Unix Tools

The shell has interacts with a set of Unix tools in /bin and so forth. However, in many cases, those tools have grown functionality that overlaps with shell.

Unix Tools ...

That Start Processes (in parallel)

• make and other build tools. make -j for parallel builds.
• xargs, -P for parallel execution, -I {} for substitution
  • Also GNU Parallel, which is mentioned in the bash manual
• find -exec and -exec +

That Have Expression Languages

Expression languages must be fully recursive to count here.

With no lexer:

• find -- -a -o ! ( )
• test -- -a -o ! ( )
• expr -- arithmetic, subsumed by $(())

Languages with lexers:

• awk

That Use Regexes

• grep, grep -E
• sed, sed --regexp-extended in GNU sed
• awk (extended only)
• expr
• find -regex
• bash itself

That Receive Code Snippets (Remote Evaluation)

• tar has a --sed option

That Have Printf-Style Formatting

See Appendix A: How to Quickly and Correctly* Generate a Git Log in HTML

• find -printf (arbitrary filenames)
• stat -c (arbitrary filenames)
• git log --pretty=format: (arbitrary descriptions)
• curl --write-out %{response_code} -- URLs can't have arbitrary characters?
• printf itself (coreutils)
• time (/usr/bin/time) -- mostly numbers
• date -- mostly numbers
• bash
  • the printf builtin
  • the time builtin and the TIMEFORMAT string -- mostly numbers
  • the prompt string: \h \W
• ps --format

With Tabular Output

• find / ls
• ps
• df (has -h and -H human-readable option, but no format string)

The Worst Offender

find starts processes (in parallel), it a recursive boolean expression language, it has regexes (and globs), and it has field substitution. It should be part of the shell!