In the course of my career, I’ve periodically come across code like this in shell scripts:
TEMP_FILE=/tmp/tempfileOr sometimes, slightly more elegantly:
TEMPFILE=/tmp/tempfile.$$The problems with the first example are obvious, especially if it appears in many different scripts. The second is better. The “$$” means “my process ID”, who if whatever script had a process ID of 5309, the TEMPFILE variable would be set to /tmp/tempfile.5309. This makes collisions between scripts extremely unlikely, but is still suboptimal. What if there is a file called /tmp/tempfile.5309 and it’s owned by another user, or what if you don’t have permission to write to /tmp? It’d be better to find out immediately than many lines later when you try to write something. …
Source: Here Today, Gone When You Exit: Proper Tempfiles in Shell Scripts – LowEndBox
