Read a file lazily through the .NET line iterator.
PowerShell: ReadLines avoids creating one string containing the entire file.
$ErrorActionPreference = 'Stop'
Set-StrictMode -Version Latest
foreach ($line in [IO.File]::ReadLines('lines.txt')) { $line.ToUpperInvariant() }Expected output EXAMPLE
ONE TWO
Details
Requires PowerShell 7. Save as snippet.ps1 and run pwsh -NoProfile -File snippet.ps1. Tested on Linux; these examples use portable paths and cmdlets. ReadLines avoids creating one string containing the entire file.
Tested on Ubuntu 24.04.5 LTS · · PowerShell 7.6.6 · powershell 7.6.6-1.deb
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Snippet process uid 65534 with a read-only root filesystem and temporary working files. Networking disabled. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged process) / C.UTF-8
- Interpreter invocation
pwsh -NoLogo -NoProfile -NonInteractive -File snippet.ps1- Container image ID
sha256:ec91410a8f6ec3e985830b5e3a0560306d36f8c1c5ccd91a6699abe707123fa3- Code SHA-256
bf9cb7b27a7ac7ae95c26b8d04f4b6c64bb124e80f7700856cb64b328319b39c- Dependencies
- powershell 7.6.6-1.deb
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
printf 'one\ntwo\n' > lines.txt
Observed standard output
ONE TWO
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.