---
name: "fddist"
section: "1m"
platform: "macos"
package: "dtrace"
version: "413"
release: "macOS 26.5"
platforms: ["macos"]
url: "https://new.carta.tech/fddist"
---

# fddist(1m)

file descriptor usage distributions. Uses DTrace.

## NAME

fddist - file descriptor usage distributions. Uses DTrace.

## SYNOPSIS

**fddist \[-r\|-w\]**

## DESCRIPTION

This prints distributions for read and write events by file descriptor, by process. This can be used to determine which file descriptor a process is doing the most I/O with.

Since this uses DTrace, only users with root privileges can run this command.

## OPTIONS

- \-r

  reads only

- \-w

  writes only

## EXAMPLES

- Sample both read and write activity,

  \#  **fddist**

- Sample reads only,

  \# **fddist** -r

## FIELDS

- EXEC

  process name

- PID

  process ID

- value

  file descriptor

- count

  number of events

## BASED ON

/usr/demo/dtrace/lquantize.d

## DOCUMENTATION

DTrace Guide "Aggregations" chapter (docs.sun.com)

See the DTraceToolkit for further documentation under the  Docs directory. The DTraceToolkit docs may include full worked examples with verbose descriptions explaining the output.

## EXIT

fddist will sample until Ctrl-C is hit.

## SEE ALSO

dtrace(1M)