Linux: cat with separators among files

vmtouch seems like a good tool for the job.

Highlights:

• query how much of a directory is cached
• query how much of a file is cached (also which pages, graphical representation)
• load file into cache
• remove file from cache
• lock files in cache
• run as daemon

vmtouch manual

EDIT: Usage as asked in the question is listed in example 5 on vmtouch Hompage

Example 5

Daemonise and lock all files in a directory into physical memory:

vmtouch -dl /var/www/htdocs/critical/

EDIT2: As noted in the comments, there is now a git repository available.

From diff man page:

If both from-file and to-file are directories, diff compares corresponding files in both directories, in alphabetical order; this comparison is not recursive unless the -r or --recursive option is given. diff never compares the actual contents of a directory as if it were a file. The file that is fully specified may not be standard input, because standard input is nameless and the notion of ‘‘file with the same name’’ does not apply.

So to compare directories: diff --brief -r dir1 dir2

To compare files side by side: diff --side-by-side file1 file2