mjhjmtu

What does awk 'print $1+0.45 " " $2 " " $3 ' positionXYZ > positionX0.45YZ
mean? Does it mean changing a row in the first file and put the new data into the second one?

Let's break this down. awk 'foo' file will apply the expression foo to each line of file and print the result to the terminal (standard output). awk splits its input lines on white space (by default) and saves each field as $1, $2 etc.

So, the actual expression you are running means: read each input line, add 0.45 to the value of the first field and then print that field as well as the second and third one. This is most easily explained with a simple example:

$ cat file.txt 
10 20 30 40
50 60 70 80

$ awk 'print $1+0.45 " " $2 " " $3 ' file.txt 
10.45 20 30
50.45 60 70

So, as you can see, the awk script added 0.45 to the first field of each line and then printed it along with the second and third. The fourth was ignored since you did not tell it to print $4.

The next bit has nothing to do with awk, the > symbol is for output redirection and is used by the shell (bash or zsh or whatever you are using). In general command > file will save the output of command in the file file overwriting the contents of the file if it exists and creating it if it does not.

Putting everything together:

$ ls
file.txt

$ cat file.txt 
10 20 30 40
50 60 70 80

$ awk 'print $1+0.45 " " $2 " " $3 ' file.txt > file2.txt

$ ls
file2.txt file.txt

$ cat file2.txt 
10.45 20 30
50.45 60 70

file2 has 0.45 added to each value of first column (the x'es), column 2 and 3 are copied as is, anything else on the line is ignored.

awk reads each line of file1 and runs the script between

The script is run on every line, white spaced delimitered fields are assigned to positional parameters $1, $2 $3, ...

The parameters are printed except $1 is added with 0.45