Hi! Basically, I have 2 text files and need to combine them into one while making a few changes. The commands I came up with were too long/slow so I figured some more familiar with awk could help me.

Basically I have these 2 files, were N~50000 :

file1.res

1 a1 a2 ... a13
2 b1 b2 ... b13
.
.
.
N x1 x2 ... x13

and file2.res

1 aa1 aa2 ... aa13
2 bb1 bb2 ... bb13
.
.
.
N xx1 xx2 ... xx13

I need an output file of the form:

x1 a1 aa1 b1 bb1 ... x1 xx1
x2 a2 aa2 b2 bb2 ... x2 xx2
.
.
x13 a13 aa13 b13 bb13 ... x13 xx13


I manage to do it using intermediate files, but for really big N that's most inconvenient, so can anyone see a one-liner for this one?

I forgot to say x1 to x13 in the last table are headers, they're not part of any previous file.

Something like this?


Not sure it caters for your second comment about headers correctly... but should point you in the right direction.

Annihilannic
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Yo, thank you :) That's very helpful. It work and I also sorted the headers. I really augth to learn this awk thing better, it's quite impressive what it can achieve.

Thanks again! Could you just explain a detail to me please?

My file ended up with too many lines, so I added this command:

awk -v n=13 'NR>n{print a[NR%n]}{a[NR%n]=$0}'

to removes the last 13 lines, it works, but I would rather use

awk -v n=NR/2 'NR>n{print a[NR%n]}{a[NR%n]=$0}'

to remove half of the lines (might not always be 13 in the future). However an error message says it's trying to divide by 0... What's going on?

"-v n=NR/2" is processed only once before the main script is run, also it isn't interpreted as awk code, so you just end up with the text "NR/2" in the variable.

Also NR is a dynamic value; it increases as awk processes each line of input, so NR/2 would be a moving target.

If you are processing the file in 2 phases (like my example), then you'll need to calculate your equivalent to NR/2 in the END { ... } clause of the script, something like this:

Annihilannic
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That clarifies so many things. Thank you