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Pipe Commands

Pipe Commands#

Some NeoMutt config options can run a shell command and use its output instead of a static value. You enable this by ending the value with a | (pipe) character.

This tutorial walks through the most common use case: generating your email signature dynamically.

Step 1 — A Static Signature#

The simplest signature setup points $signature at a plain text file:

set signature = "~/.signature"

The file ~/.signature might contain:

Regards,
Alice

Every outgoing email gets the same signature.

Step 2 — Make It Dynamic with a Pipe#

Suppose you want your signature to include today’s date, a quote of the day, or different content depending on the recipient. Instead of a static file, you can point $signature at a script — just add | at the end:

set signature = "~/.mutt/gen-sig.sh|"

NeoMutt will:

  1. Strip the trailing |

  2. Execute ~/.mutt/gen-sig.sh as a shell command

  3. Read its standard output as the signature text

Step 3 — Write the Script#

Create the script ~/.mutt/gen-sig.sh:

#!/bin/sh
echo "Regards,"
echo "Alice"
echo ""
echo "Sent on $(date '+%A, %d %B %Y')"

Make it executable:

$ chmod +x ~/.mutt/gen-sig.sh

Now every email will have a signature like:

Regards,
Alice

Sent on Monday, 07 April 2025

Step 4 — Test It#

You can verify your script works by running it directly:

$ ~/.mutt/gen-sig.sh
Regards,
Alice

Sent on Monday, 07 April 2025

Then compose a test message in NeoMutt and check that the signature appears correctly at the bottom of the message body.

How It Works#

NeoMutt supports the trailing pipe in two categories of config options:

Path options (like $signature)

The value is treated as a command. NeoMutt runs it and reads the full output as if it were a file.

Expando options (like $index_format, $status_format, and others)

After NeoMutt expands the format string, if the result ends with |, the expanded string is executed as a command and the first line of output replaces it.

See also