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diff --git a/_tils/2021-01-12-awk-snippet-send-email-to-multiple-recipients-with-curl.md b/_tils/2021-01-12-awk-snippet-send-email-to-multiple-recipients-with-curl.md deleted file mode 100644 index 880ddf1..0000000 --- a/_tils/2021-01-12-awk-snippet-send-email-to-multiple-recipients-with-curl.md +++ /dev/null @@ -1,142 +0,0 @@ ---- - -title: 'Awk snippet: send email to multiple recipients with cURL' - -date: 2021-01-12 - -layout: post - -lang: en - -ref: awk-snippet-send-email-to-multiple-recipients-with-curl - ---- - -As I experiment with [Neomutt][neomutt], I wanted to keep being able to enqueue emails for sending later like my previous setup, so that I didn't rely on having an internet connection. - -My requirements for the `sendmail` command were: -1. store the email in a file, and send it later. -1. send from different addresses, using different SMTP servers; - -I couldn't find an MTA that could accomplish that, but I was able to quickly write a solution. - -The first part was the easiest: store the email in a file: - -```shell -# ~/.config/mutt/muttrc: -set sendmail=~/bin/enqueue-email.sh - -# ~/bin/enqueue-email.sh: -#!/bin/sh -eu - -cat - > "$HOME/mbsync/my-queued-emails/$(date -Is)" -``` - -Now that I had the email file store locally, I needed a program to send the email from the file, so that I could create a cronjob like: - -```shell -for f in ~/mbsync/my-queued-emails/*; do - ~/bin/dispatch-email.sh "$f" && rm "$f" -done -``` - -The `dispatch-email.sh` would have to look at the `From: ` header and decide which SMTP server to use. -As I [found out][curl-email] that [curl][curl] supports SMTP and is able to send emails, this is what I ended up with: - -```shell -#!/bin/sh -eu - -F="$1" - -rcpt="$(awk ' - match($0, /^(To|Cc|Bcc): (.*)$/, m) { - split(m[2], tos, ",") - for (i in tos) { - print "--mail-rcpt " tos[i] - } - } -' "$F")" - -if grep -qE '^From: .*<addr@server1\.org>$' "$F"; then - curl \ - -s \ - --url smtp://smtp.server1.org:587 \ - --ssl-reqd \ - --mail-from addr@server1.org \ - $rcpt \ - --user 'addr@server1.org:my-long-and-secure-passphrase' \ - --upload-file "$F" -elif grep -qE '^From: .*<addr@server2\.org>$' "$F"; then - curl \ - -s \ - --url smtp://smtp.server2.org:587 \ - --ssl-reqd \ - --mail-from addr@server2.org \ - $rcpt \ - --user 'addr@server2.org:my-long-and-secure-passphrase' \ - --upload-file "$F" -else - echo 'Bad "From: " address' - exit 1 -fi -``` - -Most of curl flags used are self-explanatory, except for `$rcpt`. - -curl connects to the SMTP server, but doesn't set the recipient address by looking at the message. -My solution was to generate the curl flags, store them in `$rcpt` and use it unquoted to leverage shell word splitting. - -To me, the most interesting part was building the `$rcpt` flags. -My first instinct was to try grep, but it couldn't print only matches in a regex. -As I started to turn towards sed, I envisioned needing something else to loop over the sed output, and I then moved to Awk. - -In the short Awk snippet, 3 things were new to me: the `match(...)`, `split(...)` and `for () {}`. -The only other function I have ever used was `gsub(...)`, but these new ones felt similar enough that I could almost guess their behaviour and arguments. -`match(...)` stores the matches of a regex on the given array positionally, and `split(...)` stores the chunks in the given array. - -I even did it incrementally: - -```shell -$ H='To: to@example.com, to2@example.com\nCc: cc@example.com, cc2@example.com\nBcc: bcc@example.com,bcc2@example.com\n' -$ printf "$H" | awk '/^To: .*$/ { print $0 }' -To: to@example.com, to2@example.com -$ printf "$H" | awk 'match($0, /^To: (.*)$/, m) { print m }' -awk: ligne de commande:1: (FILENAME=- FNR=1) fatal : tentative d'utilisation du tableau « m » dans un contexte scalaire -$ printf "$H" | awk 'match($0, /^To: (.*)$/, m) { print m[0] }' -To: to@example.com, to2@example.com -$ printf "$H" | awk 'match($0, /^To: (.*)$/, m) { print m[1] }' -to@example.com, to2@example.com -$ printf "$H" | awk 'match($0, /^To: (.*)$/, m) { split(m[1], tos, " "); print tos }' -awk: ligne de commande:1: (FILENAME=- FNR=1) fatal : tentative d'utilisation du tableau « tos » dans un contexte scalaire -$ printf "$H" | awk 'match($0, /^To: (.*)$/, m) { split(m[1], tos, " "); print tos[0] }' - -$ printf "$H" | awk 'match($0, /^To: (.*)$/, m) { split(m[1], tos, " "); print tos[1] }' -to@example.com, -$ printf "$H" | awk 'match($0, /^To: (.*)$/, m) { split(m[1], tos, " "); print tos[2] }' -to2@example.com -$ printf "$H" | awk 'match($0, /^To: (.*)$/, m) { split(m[1], tos, " "); print tos[3] }' - -``` - -(This isn't the verbatim interactive session, but a cleaned version to make it more readable.) - -At this point, I realized I needed a for loop over the `tos` array, and I moved the Awk snippet into the `~/bin/dispatch-email.sh`. -I liked the final thing: - -```awk -match($0, /^(To|Cc|Bcc): (.*)$/, m) { - split(m[2], tos, ",") - for (i in tos) { - print "--mail-rcpt " tos[i] - } -} -``` - -As I learn more about Awk, I feel that it is too undervalued, as many people turn to Perl or other programming languages when Awk suffices. -The advantage is pretty clear: writing programs that run on any POSIX system, without extra dependencies required. - -Coding to the standards is underrated. - -[neomutt]: https://neomutt.org/ -[curl-email]: https://blog.edmdesigner.com/send-email-from-linux-command-line/ -[curl]: https://curl.se/ |