On , I learnt ...

How temporary files are removed on MacOS

On MacOS, temporary files are stored in either /tmp/ or a per-user temporary folder specified by the $TMPDIR environment variable; this is normally a subfolder of /var/folders/.

Temporary files are periodically removed by the com.apple.periodic-daily launch daemon (specified in /System/Library/LaunchDaemons/com.apple.periodic-daily.plist). This runs the /usr/sbin/periodic shell script (via /usr/libexec/periodic-wrapper). This runs all scripts in /etc/periodic/daily/ including /etc/periodic/daily/110.clean-tmps which is responsible for removing old temporary files. The default configuration /etc/defaults/periodic.conf ensures any files in /tmp that haven’t been accessed for 3 days are deleted.

# /etc/defaults/periodic.conf

# 110.clean-tmps
daily_clean_tmps_enable="YES"      # Delete stuff daily
daily_clean_tmps_dirs="/tmp"       # Delete under here
daily_clean_tmps_days="3"          # If not accessed for

Output from this job is logged in /var/log/daily.out.

It’s hard to determine exactly how stale files in $TMPDIR are removed. The folder appears to be flushed when a machine reboots but I can’t tell if they are periodically removed as well.

This is accurate as of MacOS 10.15.7