The Linux Programming Interface

BPARSING COMMAND-LINE OPTIONS

A typical UNIX command line has the following form:

command [ options ] arguments

An option takes the form of a hyphen (-) followed by a unique character identifying the option and a possible argument for the option. An option that takes an argument may optionally be separated from that argument by white space. Multiple options can be grouped after a single hyphen, and the last option in the group may be one that takes an argument. According to these rules, the following commands are all equivalent:

$ grep -l -i -f patterns *.c$ grep -lif patterns *.c$ grep -lifpatterns *.c

In the above commands, the –l and –i options don’t have an argument, while the –f option takes the string patterns as its argument.

Since many ...