sync

Author: cirosantilli

README.md

@@ -1,6 +1,6 @@
 # Linux Cheat ![logo](logo.jpg)
 
-Linux tutorials and cheatsheets. Minimal examples. User and kernel land.
+Linux tutorials and cheatsheets. Minimal examples. Mostly user-land.
 
 Includes Linux concepts and utilities that work on Linux, not necessarily in the LSB. So this is a big dump of useful things, and when something gets big / useful enough, I split to another repository.
 
@@ -33,14 +33,16 @@ Includes Linux concepts and utilities that work on Linux, not necessarily in the
     1. [sysctl](sysctl.md)
     1. [dmesg](demesg.md)
     1. [installkernel](installkernel.md)
+    1. [TTY](tty.md)
 1.  Initialization
     1.  [Install Operating System](install-operating-system.md)
     1.  [Boot](boot.md)
     1.  [Init](init.md): System V, Upstart
 1.  System information
     1.  [lsb_release](lsb_release.md)
     1.  [uname](uname.md)
-    1.  Hardware
+    1.  [Hardware](hardware.md)
+        1. [lshw](lshw.md)
         1. [cpuid](cpuid.md)
         1. [lspci](lspci.md)
         1. [lsusb](lsusb.md)
@@ -134,9 +136,11 @@ Includes Linux concepts and utilities that work on Linux, not necessarily in the
     1. [paste](paste.md)
     1. [printf](printf.sh)
     1. [sed](sed.sh)
+    1. [split](split.md)
     1. [strings](strings.md)
     1. [tabs](tabs.md)
     1. [uniq](uniq.md)
+    1. [uuencode](uuencode.md), `uudecode`
     1. [wc](wc.md)
 1.  Binary data viewers
     1. [hd](hd.md)
@@ -181,6 +185,7 @@ Includes Linux concepts and utilities that work on Linux, not necessarily in the
     1.  [pwd](pwd.sh)
     1.  [sleep](sleep.sh)
     1.  [strace](strace.md)
+    1.  [time](time.md)
     1.  [timeout](timeout.md)
     1.  [umask](umask.md)
     1.  [ulimit](ulimit.md)
@@ -196,7 +201,9 @@ Includes Linux concepts and utilities that work on Linux, not necessarily in the
         1. [avconv](avconv.md)
     1.  [Book](book.md): PDF, DJVU.
     1.  [Dictionary](dictionary.md): dictionary formats
+    1.  [Font](font.md)
     1.  [Game](game.md): games, emulation
+        1.  [Game engines](game-engines.md)
     1.  [Image](image.md)
         1.  [Formats](image-formats.md)
             1. [NetPBM](netpbm/)
@@ -230,14 +237,23 @@ Includes Linux concepts and utilities that work on Linux, not necessarily in the
     1. [id](id.md)
     1. [usermod](usermod.md)
 1.  [Desktop](desktop.md)
+    1.  Configuration methods
+        1.  [dconf](dconf.md)
+        1.  [gconf](gconf.md)
+        1.  [Desktop files](desktop-files.md)
     1.  [X11](x11.md)
+        1.  [wmctrl](xmctrl.md)
+        1.  [xprop](xprop.md)
+        1.  [xsel](xsel.md)
+        1.  [xset](xset.md)
+        1.  [Display manager](display-manager.md)
     1.  [freedesktop.org](freedesktop-org.md)
         1.  [D-Bus](dbus.md)
-    1.  [Display manager](display-manager.md)
         1. [LightDM](lightdm.md)
     1.  [Window manager](window-manager.md)
     1.  [Default applications](default-applications.md)
-        1. [update-alternatives](update-alternatives.md)
+        1.  [xdg-open](xdg-open.md)
+        1.  [update-alternatives](update-alternatives.md)
     1.  [Startup programs](startup-programs.md)
     1.  Notifications
         1. [libnotify](libnotify.md)
@@ -250,9 +266,6 @@ Includes Linux concepts and utilities that work on Linux, not necessarily in the
     1.  [logkeys](logkeys.md)
     1.  [setleds](setleds.md)
     1.  [solaar](solaar.md)
-    1.  [xsel](xsel.md)
-    1.  [xdg-open](xdg-open.md)
-    1.  [xset](xset.md)
 1.  Generic data formats
     1. [JSON](json.md)
     1. [XML](xml/)
@@ -299,6 +312,7 @@ Includes Linux concepts and utilities that work on Linux, not necessarily in the
         1. [acyclic](acyclic.md)
         1. [dijkstra](dijkstra.md)
         1. [gc](gc.md)
+    1.  [Statistics](statistics.md)
 1.  Packages
     1. [util-linux](util-linux.md)
 1.  Simulation
@@ -309,7 +323,6 @@ Includes Linux concepts and utilities that work on Linux, not necessarily in the
         1.  [anacron](anacron)
     1.  [logrotate](logrotate.md)
     1.  [xargs](xargs.md)
-1.  [Statistics](statistics.md)
 1.  [Bibliography](bibliography.md)
 
