F# API

function libtmux-fsharp latest

Pane.capture

Namespace L.FSharp LibTmux.FSharp

Captures pane contents using the supplied core request.

Source and package

Module: LibTmux.FSharp
Declared in: Pane
Package: LibTmux.FSharp
Source: src/LibTmux.FSharp/Hierarchy.fsi
Other languages: Python Ruby Lua TypeScript Rust Go Java C#C++Swift Kotlin Scala

F# value signatures Declares the name and type of a value or function in a signature. Language documentation capture: cancellationToken: CancellationToken -> request: CapturePaneRequest -> pane: LibTmux.Pane -> Task<IReadOnlyList<string>>

function [source] ¶

Examples#

Type a shell command literally, press the named Enter key, and wait for its private completion signal before capturing output. Timeout and command failures escape the program after scoped cleanup; cancellation does not undo dispatched input. 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 quoteShell (value: string) = "'" + value.Replace("'", "'\\''") + "'"

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

        let socketName = "fsharp-capture-" + Guid.NewGuid().ToString("N")

        let options =
            ServerConnectionOptions(SocketName = socketName, ConfigurationFile = "/dev/null")

        use! owned = options |> Server.createOwned token

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

        let server = owned.Value
        let! panes = server |> Server.panes |> Query.list token
        let pane = panes |> Seq.exactlyOne
        let channel = "capture-" + Guid.NewGuid().ToString("N")
        use wait = server.OpenWaitChannel(channel)
        let marker = "api capture ready"

        let command =
            sprintf
                "printf '%%s\\n' %s; tmux -L %s wait-for -S %s"
                (quoteShell marker)
                (quoteShell socketName)
                (quoteShell channel)

        do! pane |> Pane.sendText token command

        do! pane |> Pane.pressKey token "Enter"
        let! ready = wait.WaitAsync(TimeSpan.FromSeconds 5., token)
        printfn "The shell signalled: %b" ready

        let! lines = pane |> Pane.capture token (CapturePaneRequest(JoinWrappedLines = true))

        // Joining wrapped lines keeps the terminal's padding after the output,
        // and only a whole line counts, so the echoed command cannot match.
        match lines |> Seq.map (fun line -> line.TrimEnd()) |> Seq.tryFind ((=) marker) with
        | Some line -> printfn "Captured line: %s" line
        | None -> printfn "Captured line: none"
    }

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:

The shell signalled: true
Captured line: api capture ready

Type a line and wait for what it prints, not for its echo. Wait for a condition over the whole screen, then run a command and read its exit status and output. 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>

// fsharp-snippet: SendWaitRead
open System
open System.Threading
open LibTmux
open LibTmux.FSharp

let runAsync () =
    task {
        use deadline = new CancellationTokenSource(TimeSpan.FromSeconds 20.)
        let token = deadline.Token

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

        use! owned = options |> Server.createOwned token

        let! session =
            owned.Value |> Server.newSession token (SessionSpec.running "work" "/bin/sh")

        let! pane = session |> Session.activePane token

        // Type a line and wait for what it prints. The screen before it and
        // the line's own echo do not count.
        let! ready =
            pane
            |> Pane.sendAndWait token (TimeSpan.FromSeconds 5.) "echo server ready" "server ready"

        // A condition sees every visible row each time the pane changes.
        do! pane |> Pane.sendLine token "seq 3"

        let! counted =
            pane
            |> Pane.waitUntil token (TimeSpan.FromSeconds 5.) (fun rows -> rows |> Seq.exists ((=) "3"))

        // Running a command waits for its exit status and returns its output.
        let! listing =
            pane |> Pane.run token (TimeSpan.FromSeconds 10.) "printf 'a\\nb\\n'; exit 4"

        let! screen = pane |> Pane.capture token (CapturePaneRequest())

        // One case for each way a wait can end; leaving one out draws a warning.
        let describe wait =
            match wait with
            | PaneWait.Found -> "found"
            | PaneWait.Printed -> "printed"
            | PaneWait.Stopped pattern -> "stopped by " + pattern
            | PaneWait.TimedOut -> "timed out"
            | PaneWait.Ended -> "the pane's program ended"

        printfn "ready: %s" (describe ready)
        printfn "counted: %s" (describe counted)

        match listing with
        | PaneRun.Exited status -> printfn "run: exit %d, output %A" status (List.ofSeq listing.Output)
        | PaneRun.Ended -> printfn "run: the shell exited first"
        | PaneRun.NotStarted -> printfn "run: the shell was not at a prompt"
        | PaneRun.TimedOut -> printfn "run: still running"

        printfn "screen shows the run: %b" (screen |> Seq.exists (fun row -> row = "a"))
    }

runAsync().GetAwaiter().GetResult()
// endfsharp-snippet

$ 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:

ready: found
counted: found
run: exit 4, output ["a"; "b"]
screen shows the run: true

Parameters

cancellationToken ( CancellationToken )
request ( CapturePaneRequest )
pane ( LibTmux.Pane )

tmux command capture-pane

Discussed in Capture pane output · Getting started , Querying and filtering

In other ports Read a pane’s visible contents

Python libtmux.Pane.capture_pane
Ruby LibTmux::Pane#capture
Lua libtmux.Pane:capture
TypeScript pane.Pane.capture
Rust pane.Pane.capture
Go tmux.Pane.Capture
Java io.github.libtmux.Pane.capture
C# LibTmux.Pane.CaptureAsync
C++ libtmux::Pane::capture
Swift Server.capture(_:includingHistory:)
Kotlin io.github.libtmux.kotlin.Pane.capture
Scala io.github.libtmux.scaladsl.Pane.capture

Scripting & web

Compiled & native

JVM

.NET

tmux

Pane.capture

Examples#