Commands file.

Quick command reference for mwnn.

1 X server
- 1.1 Enable/Disable DPMS (Energy Star) features.
2 CD/DVD burn
3 GPG usage
- 3.1 Encrypt/Decrypt messages.
4 youtube-dl
5 MPlayer
6 Mencoder
7 FFMPEG
8 Wireshark
9 SQLite
10 GNU Emacs
- 10.1 Keyboard macros
- 10.2 Search and replace
- 10.3 Registers
- 10.4 Rectangles
- 10.5 Org-mode
- 10.6 CScope
- 10.7 Server
- 10.8 Printing
- 10.9 Flymake configuration
- 10.10 Miscellaneous
11 VSFTPD
- 11.1 Enable local users login
12 Synaptic touchpad
- 12.1 Enable tap on synaptic touchpad
13 GDB
14 Python
15 tmpfs
16 Info pages.
17 IP tables
18 WGet
19 ARPing
20 GNU configure
- 20.1 Installation directory
- 20.2 Cross compilation
21 Git
22 Imagemagick
23 CScope
24 GCC
25 xterm
26 tcpdump
27 Linux kernel
- 27.1 Get kernel state information
28 IPv6
29 rtorrent
30 grep
31 Fedora
32 xz
33 Openssl
34 Curl
35 Split and join files
36 User and group management
37 Miscellaneous

1 X server

1.1 Enable/Disable DPMS (Energy Star) features.

Switch off monitor immediately.
```
$ xset dpms force off
```
Disable DPMS.
```
$ xset -dpms
```
Enable DPMS.
```
$ xset +dpms
```
Switch off monitor after 2 seconds of inactivity.
```
$ xset dpms 2
```

2 CD/DVD burn

Create an iso image out of the data that needs to be burnt.

$ mkisofs -r -V <CD/DVD name> -o filename.iso dir1/ dir2/

Get the device identifier of the CD/DVD burner.
```
# cdrecord -scanbus
```
For non-multisession writes use the following command.
```
# cdrecord -v speed=8 dev=1,0,0 -data filename.iso.
```

For multisession writes use the -multi option.

# cdrecord -v speed=8 dev=1,0,0 -multi -data filename.iso

3 GPG usage

3.1 Encrypt/Decrypt messages.

Generate a public/private key pair.
```
$ gpg --gen-key
```
If other people would want to send messages to us, we would have to give our public key to them. So we export our public key to a file.
```
$ gpg --armor --export "NAME OF THE KEY" > public_key.txt
```
Email the key to the people who want to send us messages.
To import other people's public key use the following command:
```
$ gpg --import public_key.txt
```
To encrpyt a message that needs to be sent to another person do the following:
```
$ gpg --armor --encrypt message.txt
```
A new file called message.txt.asc will be created containing the encrypted data.
To decrypt the data at the recipient's end do the following:
```
$ gpg --decrypt message.txt.asc
```

4 youtube-dl

Use the following command to download high definition video:
```
$ youtube-dl -b -d URL
```
To continue downloading a partially downloaded file use the -c option:
```
$ youtube-dl -c -b -d URL
```
Let youtube-dl decide the file extension (mp4 or flv) based on the type of the video file being downloaded.
```
$ youtube-dl -b -o 'sunny_boney_m.%(ext)s' http://www.youtube.com/watch?v=yD8DcgpLp_w
```

5 MPlayer

To invoke mplayer in quiet mode use one of the following commands:

$ mplayer -quiet <media file>

$ mplayer -really-quiet <media file>

To construct an index (for seeking through a partially downloaded media file) use the following command:
```
$ mplayer -quiet -idx <media file>
```
To get timing information type the letter 'o'.
To flip the video upside-down use the following command:
```
$ mplayer -flip <video file>
```
To start viewing a movie in fullscreen mode use the following command:
```
$ mplayer -fs <video file>
```
Play DVD content
```
$ mplayer -nocache dvdnav://
```

