Skip to content
fuck-powershell

escaping a quote ENDS the quoted span, so one JSON argument silently becomes several

args quoting · case

5.1misleading-erroragentscriptcifirst-partyrepro: verifiednative-argv-rebuild
Affectsnode, powershell 51, windows
Fails asINVALID JSON
Mechanismnative argv rebuild
Safe fixfile payload

Symptom

Section titled “Symptom”

You pass a JSON payload to a CLI as one argument. The tool answers invalid JSON — or worse, silently receives a different number of arguments than you passed. Every escaping trick you try fails a slightly different way, so it feels like the CLI is broken.

It isn’t. Escaping a double quote in PowerShell ends the quoted region, so the first space after it becomes an argument separator.

Repro

Section titled “Repro”

Probe that prints the child’s raw argv:

argv.mjs
const args = process.argv.slice(2);
console.log("argc=" + args.length);
args.forEach((a, i) => console.log(i + ": " + JSON.stringify(a)));
Terminal window
# A — single quotes: every double quote is eaten
node argv.mjs --attest '{"a":"b"}'
# argc=2 / 1: "{a:b}"                      <- not JSON anymore


# B — backslash-escaped, no space in the value: survives
node argv.mjs --attest '{\"a\":\"b\"}'
# argc=2 / 1: "{\"a\":\"b\"}"                 <- looks like the fix!


# C — same escaping, ONE space in the value: splits
node argv.mjs --attest '{\"a\":\"b c\"}'
# argc=3 / 1: "{\"a\":\"b"  2: "c\"}"          <- one arg became two


# D — control: plain quoted string with spaces is fine
node argv.mjs "b c d"
# argc=1 / 0: "b c d"

B is the trap. It works, you ship it, and it breaks the first time a value contains a space — which for a --message, --body or --did field is immediately.

Every “obvious” workaround also fails

Section titled “Every “obvious” workaround also fails”
Terminal window
$j = '{"a":"b c"}'; node argv.mjs --attest $j            # 1: "{a:b c}"   quotes stripped
$j = @'
{"a":"b c"}
'@; node argv.mjs --attest $j                            # 1: "{a:b c}"   here-string does not help
$j = @{a="b c"} | ConvertTo-Json -Compress
node argv.mjs --attest $j                                # quotes stripped too
node argv.mjs --% --attest {"a":"b c"}                   # argc=3, and it swallowed "2>&1" as an argument

Building valid JSON in PowerShell does not help, because the damage happens when the argument vector is rebuilt for the native process, after your variable is correct.

--% deserves its own warning: it stops parsing for everything that follows, so your redirection operators become literal arguments.

Cause

Section titled “Cause”

PowerShell rebuilds a command line for native processes and re-quotes by heuristic. A backslash-escaped \" reaches that rebuilder as a real quote character, which closes the quoted span; the remainder of the value is then treated as unquoted text and split on whitespace. Single quotes take the opposite path — the quotes never survive at all.

Workaround

Section titled “Workaround”

Use PowerShell’s own doubling escape inside single quotes:

Terminal window
$j = '{""from"":""P"",""did"":""two words here""}'
node -e "console.log(JSON.parse(process.argv[1]))" $j
# -> { from: 'P', did: 'two words here' }     parses correctly

Better, avoid argv entirely for structured payloads:

Terminal window
# file transport
'{"a":"b c"}' | Set-Content -Encoding utf8 $env:TEMP\p.json
mytool --attest-file $env:TEMP\p.json


# base64 transport, when the tool supports it
$b = [Convert]::ToBase64String([Text.Encoding]::UTF8.GetBytes($j))
mytool --attest-b64 $b

If you are designing the CLI: ship a --x-file flag. On Windows it is not a convenience, it is the only reliable channel for anything containing a space and a quote.

oss-native-arg-quoting documents that quotes get stripped and empty args vanish. This case is the follow-on that bites after you read that one and start escaping: the escape appears to work, and then silently changes your argument count the moment a value contains a space. The doubled-quote-inside-single-quotes workaround is not recorded anywhere in the archive.

Environment

Section titled “Environment”

$PSVersionTable: 5.1.26100.7705, Edition Desktop, Windows 11, Node 22.14.

Refs

Section titled “Refs”