 ## WIP
@@ -319,8 +332,6 @@ Includes Linux concepts and utilities that work on Linux, not necessarily in the
     1. [eCryptfs](ecryptfs.md)
     1. [rootfs](rootfs.md)
     1. [MAKEDEV](makedev.md)
-1.  [Hardware](hardware.md)
-    1.  [lshw](lshw.md)
 1.  [gcov](gcov.md)
 1.  File sharing
     1. [NFS](nfs.md)

alternatives.md

@@ -15,3 +15,8 @@ Strict real time:
 - <https://en.wikipedia.org/wiki/QNX>, proprietary, micro-kernel, bought by BlackBerry.
 - <https://en.wikipedia.org/wiki/VxWorks>, proprietary
 - <https://en.wikipedia.org/wiki/ECos> GPL, started by Cygnus, discontinued by Red Hat, copyright later transfered to the FSF.
+- <https://en.wikipedia.org/wiki/FreeRTOS>
+
+Dedicated OSes / firmware:
+
+- <https://en.wikipedia.org/wiki/Rockbox> , music players

audio/README.md

@@ -38,7 +38,6 @@ Play file once and exit:
 
 Terminates when over. Good option to play an alarm signal after a very long command:
 
-
     sleep 5 && play ~/share/sounds/alert.*
 
 ### aplay
@@ -51,6 +50,10 @@ Comes with Ubuntu 12.04, but did not work very well.
 
 SoX package. Similar to `paplay`.
 
+Play `.raw` file:
+
+    play -b 16 -c 1 --endian big -e unsigned -r 44100 in.raw
+
 ### cplay
 
 ncurses CLI.

audio/codecs.md

@@ -34,8 +34,57 @@ Synthetic generation of pure tone + to PCM FFmpeg C API decode example: <https:/
 
 ## Raw formats
 
+### Raw
+
+No metadata, just bytes.
+
+<https://en.wikipedia.org/wiki/Raw_audio_format>
+
+This leaves the format unspecified: you should at least specify:
+
+- sampling rate
+- number of bits per byte
+- endianess
+- number of channels
+- type of data (signed, unsigned, floating-point, mu-law, a-law, ...)
+
+`ffplay` from FFmpeg and `play` from SoX can play it.
+
+- <http://stackoverflow.com/questions/20314739/how-to-play-pcm-sound-file-in-ubuntu>
+- <http://superuser.com/questions/76665/playing-a-pcm-file-on-a-unix-system>
+
+### WAV
+
+IBM, Windows. Widely Linux implemented.
+
+<https://en.wikipedia.org/wiki/WAV>
+
+Is a RIFF format <https://en.wikipedia.org/wiki/Resource_Interchange_File_Format>
+
+Contains metadata, so unlike RAW it contains enough data for players to play it properly.
+
 ### PCM
 
+TODO? vs raw?
+
 <https://en.wikipedia.org/wiki/Pulse-code_modulation>
 
 Decoded from MP2: <https://github.com/FFmpeg/FFmpeg/blob/1ec7a703806049265991723a8826bd61555edef4/doc/examples/decoding_encoding.c>
+
+### AIFF
+
+Apple, derived from IFF (Acorn).
+
+<https://en.wikipedia.org/wiki/Audio_Interchange_File_Format>
+
+## Theory
+
+44100 Hz is a common sampling frequency: <https://en.wikipedia.org/wiki/44,100_Hz>
+
+Humans hear between 20 and 20k Hz.
+
+https://en.wikipedia.org/wiki/Nyquist–Shannon_sampling_theorem implies that at least 40k is needed on a perfect system.
+
+## MIDI
+
+TODO what is this?

chat.sh

@@ -2,65 +2,63 @@
 
 # Chat utilities, specially command line ones.
 
-## mseg write wall
+# Write messages to other users on the system.
 