6 Mencoder

Obtain crop information

$ mplayer dvd://<track number> -chapter 2 -vf cropdetect

Rip a DVD to XviD format

1st Pass

$ mencoder dvd://<track number> -vf crop=720:352:0:62 -ovc xvid -xvidencopts bvhq=1:chroma_opt:quant_type=mpeg:bitrate=658:pass=1 -oac copy -o /dev/null

2nd Pass

$ mencoder dvd://<track number> -vf crop=720:352:0:62,scale=704:304 -ovc xvid -xvidencopts bvhq=1:chroma_opt:quant_type=mpeg:bitrate=658:pass=2 -alang en -oac mp3lame -lameopts br=96:cbr:vol=6 -o rang_de_basanti.avi

Rip a VCD

$ mencoder vcd://<track number> -o movie.avi -ovc lavc -oac lavc

Transcode (convert) videos to MP4 format (so that they becomes playable on IPod).

$ mencoder input.avi -sws 9 -of lavf -lavfopts format=mp4  -vf scale=576:320,dsize=576:320,harddup  -ovc x264  -x264encopts bitrate=1381:vbv_maxrate=1500:vbv_bufsize=2000:nocabac:me=umh:trellis=1:level_idc=30:global_header:threads=2:pass=1:turbo  -oac faac  -faacopts mpeg=4:object=2:br=160:raw -channels 2 -srate 48000 -o output.mp4

Cut a portion from a video file.

$ mencoder -ss <start position (in secs)> -endpos <end position/step size (in secs)> <input file> -ovc copy -oac copy -o <output file>

7 FFMPEG

Convert *.avi files to *.mp4 (to be able to play media files on IPod)

$ ffmpeg -i extreme_ways.avi -s 480x320 -aspect 16:9 -b 768k -ab 64k -ar 22050 -r 30000/1001 extreme_ways.mp4

8 Wireshark

Use editcap to edit *.pcap files.
The -d option lets you remove duplicate packets in a capture.
```
$ editcap -d infile.pcap outfile.pcap
```
To select a particular range of packets do the following:
```
$ editcap -r infile.pcap outfile.pcap start-end
```
Here start/end indicate the packet range that is required to be included in the outfile.pcap file. The -r option causes the packets whose packet numbers are specified on the command line to be written to the output capture file, instead of discarding them.
To delete a particular range of packets do the following:
```
$ editcap infile.pcap outfile.pcap start-end
```
Start a capture immediately on wireshark startup:
```
$ wireshark -k
```
Start a capture on a particular network interface:
```
$ wireshark -i <interface name>
```
Save the capture to a file:
```
$ wireshark -w <filename>
```
Stop capturing after 'n' seconds:
```
$ wireshark -a duration:n
```

9 SQLite

To execute a set of SQL/meta commands from a file use the following command line:
```
$ sqlite3 -init <filename>
```
To execute a set of SQL/meta commands on SQLite startup add the required commands to the ~/.sqliterc file.

10 GNU Emacs

10.1 Keyboard macros

To start a keyboard macro do the following:
```
C-x (
```
The end a keyboard macro do the following:
```
C-x )
```
To execute a previously defined keyboard macro do the following:
```
C-x e
```
To edit a keyboard macro:
```
C-x C-k
```
Assign a name to the keyboard macro
```
C-x C-k n
```

Get the Lisp code for a named macro

M-x insert-kbd-macro <RET> macroname <RET>

10.2 Search and replace

To do a regular-expression search & replace do the following:
```
M-x replace-regexp <RET> REGEXP <RET> NEWSTRING <RET>
```
When performing a "search and replace" operation, type the following to insert a newline character,
```
C-q C-j
```

