bash: how do I write base64-encoded content into a file to specified line

Question

I'm working on an "edgemax feature-wizard" which is kind of a plugin system. There are only three files allowed in a plugin tarball: a bash script as backend, a HTML file as frontend and a validation.json file for input validation from frontend, so please don't ask why I don't just put the deb packages into the tarball -- they get ignored.

I want to ship deb packages with that "wizard" so I have to base64 encode the files and put it into the bash script to be extracted when the script is run. Now, I know how to do all this, but I'm doing it manually by copy-pasting the base64 part into the bash file and then cut-paste into right position, which is unhandy when updating those packages to recent version.

Would there be a possibility to encode the deb files in base64 and write it to line 65 of the bash script?

I've read this article and I tried

sed -i "65i\\$(base64 package.deb)" wizard-run

but that complains with:

bash: /bin/sed: Argument list too long

Here's my code; the base64-part has to go within the double-quotes from the echo statement:

if [ $arch == 'mips' ]; then
    # base64: olsrd_0.9.0.3-1_mips.deb
    echo "
    <base64encoded-pkg>
    " | base64 -d > $cfgusrdir/olsrd_0.9.0.3-1_mips.deb
    # base64: olsrd-plugins_0.9.0.3-1_mips.deb
    echo "
    <base64encoded-pkg>
    " | base64 -d > $cfgusrdir/olsrd-plugins_0.9.0.3-1_mips.deb
fi

+1 to the heredoc - however, at least if you have GNU sed, you could probably do `base64 package.deb | sed -i '65r /dev/stdin' wizard-run` — steeldriver, Oct 24 '16 at 20:27
great, that did it, thanks! is there a way to also remove newline at the end? — Christoph Lösch, Oct 24 '16 at 21:26

phk · Accepted Answer · 2016-10-24T21:32:51.653

2

Using sed and I/O redirection:

{
  sed -n '1,64p' wizard-run;
  base64 package.deb;
  sed -n '66,$p' wizard-run;
} > wizard-run.tmp && mv wizard-run.tmp wizard-run

edited Oct 24 '16 at 21:32

answered Oct 24 '16 at 19:54

phk

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good idea, but i dont understand why, that fills the wizard-run with the base64 part running in loop until i press ctrl+c .. – Christoph Lösch Oct 24 '16 at 21:01
1

@vchrizz Oops, writing to the file you are writing to is a bad idea (see https://github.com/koalaman/shellcheck/wiki/SC2094). My bad, will fix it. – phk Oct 24 '16 at 21:32
ok that worked now, how do i remove newline from beginning and end? – Christoph Lösch Oct 24 '16 at 21:52
@vchrizz Beginning and end of what? `wizard-run`? – phk Oct 24 '16 at 22:21
ive added my code to clarify. at the moment the line is beeing replaced by the base64 and it has to be within the quotes without newlines and/or spaces for the script to work. – Christoph Lösch Oct 24 '16 at 22:26
1

@vchrizz Try the `-i` parameter of `base64`. – phk Oct 24 '16 at 22:30

bash: how do I write base64-encoded content into a file to specified line

1 Answers1