Question

I need to use bash to insert a line into a python file. This line needs to appear after any initial comments in the the file.

So given the file:

#!/usr/bin/python
# This is just 
# an example comment

moo = "cow"
... etc ...

I need a bash command to insert a new line like this:

#!/usr/bin/python
# This is just 
# an example comment
NEW LINE GOES HERE

moo = "cow"
... etc ...

I am entirely stumped on how to do this. I have tried looping over the file line by line, but that just ends up being pretty horrific and severely messing up the file’s whitespace.

Any suggestions would be great!

Adam

PS. Yes, this is a bit of a weird thing to do, it is for part of a continuous integration build script.

---

Edit

For the record, the code I was trying was:

insert_setup_code() {
    installed=false
    tmpfile="/tmp/$RANDOM"

    cat "$INSTALL_TO" | while read -d \n l; do
        echo "$l" >> $tmpfile
        if [[ ! $installed && ! `echo "$l" | grep "^#"` ]]; then
            echo "LINE OF CODE HERE" >> $tmpfile
            installed=true
        fi
    done
}

Answer 1

I would write:

line="NEW STUFF HERE"
awk -v text="$line" '!/^#/ && !p {print text; p=1} 1' file

The first non-comment line will trigger the block to print the line:

• !/^#/ — line does not start with a hash
• !p — variable p is not true