10.3 Registers

To view the contents of a register:
```
M-x view-register <RET> <REGISTER>
```
To save a posistion in a register:
```
C-x r <SPC> <REGISTER>
```
To jump to a posistion saved in a register:
```
C-x r j <REGISTER>
```
To save text in a register:
```
C-x r s <REGISTER>
```
To insert text saved in a register:
```
C-x r i <REGISTER>
```
To save a number in a register:
```
C-u <NUMBER> C-x r n <REGISTER>
```
To increment the number in a register:
```
C-u <NUMBER> C-x r + R
```
Save current window configuration in a register
```
C-x r w <REGISTER>
```

10.4 Rectangles

Create a rectangle region by placing mark on a column and point on another column.
Kill a rectangle region of text.
```
C-x r k
```
Delete a rectangle region of text.
```
C-x r d
```
Yank/Paste previously killed/Cut rectangle region.
```
C-x r y
```
Replace a rectangle region with a string.
```
C-x r t STRING
```

10.5 Org-mode

Use cursor keys to move to previous/next weeks in Agenda mode.
The following #+keywords seem to be helpful:
```
#+AUTHOR
#+EMAIL
#+DATA
#+TITLE
#+TEXT
```
To assign a specific TODO keyword to an entry in the tree
```
C-<EntryNumber> C-c C-t
```
To insert a Timestamp with repeating interval, insert the timestamp and append +Nd (days), +Nw (weeks), +Nm (months), +Ny (years). The following repeats the task every month on the specified date.
```
<2009-11-02 Mon +1m>
```
To insert a timestamp (with hrs:min):
```
C-u C-c .
```
To specify a different lead time for DEADLINES:
```
<2009-11-02 Mon -5d>
```
To schedule an appointment use a plain timestamp i.e. Don't mark the timestamp with either DEADLINES/SCHEDULED keywords.
Insert a DEADLINE with a timestamp:
```
C-c C-d
```
Insert a SCHEDULE with a timestamp:
```
C-c C-s
```
To view the list of all STUCK projects (projects with no TODO keywords associated with them):
```
C-c a #
```
To sort the table based on the contents of a column, place the cursor on one of the column entries and type the following command.
```
C-c ^
```
Insert a horizontal line below the current line.
```
C-c -
```
For calculation purposes, use $n notation to represent columns. For example, $3 = ($1 + $2) / 2 is a formula that sets the third column with the average of values in first and second columns.
To apply a pre-defined formula on a column use,
```
C-c =
```
To define a formula for a column use,
```
C-u C-c =
```
Create a sparse tree matching a regex.
```
C-c / r
```
Export a sparse tree.
```
C-c C-e v
```
Create a footnote.
```
C-c C-x f
```
Calculate the sum of all the numbers in the current column.
```
C-c +
```
List the references of field in a table.
```
C-c ?
```
Toggle the display of a grid in a table.
```
C-c }
```

10.6 CScope

Add the following lines to your .emacs file.

(if (file-exists-p "~/software/emacs_extras/xcscope/xcscope.el")
    (progn
    (add-to-list 'load-path "~/software/emacs_extras/xcscope/")
    (require 'xcscope)
    (setq cscope-do-not-update-database t)))

Copy xcscope.el (from the standard CScope distribution) into one the directories listed under load-path.
Copy the shell script cscope-indexer (from the standard CScope distribution) into one of the directories listed by the PATH environmental variable.
Create a symbol cross-reference file.
```
C-c s I
```
Find all occurences of a symbol.
```
C-c s s
```
Find the global definition of a symbol.
```
C-c s g
```
Find the list of functions calling a particular function.
```
C-c s c
```
Find the functions called by a function.
```
C-c s C
```
Find all occurences of a text string.
```
C-c s t
```
Go to the next result listed in the CScope buffer.
```
C-c s n
```
Go to the previous result listed in the CScope buffer.
```
C-c s p
```

10.7 Server

Do not wait for the Emacs server to return.
```
$ emacsclient -n <filename>
```

10.8 Printing

Print current buffer along with its properties (like faces, etc).
```
M-x ps-print-buffer-with-faces
```

10.9 Flymake configuration

In .emacs file, Set the flymake-buildfile-dirs variable to the directory containing the Makefile.
```
(setq flymake-buildfile-dirs "/../")
```

Add the following lines in the Makefile:

# Flymake configuration.
ifneq($(CHK_SOURCES), )
check-syntax: $(patsubst %.c, %.o, $(shell basename $(CHK_SOURCES)))
endif

NOTE: There must be a rule for building the C source file.

