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--help or -h is used for help. We do not reserve the bare word "help", which
for example the ip command does. Reserving a bare word like help quickly
becomes cumbersome to handle in the code. It might be simple to handle
when it's passed early in the command chain like "ip addr help". But when
the user tries to pass "help" further down this requires manual checks and
special treatment. For example, at the time of writing this tool, it's
possible to create a vlan named "help" with the ip tool, but it's impossible
to remove it, the command just shows help. This is an effect of treating
bare words specially.
Help texts are not dynamically generated. That is, we do not pass datastructures
like command list or option lists and print them dynamically. This is
intentional. There is always that exception and when it comes to help texts
these exceptions are normally neglected at the expence of usability.
All options are key-values. There are both drawbacks and benefits to this.
The main drawback is that it becomes more to write for the user and
information might seem redundant. The main benefits is scalability and code
simplification. Consistency is important.
Consider this.
1. tipc link set priority PRIO link LINK
2. tipc link set LINK priority PRIO
Link might seem redundant in (1). However, if the command should live for many
years and be able to evolve example (2) limits the set command to only work on a
single link with no ability to extend. As an example, lets say we introduce
grouping on the kernel side.
1. tipc link set priority PRIO group GROUP
2. tipc link set ??? priority PRIO group GROUP
2. breaks, we can't extend the command to cover a group.
Commands are single words. As an example, all words in "tipc link list" are
commands. Options are key-values that can be given in any order. In
"tipc link set priority PRIO link LINK" "tipc link set" are commands while
priority and link are options. Meaning that they can be given like
"tipc link set link LINK priority PRIO".
Abbreviation matching works for both command and options. Meaning that
"tipc link set priority PRIO link LINK" could be given as
"tipc l s p PRIO l LINK" and "tipc link list" as "tipc l l".
The tool strives to avoid allocating memory on the heap. Most (if not all)
memory allocations are on the stack.
The tool could throw exit() deep down in functions but doing so always seems
to limit the program in the long run. So we output the error and return an
appropriate error code upon failure.