-  # Write messages to other users on the system.
+## mseg
 
-  ## mseg
+  # Enable/disable messages:
 
-    # Enable/disable messages:
+    mseg n
+    mseg
+      #n
+    mseg y
+    mseg
+      #y
 
-      mseg n
-      mseg
-        #n
-      mseg y
-      mseg
-        #y
+## write
 
-  ## write
+  # Write to a user in a TTY:
 
-    # Write to a user in a TTY:
+    u=
+    write $u tty3
 
-      u=
-      write $u tty3
+  # Now:
 
-    # Now:
+  # - type you message
+  # - type enter, and it is sent
+  # - hit Ctrl + D and its over
 
-    # - type you message
-    # - type enter, and it is sent
-    # - hit Ctrl + D and its over
+    u=
+    h=
+    sudo write $h@$u tty2
 
-      u=
-      h=
-      sudo write $h@$u tty2
+## wall
 
-  ## wall
+  # Write to all:
 
-    # Write to all:
+    wall
 
-      wall
+  # Type you message. It is only sent after you ctrl+d
 
-    # Type you message. It is only sent after you ctrl+d
+  # Sends to all even if disabled:
 
-    # Sends to all even if disabled:
+    sudo wall
 
-      sudo wall
+  # Play with it:
 
-    # Play with it:
-
-      #go to tty3. on ubuntu: ctrl+alt+f3
-      #login as user u
-      mesg y
-      #go to tty7 (xserver). on ubuntu: ctrl+alt+f7
-      sudo write u tty3
-      #write
-      #go to tty3
-      #your message is there!
+    #go to tty3. on ubuntu: ctrl+alt+f3
+    #login as user u
+    mesg y
+    #go to tty7 (xserver). on ubuntu: ctrl+alt+f7
+    sudo write u tty3
+    #write
+    #go to tty3
+    #your message is there!
 
 ## talk
 
   # Commandline chat program.
 
-  # POSIX.
+  # POSIX, but not intall on Ubuntu by default:
 
-    sudo aptitude install -y talk
+    #sudo aptitude install -y talk

date.md

@@ -12,7 +12,7 @@ Sample output:
 
 Format current time and output it:
 
-    date '+%Y-%m-%d %H:%M:%S'
+    date '+%Y-%m-%d_%H:%M:%S'
 
 Sample output:
 

dconf.md

@@ -0,0 +1,82 @@
+# dconf
+
+DConf is the new backend for gsettings.
+
+It used in Ubuntu 15.10 to store many desktop settings. `unity-control-center` is basically a front-end for it, and many default applications store their settings there.
+
+Completely separate schema to gconf.
+
+It should be used on new apps instead of gconf.
+
+## ~/.config/dconf/user
+
+File that stores all dconf settings.
+
+Binary database format, which implies:
+
+- fast to parse. Specially important as startup
+- not human readable. But you can export and import plain-text `.conf` file representations with `dconf dump` and `dconf load`.
+- corruption of part of it can kill all the data in one go.
+- not portable across OSes. Would be a good choice for apps if not for this.
+
+## dconf utility
+
+View all dconf configs at once in plain-text:
+
+    dconf dump / >~/.config/dconf/user.conf
+
+Reload plain-text settings:
+
+    dconf load / <~/.config/dconf/user.conf
+
+Change one setting:
+
+    dconf write org/gnome/gnome-screenshot/auto-save-directory "/home/ciro"
+
+Print to stdout whenever a setting changes:
+
+    dconf watch /
+
+So when you use some GUI to change things, you know what is going on.
+
+## dconf-editor
+
+GUI editor for dconf
+
+    dconf-editor
+
+## gsettings
+
+gsettings is a frontend for both dconf on Linux, and possibly other backends on other systems such as the Windows registry (binary).
+
+Therefore, applications should only use it directly, and not dconf, to achieve greater portability.
+
+On current GNOME based desktops, it does not support GConf.
+
+Set the value of a key:
+
+    gsettings set 'org.gnome.gnome-screenshot' 'auto-save-directory' 'file:///home/$USER/screenshot'
+
+Normal not hidden scroll bars:
+
+    gsettings set com.canonical.desktop.interface scrollbar-mode normal
+
+Show username on panel:
+
+    gsettings set com.canonical.indicator.session show-real-name-on-panel true
+
+Return key to its default value:
+
+    gsettings reset com.canonical.desktop.interface scrollbar-mode
+
+## dconf vs gconf vs gsettings
+
+Applications can them to manage user preferences. in key/value manner, where keys are put in a `/` separated tree.
+
+Created by the gnome project.
+
+Sources:
+
+- <http://askubuntu.com/questions/22313/what-is-dconf-what-is-its-function-and-how-do-i-use-it>
+- <http://askubuntu.com/questions/249887/gconf-dconf-gsettings-and-the-relationship-between-them>
+- gconf vs dconf: <http://askubuntu.com/questions/34490/what-are-the-differences-between-gconf-and-dconf>