10.10 Miscellaneous

Align text around a specified character.
```
M-x align-regexp
```
List all lines matching a regular expression.
```
M-x occur
```
To align a paragraph inside a C comment, select the paragraph and type,
```
M-q
```
To balance all the windows in an emacs session,
```
M-x balance-windows
```
or you can use the following shortcut
```
C-x +
```
List all key bindings.
```
M-x make-command-summary
```

11 VSFTPD

11.1 Enable local users login

Add the following to /etc/vsftpd.conf
```
anonymous_enable=NO
local_enable=YES
```

12 Synaptic touchpad

12.1 Enable tap on synaptic touchpad

To list all the Synaptics driver options do the following:
```
$ synclient -l
```
To enable TAP on the touchpad do the following:
```
$ synclient TapButton1=1
```

13 GDB

Display all the elements of an array.
```
(gdb) set print elements 0
```
Remove limits on the size of the call stack.
```
(gdb) set height 0
```
Display the contents of a memory area of size 20 bytes in binary format.
```
(gdb) x/20tb gen_ptr
```

14 Python

To go through the HTML version of python module documentation:
```
$ pydoc -p <port number>
```
Type in http://localhost:<port number> in a web browser.
Enter interactive mode after executing a script:
```
$ python -i <script name>
```

15 tmpfs

Create a tmpfs

# mount -t tmpfs -o size=1G,nr_inodes=10k,mode=0700 tmpfs /mnt/mwnn_tmpfs/

Change the size of the tmpfs filesystem on-the-fly:
```
# mount -o remount,size=2G /mnt/mwnn_tmpfs/
```

16 Info pages.

To update info's main page:

# cd /usr/share/info
# install-info mod_name.gz dir

17 IP tables

Delete a rule:

# iptables -D <chain name> <rule number>

18 WGet

Set pre-defined settings in ~/.wgetrc file. Example:

continue = on
progress = dot
timeout = 40
tries = 100

Download the contents of a remote directory recursively.
```
$ wget -r -nH --cut-dirs=5 ftp://ftp.slackware.com/pub/slackware/slackware-13.0/patches/packages/linux-2.6.29.6-3
```
The –cut-dirs=5 in the above command would cut the first 5 components of the URL specified as the argument.

19 ARPing

To know the MAC address of a remote machine:

# arping <IP addr>

20 GNU configure

20.1 Installation directory

Installation directory can be specified using the –prefix option.
```
$ ./configure --prefix=/usr/local/
```

20.2 Cross compilation

–build=BUILD

The system on which the package is built.

–host=HOST

The system where built programs and libraries will run. For simple
cross-compilation, only --host=HOST is needed.

–target=TARGET

Used only when building compiler tools; The system for which the tools will
create output.

–program-prefix=PREFIX

Prepend PREFIX to installed program names.

–program-suffix=SUFFIX

Append SUFFIX to installed program names.

–program-transform-name=PROGRAM

Run 'sed PROGRAM' on installed program names.

To install the built package in a different directory (so that the built package can be installed on different machines), use the DESTDIR variable when invoking 'make install'.
```
$ make DESTDIR=~/built_packages/prg_name install
```
'configure' options are passed recursively to all sub-packages. The following command shows the help associated with all sub-packages.
```
$ ./configure --help=recursive
```

21 Git

To resolve merge conflicts, do the following:
```
$ git add <filename>
$ git commit
```
To perform commits for certain hunks do the following:
```
$ git add -i
```
Select the patch option and then go ahead and select the hunks to be commited.
To enable auto-completion of Git commands in bash do the following:
- Copy the file contrib/completion/git-completion.bash (from the standard GIT source distribution) to ~/.git-completion.bash.
```
$ cp contrib/completion/git-completion.bash ~/.git-completion.bash
```
- Add the following line to your .bashrc file.
```
source ~/.git-completion.bash
```
List the files that was created/modified during each commit.
```
$ git whatchanged
```

Create a tar-ball from a tag.

