Guide to Unix/Commands/Devices

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fuser[edit]

fuser tells you what process is using an indicated filesystem object (ordinary file, device, etc.)

$ fuser /dev/dsp
/dev/dsp:             8369

lsof[edit]

lsof lists all open files,is more detailed than fuser.

Example:

$ lsof /dev/dsp
COMMAND  PID USER   FD   TYPE DEVICE SIZE NODE NAME
mplayer 8406 alex    7w   CHR   14,3       389 /dev/sound/dsp

Tips:

Using -i 4 option will report all programs currently using IPv4 network, it is useful for watching the programs accessing the network and Internet resources.

$ lsof -i 4
COMMAND    PID   USER   FD   TYPE DEVICE SIZE NODE NAME
btdownloa 2618 arky    3u  IPv4   9524       TCP *:6886 (LISTEN)
btdownloa 2618 arky    6u  IPv4   9544       TCP  dsl-KK-229.53.101.203.ttel.net:1539->cpc1-leed3-3-0-cust10.ldst.cable.ntl.com:59074 (ESTABLISHED)

fstat[edit]

fstat lists all open files.

The previous two commands (fuser and lsof) do not exist on all systems. The 4.3BSD-Tahoe system introduced the "fstat" command that is found on many *BSD systems. Unlike the previous two commands, it seems not to know the exact path of each file, but only what filesystem it is on?

Some options are:

 -p PROCESSID  show open files of this process
 -u USERNAME   show open files of this user

Examples: Lists every open file by every user, including root! Pipe it into a pager.

$ fstat | less

Get the process ID of the running Bourne shell and then list the files it opened.

$ echo $$
5283
$ fstat -p 5283
USER     CMD          PID   FD MOUNT      INUM MODE       R/W    DV|SZ
...

The init process always has ID of 1. List its open files. In this example it only opened one file somewhere on the / filesystem.

$ fstat -v -p 1
USER     CMD          PID   FD MOUNT      INUM MODE       R/W    DV|SZ
root     init           1   wd /             2 drwxr-xr-x   r      512

Reference: