-k FILE (conditional operator)

true if the file or directory exists and has its sticky bit set.

-k is not included in POSIX.1-2017, but is provided by some implementations.

Quoting from man chmod:

The restricted deletion flag or sticky bit is a single bit, whose interpretation depends on the file type. For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp.

For regular files on some older systems, the bit saves the program’s text image on the swap device so it will load more quickly when run; this is called the sticky bit.

Links

• Bash manual
• POSIX specification of test

Examples

Different ways to test if the sticky bit of a file is set:

1 2 3 4

test -k ~/file.txt && echo "sticky bit set" [ -k ~/file.txt ] && echo "sticky bit set" # Bash [[ -k ~/file.txt ]] && echo "sticky bit set"

Set the sticky bit for a file

1	chmod u+t ~/file.txt