Refactor commands to support different backends

Therefore also the `sysv` backend is intoduced to prepare for future
support. The man page and the readme are updated so far.

README.md

@@ -46,31 +46,38 @@ from `target/{debug,release}/mqrs` depending on which
 one you built.
 
 ## Using `mqrs`
-`mqrs` supports five commands: `create`, `info`, `list`, `unlink`,
+Depending on which backend you want to use there are different subsets
-`send` and `recv`. All commands do not have to be specified fully. If
+of subcommands. Following backends are supported:
-the command is clearly distinguishable from all the others, it does
+- `posix`: Uses POSIX message queues
-not have to be completed further.
+- `sysv`: Uses SysV IPC message queues
 
-### Create a message queue
+If a command is clearly distinguishable from all the others,
+it does not have to be completed further.
+
+### POSIX message queues
+The POSIX backend supports six commands: `create`, `info`, `list`,
+`unlink`, `send` and `recv`.
+
+#### Create a message queue
 Use the `create` command to create a new POSIX message queue. Following
 optional arguments are supported:
 - `-c`, `--capacity`: Maximum number of messages in the queue
 - `-p`, `--permissions`: Permissions (octal) to create the queue with
 - `-s`, `--msgsize`: Message size in bytes
 
-### Print information about a message queue
+#### Print information about a message queue
 Use the `info` command to print further information about a message
 queue.
 
-### List all message queues
+#### List all message queues
 Use the `list` command to print a list of all message
 queues. Following option argument is supported:
 - `-a`, `--all`: Print all available information
 
-### Delete a message queue
+#### Delete a message queue
 Use the `unlink` command to delete a message queue.
 
-### Send a message to a queue
+#### Send a message to a queue
 Use the `send` command to send a message to a message queue. Following
 optional arguments are supported:
 - `-n`, `--non-blocking`: Do not block
@@ -80,7 +87,7 @@ optional arguments are supported:
   default, priority >= 0 [default: 0]
 - `-o`, `--timeout <timeout>`: As for example in "5h 23min 42ms"
 
-### Receive a message from a queue
+#### Receive a message from a queue
 Use the `recv` command to receive one or more messages from a message
 queue. Following optional arguments are supported:
 - `-f`, `--follow`: Print messages as they are received
@@ -89,3 +96,6 @@ queue. Following optional arguments are supported:
 - `-d`, `--deadline <deadline>`: Deadline until messages are received
   (format: `%Y-%m-%d %H:%M:%S`)
 - `-o,` `--timeout <timeout>`: As for example in "5h 23min 42ms"
+
+### SysV IPC message queues
+The SysV IPC backend supports no commands yet.

mqrs.1

@@ -1,12 +1,34 @@
 .\" Manpage for mqrs
-.TH man 1 "27 June 2021" "0.1.1" "mqrs man page"
+.TH man 1 "7 July 2021" "0.1.1" "mqrs man page"
 .SH NAME
 mqrs \- Handle POSIX message queues
 .SH SYNOPSIS
 .B mqrs [\-h] [\-\-help] [\-v] [\-\-verbose] [\-V] [\-\-version] [SUBCOMMAND]
 .SH DESCRIPTION
 .B mqrs
-is a small cli program to handle POSIX message queues. Supported commands are
+is a small cli program to handle message queues. Depending on which
+backend you want to use there are different subsets of
+subcommands. Following backends are supported:
+.B posix\
+and
+.B sysv\
+.
+
+If a command is clearly distinguishable from all the others, it does
+not have to be completed further.
+.SH OPTIONS
+.TP 8
+.B \-h, \-\-help
+Prints help information
+.TP 8
+.B \-v, \-\-verbose
+Produce verbose output, multiple -v options increase the verbosity
+(max. 3)
+.TP 8
+.B \-V, \-\-version
+Prints version information
+.SH POSIX MESSAGE QUEUE SUBCOMMANDS
+The POSIX backend supports six commands:
 .B create\
 ,
 .B info\
@@ -19,21 +41,6 @@ is a small cli program to handle POSIX message queues. Supported commands are
 and
 .B recv
 .
-All commands do not have to be specified fully. If the command is
-clearly distinguishable from all the others, it is not needed to
-complete it further.
-.SH OPTIONS
-.TP 8
-.B \-h, \-\-help
-Prints help information
-.TP 8
-.B \-v, \-\-verbose
-Produce verbose output, multiple -v options increase the verbosity
-(max. 3)
-.TP 8
-.B \-V, \-\-version
-Prints version information
-.SH SUBCOMMANDS
 .SS create [FLAGS] [OPTIONS] \fI<QUEUE>\fP
 Create a new POSIX message queue.
 .TP 8
@@ -202,6 +209,8 @@ Prints help information
 .B \-v, \-\-verbose
 Produce verbose output
 .RE
+.SH SYSV IPC MESSAGE QUEUE SUBCOMMANDS
+The SysV IPC backend supports no commands yet.
 .SH SEE ALSO
 mq_overview(7)
 .SH BUGS

src/main.rs

@@ -4,7 +4,15 @@ use clap::{crate_authors, crate_version, AppSettings, Clap};
 mod posix;
 
 #[derive(Clap, Debug)]
-enum Command {
+enum Backend {
+    /// Handle POSIX message queues
+    Posix(PosixCommand),
+    /// Handle SysV message queues
+    Sysv(SysvCommand),
+}
+
+#[derive(Clap, Debug)]
+enum PosixCommand {
     Create(posix::Create),
     Info(posix::Info),
     List(posix::List),
@@ -13,6 +21,10 @@ enum Command {
     Recv(posix::Recv),
 }
 
+#[derive(Clap, Debug)]
+enum SysvCommand {
+}
+
 #[derive(Clap, Debug)]
 #[clap(
     version = crate_version!(),
@@ -25,8 +37,9 @@ struct Opts {
     /// Produce verbose output, multiple -v options increase the verbosity (max. 3)
     #[clap(short, long, global = true, parse(from_occurrences))]
     verbose: u32,
+    /// Backend to be used
     #[clap(subcommand)]
-    command: Command,
+    backend: Backend,
 }
 
 fn main() -> Result<()> {
@@ -42,13 +55,17 @@ fn main() -> Result<()> {
     ))
     .init();
 
-    match opts.command {
+    match opts.backend {
-        Command::Create(c) => c.run()?,
+        Backend::Posix(p) => match p {
-        Command::Info(i) => i.run()?,
+            PosixCommand::Create(c) => c.run()?,
-        Command::Unlink(u) => u.run()?,
+            PosixCommand::Info(i) => i.run()?,
-        Command::Send(s) => s.run()?,
+            PosixCommand::List(l) => l.run()?,
-        Command::Recv(r) => r.run()?,
+            PosixCommand::Unlink(u) => u.run()?,
-        Command::List(l) => l.run()?,
+            PosixCommand::Send(s) => s.run()?,
+            PosixCommand::Recv(r) => r.run()?,
+        },
+        Backend::Sysv(s) => match s {
+        },
     }
 
     Ok(())