$ git archive --format=tar --prefix=git-1.7.0.2/ v1.7.0.2 | bzip2 > git-1.7.0.tar.bz2

Patch generation.
- Generate patch files for each commit made between HEAD^^^ and HEAD.
```
$ git format-patch HEAD^^^..HEAD
```
- Generate one patch file for all commits made between HEAD^^^ and HEAD.
```
$ git diff HEAD^^^..HEAD > file.patch
```

Stash

Stash away temporary changes.
```
$ git stash save <stash message>
```
List all stashes.
```
$ git stash list
```
Apply a stash.
```
$ git stash apply <stash name>
```

Log
- Show all non-merge commits
```
$ git log --no-merges
```
- Show all commits authored by person X
```
$ git log --author=X
```
- Show all commits that contain a keyword.
```
$ git log --grep=<keyword>
```

22 Imagemagick

Screenshot of a window
```
$ import -window root screenshot.png
```

23 CScope

Create a symbol cross-reference table only for selected files.
```
$ cscope file1.c file2.c
```
Include source files in other directories (as well as the current directory).
```
$ cscope -s dir1, dir2, dir3
```
Build cross-reference for files listed in a text file.
```
$ cscope -i file_list.txt
```
Include header files present in other directories. By default, CScope searches for include-ed header files in the current directory. To include other directories in the search path, use the -I option.
```
$ cscope -I dir
```
This option can be specified more than once on the command line.
Specify a name for the file holding symbol cross-reference table.
```
$ cscope -f project_sym.out
```
Do not check for modified source files during start-up.
```
$ cscope -d
```
Build an inverted index database (for quicker symbol look-up).
```
$ cscope -q
```
The above command would create two more files (in addition to cscope.out). They are cscope.in.out and cscope.po.out.

24 GCC

Show the commands executed during each stage of compilation.
```
$ gcc -v file.c -o file
```
Disable removal of "NULL pointer check" code during optimization.
```
$ gcc -fno-delete-null-pointer-checks file.c -o file
```
Insert invocations to user-defined functions at the entry and exit of all the functions in a program.
```
$ gcc -finstrument-functions file.c -o file.
```
Record the gcc command line used to compile sources into the resulting object/executable.
```
$ gcc -Wall -frecord-gcc-switches file.c -o file.
```
The command line can then be extracted from the object/executable by using the following command.
```
$ readelf --string-dump=.GCC.command.line <object/executable>
```

25 xterm

Increase the number of lines buffered by xterm.
```
$ xterm -sl <number of lines>
```
The default number of lines buffered is 64.
Disable colored fonts (produced by running applications).
```
$ xterm -cm
```

26 tcpdump

Save packet capture in a file (for later usage)
```
$ tcpdump -i <interface name> -s 65535 -w <output file>
```
The file can later be opened in wireshark for further analysis.

27 Linux kernel

Insert a kernel module along with any dependencies.
```
# modprobe <module name>
```
Get meta information of a Linux kernel module.
```
# modinfo <module name>
```
Get a list of module specific parameters
```
# modinfo -p <module name>
```
Display kernel slab cache information.
```
$ slabtop
```

27.1 Get kernel state information

NOTE: The following keyboard shortcuts work only when used in 'virtual console' sessions.

Print a register dump.
```
AltGr + Scroll lock
```
AltGr is the right Alt key.
Print the state of all the processes.
```
Ctrl + Scroll lock
```
Print memory usage details.
```
Shift + Scroll lock
```

If the output does not appear on the screen, use the dmesg command to view the contents of the kernel ring buffer.

