Hide

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again.

Delete that bloated snippets file you've been using and share your personal repository with the world. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

If you have a new feature suggestion or find a bug, please get in touch via http://commandlinefu.uservoice.com/

Get involved!

You can sign-in using OpenID credentials, or register a traditional username and password.

OpenID
or
Sign in Register

First-time OpenID users will be automatically assigned a username which can be changed after signing in.

Hide

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for:

Hide

News

2011-03-12 - Confoo 2011 presentation
Slides are available from the commandlinefu presentation at Confoo 2011: http://presentations.codeinthehole.com/confoo2011/
2011-01-04 - Moderation now required for new commands
To try and put and end to the spamming, new commands require moderation before they will appear on the site.
2010-12-27 - Apologies for not banning the trolls sooner
Have been away from the interwebs over Christmas. Will be more vigilant henceforth.
2010-09-24 - OAuth and pagination problems fixed
Apologies for the delay in getting Twitter's OAuth supported. Annoying pagination gremlin also fixed.
Hide

Tags

Hide

Functions

Hide

Credits

Site by David Winterbottom (user root).

Commands by mhs from sorted by
Terminal - Commands by mhs - 21 results
[ ! -d /squashed/usr ] && mkdir -p /squashed/usr/{ro,rw} ; mksquashfs /usr /squashed/usr/usr.sfs.new -b 65536 ; mv /squashed/usr/usr.sfs.new /squashed/usr/usr.sfs ; reboot
2014-05-10 06:01:06
User: mhs
Functions: mkdir mv
Tags: performance ssd squashfs
4
Up
Down
Performance tip: compress /usr/

Periodically run the one-liner above if/when there are significant changes to the files in /usr/

= Before rebooting, add following to /etc/fstab : =

/squashed/usr/usr.sfs /squashed/usr/ro squashfs loop,ro 0 0 usr /usr aufs udba=reval,br:/squashed/usr/rw:/squashed/usr/ro 0 0

No need to delete original /usr/ ! (unless you don't care about recovery). Also AuFS does not work with XFS

Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
sdparm -s SCT=36000 --save /dev/sdb
2013-04-19 13:26:18
User: mhs
Tags: sdparm
2
Up
Down
Increase SCT of external USB disk enclosure to one hour.

So I had this 2TB Seagate external disk/USB enclosure which by default would spin-down its internal drive (it enters a standby mode) after four minutes of inactivity.. Spinning-up the inactive drive was an annoying delay when accessing files and also it severely interfered with NFS.. SCT stands for "Standby Condition Timer".

To completely disable SCT:

sdparm --clear STANDBY -6 /dev/sdb

To return to original (default) SCT settings:

sdparm -D -p 0x1a -6 /dev/sdb

To verify the settings (before and after):

sdparm -a /dev/sdb

No need for vendor-provided MSWIN tools, etc.

Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
prlimit --cpu=10 sort -u hugefile
2013-02-27 15:59:11
User: mhs
Functions: sort
Tags: cpu util-linux
4
Up
Down
Limit the cpu usage of a process

Similar to `cpulimit`, although `prlimit` can be found shipped with recent util-linux.

Example: limit CPU consumption to 10% for a math problem which ordinarily takes up 100% CPU:

Before:

bc -l <(echo "1234123412341234^12341234")

See the difference `prlimit` makes:

prlimit --cpu=10 bc -l <(echo "1234123412341234^12341234")

To actually monitor the CPU usage, use `top`, `sar`, etc.. or:

pidstat -C 'bc' -hur -p ALL 1
Comments (3) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
soffice --headless -convert-to odt:"writer8" somefile.docx
2012-12-27 15:08:38
User: mhs
Tags: convert libreoffice soffice
14
Up
Down
Commandline document conversion with Libreoffice

In this example, the docx gets converted to Open Document .odt format.

For other formats, you'll need to specify the correct filter (Hint: see "Comments" link below for a nice list).

Comments (1) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
adb pull /dev/graphics/fb0 /dev/stdout | ffmpeg -vframes 1 -vcodec rawvideo -f rawvideo -pix_fmt rgb32 -s 480x800 -i pipe:0 -f image2 -vcodec png screenshot.png
2012-12-26 13:21:18
User: mhs
Tags: screenshot adb android
8
Up
Down
Android PNG screenshot

Works with *rooted* Android devices. 400x800 are the screen dimensions of a typical handheld smartphone.

Comments (1) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
adb pull /data/data/com.android.providers.contacts/databases/contacts2.db ; sqlite3 -batch <<EOF contacts2.db <CR> .header on <CR> .mode tabs <CR> select * from data; <CR> EOF
2012-12-26 11:35:23
User: mhs
Functions: tabs
Tags: contacts adb android sms sqlite3
2
Up
Down
Dump android contacts, sms

Crude, but works. Note for security, /data/ will be inaccessible unless your device has been *rooted*.

