UNIX for Dummies Questions & Answers

This might be a weird question, that's not possible, but just wondering:

If I have a file for example that has the content:

Code:

awk '{print "head - "$1" > reduce_lines_"$1}' all

And another file that has the content:

Code:

221

Is there a way to put the 221 in the space (after head -) of the first file (not having to do it manually because each file has a different number (221 is not constant) ?

Yea, you can use... AWK

Code:

awk 'NR==FNR{x=$0;next}{$4=$4x}1' file2 file1

What are the $0, $4 and $4x? If doing such things are possible then I would like to use it in many other cases
Does it only apply to one line files? What if the

Code:

head -

was part of a larger executable file?

$4 is the 4th column in file1. $4x is a string composed of 4th column and "x" variable attached to it. So $4=$4x means: attach string stored in "x" variable to the 4th column. "x" variable was initialized with the line from file2 (NR==FNR{x=$0;next}).

So that means it only applied to one line script files? Otherwise it will do that for each 4th column in the file.
I actually tried it for longer files but didn't get any output...

What are the sample files that you tried it on? Both file1 and file2.

I am trying for 2 cases:

Case1:

File1:

Code:

221

File2 is a long file and this is part of if:

Code:

# Then delete unwanted lines from ALL the files (data + model)
awk '{print "head -221 "$1" > reduce_lines_"$1}' all > Delete_zero_flux
chmod +x Delete_zero_flux
./Delete_zero_flux
ls reduce* > all_reduce