28 IPv6

Openssh
```
$ ssh -6 <user>@<ipv6 addr>
```

29 rtorrent

To disable a tracker, select the appropriate tracker from the "Tracker" list and press the "*" key.

30 grep

Invert the selection.
```
$ grep -v <pattern>
```

31 Fedora

Install xterm fonts.
```
$ yum install xorg-x11-fonts-misc
```
Install US-English support for aspell.
```
$ yum install aspell-en
```

32 xz

Extract a *.xz file:
```
$ xz -d file.xz
```

Create a xz compressed tar ball:

$ tar cJf file.tar.xz file1 file2 file3

Extract a xz compressed tar ball:
```
$ tar xJf file.tar.xz
```

33 Openssl

Encrypt a file using AES algorithm.

$ openssl enc -aes-256-cbc -salt -in <input file> -out <output file>

Decrypt a file using AES algorithm.

$ openssl enc -d -aes-256-cbc -in <input file> -out <output file>

34 Curl

Send mail via a GMail account.
```
$ curl -n -v --ssl --mail-from <gmail-username@gmail.com> --mail-rcpt <to-email_id> --url smtp://smtp.gmail.com -T mail.txt
```
The login name and password must be located in the file $HOME/.netrc in the format indicated below:
```
machine smtp.gmail.com login <login name> password <password>
```
E-mail headers like SUBJECT and TO can be specified at the begining of the mail.txt file.

35 Split and join files

Split a large file into two or more files (for when copying a 4GB+ file onto a USB drive with FAT32 filesystem). The following command splits the Slackware 13.1 iso image into three files (slackwareaa, slackwareab & slackwareac).
```
$ split --bytes=2048m slackware-13.1-install-dvd.iso slackware
```
Join files that have been obtained after spliting a large file using split command.
```
$ cat slackwareaa slackwareab slackwareac > slackware-13.1-install-dvd.iso
```

36 User and group management

Add an user.
```
$ useradd -g <initial group> -G group1, group2 {, ...} -m <user name>
```
The above command also creates the /home/<username> directory if it does not exist.
Specify a password for a user.
```
$ passwd <user name>
```
The following is an interactive tool to add a user. It allows the administrator to set the password and groups for the new user.
```
$ adduser
```
Delete an existing user account.
```
$ userdel -r <user name>
```
The -r option is for deleting the user's home directory.
List the groups to which a user belongs to.
```
$ groups [user name]
```
Add a user to a group.
```
$ gpasswd -a <user name> <group name>
```
Delete a user from a group.
```
$ gpasswd -d <user name> <group name>
```
Create a new group.
```
$ groupadd <group name>
```
Delete an existing group.
```
$ groupdel <group name>
```

37 Miscellaneous

Rescan the SCSI subsystem for new devices (useful if your recently plugged-in USB device is not being detected automatically)
```
# rescan-scsi-bus
```
Format a drive with FAT32 as the filesystem type.
```
# mkdosfs -n <volume name> <device file> <block count>
```
The <block count> can be obtained by using fdisk -l on the <device file>.

Format a drive with EXT3 as the filesystem type.

# mkfs -t ext3 -v -L <volume name > <device file>

Create backup of all files changed while applying a patch:
```
$ patch -b -p0 < valgrind-3.5.0-glibc-2.11.patch
```
Display the local time equivalent of an UTC time.
```
$ date -d 'YYYY-MM-DD HH:MM UTC'
```

Interactively merge two files.

$ sdiff file_v1.c file_v2.c -o file_merge.c

Convert online manual pages to pdf files.

$ man -t sem_open | ps2pdf - sem_open.pdf

Convert a list of manual pages into a single pdf file,

$ man -t sem_open sem_unlink sem_post sem_wait | ps2pdf - semaphore.pdf

Author: mwnn

Date: <2010-05-17 Mon 10:19>

HTML generated by org-mode 7.3 in emacs 23

mwnnlin's web log

Command reference