On the other hand, if a device has been rooted, its data is now wide open to anyone with a USB cable and the above "one-liner".

`adb` is one of the platform tools in the android SDK.

To get SMS messages:

adb pull /data/data/com.android.providers.telephony/databases/mmssms.db ; sqlite3 -batch <<EOF contacts2.db <CR> .header on <CR> .mode tabs <CR> select * from sms; <CR> EOF
Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
http_proxy=http://127.0.0.1:3128 wget --http-user='domain\account' --http-password='###' -p -r -l 8 --no-remove-listing -P . 'http://sp.corp.com/teams/Team/Shared%20Documents/Forms/AllItems.aspx?RootFolder=%2fteams%2fTeam%2fShared%20Documents%2fFolder'
2012-12-26 09:03:55
User: mhs
Functions: wget
Tags: wget sharepoint cntlm
1
Up
Down
wget multiple files (or mirror) from NTLM-protected Sharepoint

If you have to deal with MS Sharepoint which is (rarely, let's hope) used in e.g. certain corporate environments).

This uses Cntlm.

For single files, just use cURL -- its NTLM authentication works quite well.

# /etc/cntlm.conf:

# Username account

# Domain domain

# Password ############

# Proxy 10.20.30.40 (IP of the sharepoint site)

# NoProxy *

# Listen 3128

Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
socat unix-connect:/tmp/socket stdio,echo=0,raw
2012-12-19 07:58:09
User: mhs
Tags: serial console socat vmware
1
Up
Down
Serial console to a Vmware VM

Create a serial console with "socket (named pipe)" of "/tmp/socket", "from:server, to:virtual machine" in vmware player, etc.. gui. Run the above command after you have booted the guest OS (which should also be configured for serial console).

Comments (3) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
for i in $(multipath -ll | grep "3PARdata,VV"|awk '{print $1}') ; do parted -a optimal /dev/mapper/$i --script -- mklabel gpt mkpart primary 1 -1 set 1 lvm on ; done
2012-09-12 15:30:36
User: mhs
Functions: awk grep set
Tags: multipath parted
1
Up
Down
parted - scripted partitioning (of all multipathed SAN LUNs)

`multipath -ll` requires Device Mapper multipath.conf configuration. And of course, replace "3PARdata,VV" with your disk array's SCSI vendor,LUN name.

- GPT partition table allows you to create >2TB partitions

Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
for i in /sys/block/sd* ; do wwn=`/lib/udev/scsi_id -g -s /block/${i##*/}` ; [ "$wwn" != "" ] && echo -e ${i##*/}'\t'$wwn ;done
2012-09-12 14:14:53
User: mhs
Functions: echo
Tags: sysfs WWN LUNs scsi_id
1
Up
Down
Formatted list - WWNs of all LUNs

Use `scsi_id` to positively identify which LUNs are which (i.e. compare with the list of LUNs you created on your disk array)

(shown: RHEL5 usage)

Debian usage:

# for i in /dev/sd* ; do wwn=`/lib/udev/scsi_id -g --device $i` ; [ "$wwn" != "" ] && echo -e ${i##*/}'\t'$wwn ;done
Show sample output | Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
blkid -c /dev/null
2012-09-12 13:34:41
User: mhs
Tags: partition uuid sysfs blkid util-linux
2
Up
Down
detect partitions

`blkid` is an interface to libuuid - it can read Device Mapper, EVMS, LVM, MD, and regular block devices.

-c /dev/null - Do not use cached output from /etc/blkid.tab or /etc/blkid/blkid.tab (RHEL)

-i - Display I/O Limits (aka I/O topology) information (not available in RHEL)

-p - Low-level superblock probing mode (not available in RHEL)

Show sample output | Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
lsof -n -P|grep FlashXX|awk '{ print "/proc/" $2 "/fd/" substr($4, 1, length($4)-1) }'|while read f;do newname=$(exiftool -FileModifyDate -FileType -t -d %Y%m%d%H%M%S $f|cut -f2|tr '\n' '.'|sed 's/\.$//');echo "$f -> $newname";cp $f ~/Vids/$newname;done
2012-02-25 01:49:45
User: mhs
Functions: awk cp cut echo grep read sed tr
Tags: youtube flash flv exiftool tmpfs
8
Up
Down
Keep a copy of the raw Youtube FLV,MP4,etc stored in /tmp/

Certain Flash video players (e.g. Youtube) write their video streams to disk in /tmp/ , but the files are unlinked. i.e. the player creates the file and then immediately deletes the filename (unlinking files in this way makes it hard to find them, and/or ensures their cleanup if the browser or plugin should crash etc.) But as long as the flash plugin's process runs, a file descriptor remains in its /proc/ hierarchy, from which we (and the player) still have access to the file. The method above worked nicely for me when I had 50 tabs open with Youtube videos and didn't want to have to re-download them all with some tool.

