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

# opensnoop(1m)

snoop file opens as they occur. Uses DTrace.

## NAME

opensnoop - snoop file opens as they occur. Uses DTrace.

## SYNOPSIS

**opensnoop** \[-a\|-A\|-ceFghstvxZ\] \[-f pathname\] \[-n name\] \[-p PID\]

## DESCRIPTION

opensnoop tracks file opens. As a process issues a file open, details such as UID, PID and pathname are printed out.

The returned file descriptor is printed, a value of -1 indicates an error. This can be useful for troubleshooting to determine if applications are attempting to open files that do not exist.

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

## OPTIONS

- \-a

  print all data

- \-A

  dump all data, space delimited

- \-c

  print current working directory of process

- \-e

  print errno value

- \-F

  print the flags passed to open

- \-g

  print full command arguments

- \-s

  print start time, us

- \-t

  print user stack trace

- \-v

  print start time, string

- \-x

  only print failed opens

- \-Z

  print zonename

- \-f pathname

  file pathname to snoop

- \-n name

  process name to snoop

- \-p PID

  process ID to snoop

## EXAMPLES

- Default output, print file opens by process as they occur,

  \#  **opensnoop**

- Print human readable timestamps,

  \#  **opensnoop** -v

- See error codes,

  \# **opensnoop** -e

- Snoop this file only,

  \# **opensnoop** -f /etc/passwd

## FIELDS

- ZONE

  Zone name

- UID

  User ID

- PID

  Process ID

- PPID

  Parent Process ID

- FD

  File Descriptor (-1 is error)

- FLAGS

  Flags passed to open

- ERR

  errno value (see /usr/include/sys/errno.h)

- CWD

  current working directory of process

- PATH

  pathname for file open

- COMM

  command name for the process

- ARGS

  argument listing for the process

- TIME

  timestamp for the open event, us

- STRTIME

  timestamp for the open event, string

## DOCUMENTATION

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

opensnoop will run forever until Ctrl-C is hit.

## BUGS

occasionally the pathname for the file open cannot be read and the following error will be seen,

dtrace: error on enabled probe ID 6 (...): invalid address

this is normal behaviour.

## AUTHOR

Brendan Gregg \[Sydney, Australia\]

## SEE ALSO

dtrace(1M), [truss(1)](/truss/1.md)