F# API

function libtmux-fsharp latest

Selection.exactlyOne

Namespace L.FSharp LibTmux.FSharp

Returns the sole match, examining at most two elements.

Source and package

Module: LibTmux.FSharp
Declared in: Selection
Package: LibTmux.FSharp
Source: src/LibTmux.FSharp/Library.fsi

F# value signatures Declares the name and type of a value or function in a signature. Language documentation exactlyOne: source: seq<'T> -> Result<'T, CardinalityError>

function [source] ¶

Description#

Disposes the enumerator on success, multiple matches or failure.

Examples#

Select one session without using exceptions for ordinary cardinality outcomes. Match Ok, Error NoMatches and Error MultipleMatches explicitly. Use Linux or macOS with Git, tmux 3.2a or newer, .NET SDK 10.0.303, and the .NET 8 and 10 runtimes. In an empty directory, fetch the documented library revision:

$ git clone https://github.com/libtmux/libtmux-dotnet.git libtmux-source && \
  git -C libtmux-source checkout --detach cf34b255c896d19a97e7d7fabea58609c916012d

Save this complete consumer setup as global.json: View source

{
  "sdk": {
    "version": "10.0.303",
    "rollForward": "disable",
    "allowPrerelease": false
  },
  "test": {
    "runner": "Microsoft.Testing.Platform"
  }
}

Save this complete consumer setup as NuGet.config: View source

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <clear />
    <add key="libtmux-source" value="libtmux-source/artifacts/api-example-packages" />
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
  </packageSources>
  <packageSourceMapping>
    <clear />
    <packageSource key="libtmux-source">
      <package pattern="LibTmux" />
      <package pattern="LibTmux.*" />
    </packageSource>
    <packageSource key="nuget.org">
      <package pattern="*" />
    </packageSource>
  </packageSourceMapping>
</configuration>

Save this complete consumer setup as Example.fsproj: View source

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFrameworks>net8.0;net10.0</TargetFrameworks>
    <LangVersion>10.0</LangVersion>
    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
    <DisableImplicitFSharpCoreReference>true</DisableImplicitFSharpCoreReference>
    <DisableImplicitLibraryPacksFolder>true</DisableImplicitLibraryPacksFolder>
  </PropertyGroup>
  <ItemGroup>
    <Compile Include="Program.fs" />
    <PackageReference Include="FSharp.Core" Version="[10.1.303]" />
    <PackageReference Include="LibTmux.FSharp" Version="[0.0.0-alpha.20]" />
  </ItemGroup>
</Project>

Save this complete program as Program.fs. It creates a private server with LibTmux.Server.CreateOwnedAsync; use! disposes owned scopes after success, cancellation or failure. The F# facade has no separate server constructor. View source

open System
open System.Threading
open LibTmux
open LibTmux.FSharp

let runAsync () =
    task {
        use deadline = new CancellationTokenSource(TimeSpan.FromSeconds 10.)
        let token = deadline.Token

        let options =
            ServerConnectionOptions(
                SocketName = "fsharp-selection-" + Guid.NewGuid().ToString("N"),
                ConfigurationFile = "/dev/null"
            )

        use! owned = options |> Server.createOwned token

        use! _demo =
            owned.Value.CreateOwnedSessionAsync(NewSessionRequest(Name = "demo", Command = "/bin/cat"), token)

        use! _worker =
            owned.Value.CreateOwnedSessionAsync(NewSessionRequest(Name = "worker", Command = "/bin/cat"), token)

        let server = owned.Value
        let! sessions = server |> Server.sessions |> Query.list token

        // Exactly one match is Ok; none and several are distinct errors.
        let describe (result: Result<LibTmux.Session, CardinalityError>) =
            match result with
            | Ok session -> "Ok " + session.Name
            | Error NoMatches -> "Error NoMatches"
            | Error MultipleMatches -> "Error MultipleMatches"

        let named name =
            sessions |> Seq.filter (fun session -> session.Name = name)

        printfn "Sessions named demo: %s" (named "demo" |> Selection.exactlyOne |> describe)
        printfn "Sessions named missing: %s" (named "missing" |> Selection.exactlyOne |> describe)
        printfn "Every session: %s" (sessions |> Selection.exactlyOne |> describe)
    }

runAsync().GetAwaiter().GetResult()

Build the exact source packages and the saved consumer, then run both supported frameworks. The local package feed prevents an unrelated published package from satisfying the restore. Each program checks its result and exits unsuccessfully after an unhandled error:

$ export NUGET_PACKAGES="$PWD/packages" && \
  dotnet restore libtmux-source/src/LibTmux.FSharp/LibTmux.FSharp.fsproj --locked-mode && \
  dotnet pack libtmux-source/src/LibTmux/LibTmux.csproj \
    --configuration Release --no-restore -p:ContinuousIntegrationBuild=true \
    --output "$PWD/libtmux-source/artifacts/api-example-packages" && \
  dotnet pack libtmux-source/src/LibTmux.FSharp/LibTmux.FSharp.fsproj \
    --configuration Release --no-restore -p:ContinuousIntegrationBuild=true \
    --output "$PWD/libtmux-source/artifacts/api-example-packages" && \
  dotnet restore Example.fsproj --configfile NuGet.config && \
  dotnet build Example.fsproj --configuration Release --no-restore --warnaserror && \
  export LIBTMUX_TMUX="$(command -v tmux)" && \
  export TMUX_TMPDIR=/tmp/libtmux-dotnet-dev && \
  mkdir -p "$TMUX_TMPDIR" && \
  unset TMUX TMUX_PANE && \
  dotnet bin/Release/net8.0/Example.dll && \
  dotnet bin/Release/net10.0/Example.dll

Expected program output from each framework:

Sessions named demo: Ok demo
Sessions named missing: Error NoMatches
Every session: Error MultipleMatches

Parameters

source ( seq<'T> )

Discussed in Filtering and queries · .NET interoperation , Quick start

Scripting & web

Compiled & native

JVM

.NET

tmux

Selection.exactlyOne

Description#

Examples#

Description#

Examples#

Related types#