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+title = "Creating a Temporary File Hoster"
+date = 2022-04-27
+draft = false
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+For the past couple years, whenever I wanted to upload a file, I would
+curl the file to [lainsafe](https://git.qorg11.net/lainsafe.git/), [i/u.kalli.st](https://gt.kalli.st/kallist/uploader), and recently [ttm.sh](https://tildegit.org/tildeverse/ttm.sh).
+
+Since I want to selfhost, I thought i can just use either of what those
+three used. Earlier today though, I realized I could just copy the
+file(s) I want to upload via rsync/scp to a public directory that gets
+served by an httpd or gopherd.
+
+From what I understand, the previous file hosters had a program running
+that read the file that the user uploads to them, does some renaming,
+and writes that to a directory that is served. After some time, that
+file is deleted. The first part can be handled via rsync/scp like
+mentioned previously. For automatic deletion, I recently saw in find's
+man page that it can list that haven't been modified via the -mtime
+flag, so that can be used with a cron job.
+
+But while thinking of this idea, I got stumped by how to print back the
+url to this file that is uploaded since printing the filename as is
+appended to its baseurl, there could be spaces and other invalid
+unescaped characters which programs trying to download it may not like.
+
+I thought I could just create a separate program for this. However,
+doing this seemed more complicated than just copying the file to the
+server. So, with the help of awk and some StackExchanging, I've been
+able to do it.
+
+`upfile.sh`:
+```sh
+#!/bin/sh
+urlencode() {
+     awk '
+BEGIN { for (i = 1; i < 256; i++) hex[sprintf("%c", i)] = sprintf("%%%02X", i) }
+{
+     for (i = 1; i <= length($0); i++) {
+             c = substr($0, i, 1)
+             printf("%s", c ~ /^[-._~0-9a-zA-Z]$/ ? c : hex[c])
+     }
+     printf "\n"
+}
+'
+}
+
+FILE="$1"
+SERVER="REPLACEME"
+BASEURL="https://u.$SERVER"
+
+[ -z "$1" ] && exit 1
+
+scp "$FILE" "$SERVER":files/ || exit 1
+printf "%s/" "$BASEURL"
+basename "$FILE" | urlencode
+```
+
+Then to purge these files after they become too old (e.g. 3 days), you
+can put something like this in a cron job to run daily (replace file
+directory):
+
+```
+0 0 * * * find /path/to/dir/ -mtime +3 -exec rm {} \;
+```
+
+You can also put this command in /etc/daily.local or /etc/cron/daily,
+or whatever file your root crontab's @daily runs (if there is one).
+
+And that's it! The only difficult part that I experienced was encoding
+the name of the file and originally did that in C. However, having a
+mixed C and shell program just for file uploading didn't sit right with
+me. It seems like whenever you're in doubt, you can rely on awk huh.