Comments (1) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
exec -a "/sbin/getty 38400 tty7" your_cmd -erase_all_files
2012-02-01 10:54:03
User: mhs
Functions: exec
Tags: exec ps process table
16
Up
Down
Hide the name of a process listed in the `ps` output
exec -a $NAME $COMMAND $ARGS

`your_cmd -erase_all_files` is the real process, but harmless-looking getty appears in the process table.

Never actually had a need to do this, but interesting nonetheless... Tested in bash, dash.

-a $NAME

"pass NAME as the zeroth argument to COMMAND", i.e. customise the name of the process (as commonly seen with `ps`)

Show sample output | Comments (2) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
lshw -short
2011-06-28 23:32:30
User: mhs
Tags: lshw ioscan
6
Up
Down
Show 'Hardware path'-style tree of all devices in Linux
Show sample output | Comments (2) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
echo "${0%/*}"
2011-04-17 12:09:56
User: mhs
Functions: echo
Tags: Process Management parameter expansion special parameters
10
Up
Down
Find out the starting directory of a script

Invoked from within a shell script, this will print the directory in which the script resides. Doesn't depend on external tools, /proc/self/*, etc.. (`echo` is a shell builtin.) To see the *current working* directory of a script, use `pwd`.

Comments (6) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
mailutil appenddelete '{src.mailsrv1.com:993/imap/norsh/notls/ssl/novalidate-cert/user="username"}INBOX' '{dest.mailsrv2.com:143/imap/norsh/notls/user="username"}INBOX'
2011-02-08 09:37:05
User: mhs
Tags: mailutil IMAP
2
Up
Down
move messages directly from one IMAP inbox to another

This one-liner was useful in helping someone I know to get off of MS Exchange. `mailutil` proved to be a much better alternative than `fetchmail` or `getmail` in this case.

It quickly moved all mails to the destination server (a simple Dovecot/Maildir setup), with no need to convert back and forth between mbox/maildir on the user's own system.

Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
for i in ~/.adobe ~/.macromedia ; do ( rm $i/ -rf ; ln -s /dev/null $i ) ; done
2010-12-29 13:23:48
User: mhs
Functions: ln rm
Tags: flash LSO cookies
18
Up
Down
Stop Flash from tracking everything you do.

Brute force way to block all LSO cookies on a Linux system with the non-free Flash browser plugin. Works just fine for my needs. Enjoy.

Show sample output | Comments (5) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
xfreerdp --plugin rdpsnd -g 1280x720 -a 24 -z -x m -u $username -p $password 10.20.30.40
2010-12-29 11:21:18
User: mhs
Tags: rdesktop RDP
2
Up
Down
Open Remote Desktop (RDP) from command line having a custom screen size

This example uses xfreerdp, which builds upon the development of rdesktop. This example usage will also send you the remote machine's sound.

Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
perl -wlne'/title>([^<]+)/i&&rename$ARGV,"$1.html"' *.html
2010-12-29 05:39:41
User: mhs
Functions: perl
Tags: rename
9
Up
Down
Rename HTML files according to their title tag

The above one-liner could be run against all HTML files in a directory. It renames the HTML files based on the text contained in their title tag. This helped me in a situation where I had a directory containing thousands of HTML documents with meaningless filenames.

Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
infocmp rxvt-unicode | ssh 10.20.30.40 "mkdir -p .terminfo && cat >/tmp/ti && tic /tmp/ti"
2010-12-29 00:44:49
User: mhs
Functions: ssh
Tags: terminfo
3
Up
Down
Send your terminfo to another machine

I frequently use this trick to send my terminal settings to HPUX and older RHEL systems. This is due to the fact that terminfo support for rxvt-unicode (my preferred terminal app) does not exist on many older Linux and Unices.

Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
file -s /dev/sd*
2010-12-28 09:56:03
User: mhs
Functions: file
Tags: file devfs
24
Up
Down
Use file(1) to view device information

file(1) can print details about certain devices in the /dev/ directory (block devices in this example). This helped me to know at a glance the location and revision of my bootloader, UUIDs, filesystem status, which partitions were primaries / logicals, etc.. without running several commands.

See also:

file -s /dev/dm-* file -s /dev/cciss/*

etc..

Show sample output | Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate