How to add '\n' to the end of each line in a log file

Question

I'm using msmtp to create e-mail alerts on some RPi kiosks we have set up at my company, and unfortunately if I try to include the last 5 lines of a log file in the e-mail alert, msmtp doesn't handle the line breaks correctly and it prints all on a single line of text. If \n is included in each line in the log file, it outputs correctly in the e-mail alert.

A basic example for this command would be:

echo -e "This is a test. $(tail -5 /var/log/syslog)" | msmtp @domain

which does echo the syslog; yet it's all in one wall of text because msmtp doesn't seem to handle line breaks. If I manually edit the syslog and add \n to the end of each line, it prints properly

What's the proper syntax for sed or awk to add \n to the end of every line in a log file?

Answer 1

This is very simple. The input to msmtp is supposed to be a properly formatted mail message, with headers and body. It is, after all, another drop-in replacement for /usr/{bin,lib}/sendmail. You've not delimited headers from body, or indeed generated any headers at all. Your system log lines are being treated as (some very odd) headers.

headers. newline. body. Generate that.

Answer 2

My guess is that the mail tool is expecting \r\n. This is also the line endings used on Microsoft's products. (they (or maybe the writers of CP/M) did not know how to transform it when sending it to a printer, so as a work around made every file have this line ending. msmtp may have its own reasons.).

Therefore try piping it through unix2dos.

i.e.

echo -e "This is a test. $(tail -5 /var/log/syslog)" | unix2dos | msmtp @domain

Also unless you intend echo to interpret the log. I would do

{
  echo -n "This is a test. "
  tail -5 /var/log/syslog
} |
  unix2dos | 
  msmtp