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linuxsed

Sed line when matching some string and not another one with sed

Struggling again.

I would like to add a line right after another one when matching some pattern and not a another one.

Here's my input file :

# abc def hello
# bye hello zzzz
# abc def hello

Expected output is :

# abc def hello
new line
# bye hello zzzz
# abc def hello
new line

I want to add a line after any line of a file that starts with #, contains the word hello but not bye

I read about some exclusion possibility with sed (i.e \*<kbd>/pattern/!</kbd> \*) but haven't managed to add it to command so far.

Thanks!

sed -e '/^#.\*hello.\*/Ia\\'"new line" $input_file

where can the /bye/! thingy be included to this?

Solution

  • where can the /bye/! thingy be included to this?

    Sed is a programming language, technically. Start a block and check within.

    The real issue is that a reads the whole next line. So you have to like start another one to close }.

    sed -e '/^#.*hello.*/I{ /bye/!a\' -e "new line" -e '}' "$input_file"

    The syntax of a command is:

    a\
text

    Technically, there has to be newline in the sed script for text. I see a\text works anyway, but technically it is not valid. GNU sed also allows for just a text.

    Prefer to quote variable expansion in shell. Check your scripts with shellcheck.