Is it possible to stop `powershell` wrapping output in ANSI sequences?

• You mention powershell (powershell.exe), i.e. the CLI of Windows PowerShell.

• Windows PowerShell (unlike PowerShell (Core) 7+, see below) itself does not use coloring / formatting based on VT / ANSI escape sequences.

• The implication is that third-party code is producing the VT sequences in your case, so you must deactivate (or reconfigure) it to avoid such sequences in the output.

  • A prime candidate is a custom prompt function; such functions often involve coloring for a better command-line experience.

  • In programmatic use of powershell.exe, however, you would only see what the prompt function prints if you feed PowerShell commands to the CLI's stdin, accompanied by passing argument -File - to the CLI (to instruct it to read commands from stdin) or by default.

  • To exclude the prompt-function output from the output altogether, use -Command -, as discussed in the answer to your previous question.

  • If you do want it, but want to use the default prompt string, suppress $PROFILE loading with the -NoProfile parameter, which is generally preferable in programmatic processing.

Controlling use of colored output (VT / ANSI escape sequences) in PowerShell (Core) 7.2+

In PowerShell (Core) 7+ (pwsh.exe) - but not in Windows PowerShell (powershell.exe) - PowerShell itself situationally uses VT (ANSI) escape sequence to produce formatted/colored output, such as in the output of Select-String and, in v7.2+, in formatted output in general (column headers in tabular output / property names in list output).

• In PowerShell 7.2+ you can categorically suppress these as follows:

  • Note: Categorically disabling VT (ANSI) sequences is generally not necessary, because PowerShell automatically suppresses them when output is not sent to the host (display); that is, $PSStyle.OutputRendering defaults to Host^[1].

    • This amounts to the same behavior that may Unix utilities (sensibly) exhibit: coloring is by default only applied when printing to the display (terminal), not when piping to another command or redirecting to a file.

  • From outside PowerShell, before launching it:

    • By defining the NO_COLOR environment variable, with any value, such as 1.

      • This causes PowerShell to set $PSStyle.OutputRendering to PlainText on startup, which instructs PowerShell not to use VT / ANSI escape sequences.

      • A growing number of external programs also respect this env. variable - see no-color.org

    • Alternatively, by setting the TERM environment variable to xtermm / xterm-mono:

      • Note that value dumb, at least as of PowerShell Core 7.2.0-preview.9 (the most recent version as of this writing), doesn't work: while it does cause $host.UI.SupportsVirtualTerminal to then reflect $false, as documented, $PSStyle.OutputRendering remains at its default, Host, and actual formatted output (such as from Get-Item /) still uses colors.
      • However, setting TERM may be more effective than NO_COLOR in getting external programs not to emit VT sequences - ultimately, there's no guarantee however.
      • That said, modifying TERM, especially setting it to value dumb, is best avoided in general, because external programs (on Unix-like platforms) may rely on the TERM variable for inferring (also non-color-related) capabilities of the hosting terminal application (which setting the variable to dumb takes away altogether and - at least hypothetically - value xtermm / xterm-mono may misrepresent the true fundamental terminal type).

  • From inside PowerShell:

    • With $PSStyle.OutputRendering = 'PlainText'
      • Note that this alone - unlike the environment variables discussed above - does not affect the behavior of external programs.

Note that third-party PowerShell code that uses VT sequences, especially if it predates PowerShell (Core) 7+, may not respect any of the standard mechanisms described above for disabling them (though may conceivably offer a custom mechanism).

^{[1] This applies since v7.2.0-preview.9, where Host was made the default and the previous default, Automatic, was removed altogether.}

You can disable ANSI output rendering by setting the environment variable TERM to dumb:

SetEnvironmentVariable(TEXT("TERM"), TEXT("dumb"));
// proceed with your call to CreateProcess