using Linux shell script to edit and rename a file

Question

I am trying to execute a command using Vi or ex to edit a file by deleting the first five lines, replace x with y, remove extra spaces at the end of each line but retain the carraige returns, and remove the last eight lines of the file, then rename the file into a shell script and run the new script from the current script.

This will be something that is scheduled in cron. I have been looking for a simple way to do it using the command line or a Vim script or something.

Any ideas? The format of the input file does not change, just the amount of lines, so I can't specify the line numbers for the last eight lines.

Answer 1

To edit a file by a script, you could use ed (even if it hard to learn or remember).

You could also use some scripting language (Python, Perl, AWK, Ruby) to achieve your goal.

Answer 2

You actually have about half a dozen questions here. Here's an answer for the first five which are probably the ones you'll have the most difficulty solving:

sed -e ':label' -n -e '1d' -e 's/x/y/g' -e 's/[ \t]*$//g' -e '1,9!{P;N;D};N;b label' file.txt > script.sh

Answer 3

Vi is an interactive editor. You probably don't want to use it for something that'll be run by cron. Also, I agree with the comments saying this is probably a bad idea. Be that as it may:

printf 'one\ntwo\nthree\nfour\nfive\necho x \n1\n2\n3\n4\n5\n6\n7\n8\n' \
| sed '1,5d;s/  *$//;s/x/y/' \
| tail -r | sed 1,8d | tail -r \
| sh

Our first sed script does most of the work. We reverse the lines with tail -r, then delete the first 8 lines, then reverse again. That trims off the last 8 lines.

Note that on Linux systems (or any with GNU coreutils), you may also have a tac command which reverse lines, but tail -r is more portable.

Also, the final | sh simply runs the output. If you REALLY want to save this as a script, you can do that by redirecting the output to a file ... but I'll leave at least that to your imagination. Can't do all your scripting for you, can we?! :-)