Implement deletion of SysV IPC message queues

As usual also the readme and the man page are updated.

src/main.rs

@@ -25,6 +25,7 @@ enum PosixCommand {
 #[derive(Clap, Debug)]
 enum SysvCommand {
     Create(sysv::Create),
+    Unlink(sysv::Unlink),
 }
 
 #[derive(Clap, Debug)]
@@ -68,6 +69,7 @@ fn main() -> Result<()> {
         },
         Backend::Sysv(s) => match s {
             SysvCommand::Create(c) => c.run()?,
+            SysvCommand::Unlink(u) => u.run()?,
         },
     }
 

src/sysv.rs

@@ -1,3 +1,5 @@
 mod create;
+mod unlink;
 
 pub use create::Create;
+pub use unlink::Unlink;

src/sysv/unlink.rs

@@ -0,0 +1,35 @@
+use anyhow::Result;
+use clap::Clap;
+use log::info;
+
+/// Delete a message queue
+#[derive(Clap, Debug)]
+pub struct Unlink {
+    /// Id of the queue
+    #[clap(
+        long,
+        short,
+        required_unless_present_any = &["key"],
+        conflicts_with = "key"
+    )]
+    pub id: Option<i32>,
+    /// Key of the queue
+    #[clap(long, short, required_unless_present_any = &["id"], conflicts_with = "id")]
+    pub key: Option<i32>,
+}
+
+impl Unlink {
+    pub fn run(&self) -> Result<()> {
+        if let Some(id) = self.id {
+            sysvmq::unlink_id(id)?;
+
+            info!("Removed message queue with id: {}", id);
+        } else if let Some(key) = self.key {
+            sysvmq::unlink_key(key)?;
+
+            info!("Removed message queue key: {}", key);
+        }
+
+        Ok(())
+    }
+}