Using multiple sed commands for text manipulation

Question

I have a bash file, in which I would like to make several changes.

sed -i 's/      /    /g' testfile
sed -i -e 's/#[a-z]$//' -e '/^$/d' testfile
sed -i 's/ *$//' testfile
sed '/##=/ r header' testfile

In first command would like to replace TAB with spaces and after that remove comments(there are also comments, which begin with ##) and empty lines. After that would like to insert a file after a specified pattern in my file. Is there something wrong with command ordering?

Answer 1

you can give multiple instruction in one shot of sed, for example:

sed 's/\t/    /g;/^ *$/d;s/^#/NODIESE/' testfile

this single line

1. replace tab with space
2. delete line that start with empty stuff (or empty line)
3. replace Dash at start with the word NODIESE

so your test file is processed only once and you launch sed only one time.