How do I create temporary files and directories in a secure way on linux?

mountaing

Many know of putting the process ID at the end of the file /tmp/mylog.$$, which can be done as long as there is nothing sensitive in the file. The $$ just puts your shell process id at the end of the file.
The file name is created with these permissions; anyone can read it.

ls -l /tmp/mylog.5929
-rw-rw-r-- 1 trainer trainer 0 Nov 13 11:18 mylog.5929

A better way is to always use mktemp in scripts to make the file name difficult for anyone to guess.

Create a temporary file with 10 random characters.

$ mktemp /tmp/mylog.XXXXXXXXXX
/tmp/mylog.LlIu9B0PPw

Notice the file permissions are a lot more secure.

$ ls -l /tmp/mylog.LlIu9B0PPw
-rw------- 1 trainer trainer 0 Nov 13 11:15 /tmp/mylog.LlIu9B0PPw

The same can be done for directories. Assuming TMPDIR is set to /tmp.

$ mktemp -d -t my_logfiles.XXXXXXXXXX
/tmp/my_logfiles.l2DPRJuGne

$ ls -ld /tmp/my_logfiles.l2DPRJuGne
drwx------ 2 trainer trainer 2 Nov 13 11:24 /tmp/my_logfiles.l2DPRJuGne