couple of other things but this is what I have right now. It runs, but it doesn't print out anything, so that leads me to conclude that something is wrong within my code. Also if you dont know by transpose if a file had :

1 2 3 
4 5 6

... it would then print out

1 4
2 5
3 6

Here is my code:

if [ $# -gt 2 ]
then
  echo"System error">&2
exit 1

elif [[ $# -eq 2 && -e "$2" && -r "$2" ]]
then 
while read -a line; do
    for ((i=0; i < "${#line[@]}"; i++)); do
        a[$i]="${a[$i]} ${line[$i]}"
    done
done < $2

for ((i=0; i < ${#a[@]}; i++)); do
    echo ${a[i]}
done


fi

It works for me (except that the $# -gt 2 condition needs a space between echo and the message). How are you running it (and what arguments are you passing)? — Gordon Davisson
– Gordon Davisson, Commented Oct 10, 2019 at 5:17
Thank you for the reply. so when I go to run this script I go: matrix transpose m1... which matrix is the name of this file, tranpsose is this function and then m1 is just a text file containing numbers I need to tranpsose. Thank you for the reply — user12179064
– user12179064, Commented Oct 10, 2019 at 5:19
That sounds like it should work. I'd try putting set -x before the problem section, so you can see what's happening as it runs. — Gordon Davisson
– Gordon Davisson, Commented Oct 10, 2019 at 5:22
Where exactly do you mean in needs space? are you referring too the echo" system failure" because that doesn't really do anything — user12179064
– user12179064, Commented Oct 10, 2019 at 5:24
Yes, it should be echo "system failure" -- try both with and without the space, and compare the results. — Gordon Davisson
– Gordon Davisson, Commented Oct 10, 2019 at 5:26

Šerg · Accepted Answer · 2019-10-10 06:54:59Z

2

If possible use awk:

Source (file.txt):

1 2 3
4 5 6

Result:

1 4
2 5
3 6

Oneline awk sctript:

awk '{ for (i=1; i<=NF; i++) a[i]= (a[i]? a[i] FS $i: $i) } END{ for (i in a) print a[i] }' file.txt

It works same with

1 2 3         1 4 7
4 5 6    ->   2 5
7             3 6

and with

1 2 3 4       1 5
5 6 7    ->   2 6
              3 7
              4

answered Oct 10, 2019 at 6:54

Šerg

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1 Comment

stephanmg Over a year ago

Great solution. Should be accepted.

Toby Speight · Accepted Answer · 2019-10-10 16:07:22Z

1

Instead of writing a Bash function, we could use rs, written specifically for reshaping matrices. This command does exactly what you ask for:

rs -T

answered Oct 10, 2019 at 16:07

Toby Speight

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3 Comments

stephanmg Over a year ago

But this has to be installed, right? So the awk solution might fit better.

Toby Speight Over a year ago

Well, yes - but it's such a useful tool, it's worth getting your sysadmin to install it everywhere!

stephanmg Over a year ago

Okay, it might be worth to install it. If reshaping matrices will become a common task for me I will consider rs. Thanks!

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