Arkham's Eyrie » linux

Another 17 Vim Tips

Arkham — Tue, 06 Oct 2009 22:44:38 +0000

-k + e + ! – Write ‘è’ character.
-k + e + ‘ – Write ‘é’ character.
!!date – Insert date in current line.
g, / g; – Jump back/forward to the locations that have been edited.
zf – Fold selected text.
zfa} – Fold the function enclosing the cursor.
zR / zM – If foldmethod is set, open/close all folds.
-w + (-/+) – In splitted views, reduce/increase current zone height.
-w + (</>) – In splitted views, reduce/increase current zone width.
:vimgrep /pattern/ files – Search for pattern in the provided list of files.
:cn and :cN to jump between vimgrep results.
:clist to display all vimgrep result and :cc number to jump to a specific one.
:%s/\/or/g – Replace all occurences of “and” with “or”, leaving words like “demand” unchanged.
:%s/foo/bar/gi – Replace case insensitively.
* / # – Search for the next/previous occurence of the word under the cursor.
/\cfoo\Cbar/ – Matches “foobar”, “Foobar” and “FOObar”.
/$[a-z]$$[a-z]$\2\1/ – Matches “abba” and “deed”.

17 Vim Tips

Arkham — Mon, 05 Oct 2009 01:06:51 +0000

-o – Switch from insert mode to command mode for one single command.
vim +linenumber file – Open file at line number.
vim +/pattern file – Open file at first occurence of pattern.
:next files – Open a list of files, each in a new buffer.
:up[date] - Save a modified file.
“byy + “bp – Copy a line inside named buffer “b” and paste it.
-] – Follow green links in documentation pages.
-t – Go back to the previous documentation page.
>ap – Indent whole paragraph.
10dd + 2. – Delete 10 lines, repeat twice (delete 20 lines more).
VU – Make the whole line uppercase.
V10j + : + !sort – sort alphabetically next 10 lines.
:!uname -a – Display system information.
:! wc % – Display information about current file.
:r!uname -a – Insert system information into the next line.
gg=G – Reformat whole file.
-n – Start autocompletion.

Sed by examples, Part 2

Arkham — Mon, 29 Jun 2009 16:19:48 +0000

sed (stream editor) is a Unix utility which (a) parses text files and (b) implements a programming language which can apply textual transformations to such files.
It reads input files line by line (sequentially), applying the operation which has been specified via the command line (or a sed script), and then outputs the line.

Substitution

Substitute, for every line, the first occurence of foo (if any) with spam:

# test.txt
foo bar spam foo
spam foo bar egg
sausage foo spam egg
spam spam spam

sed -e 's/foo/spam/' test.txt

Substitute every occurence of foo with spam:
```
sed -e 's/foo/spam/g' test.txt
```
Substitute every occurence of foo with spam in the first two lines:
```
sed -e '1,2s/foo/spam/g' test.txt
```
Substitute every occurence of foo with spam in every line that starts with sausage and ends with egg:
```
sed -e '/^sausage.*egg$/s/foo/spam/g' test.txt
```

Substitute paths:

sed -e 's|/usr/bin/|/usr/local/bin|g' script.sh

Remove html tags:



Hello World!

sed -e 's/<[^>]*>//g' hello.html

Advanced substitution

Append (that’s what she said) to every line ( & represents what matches):
```
sed -e "s/^.*$/& (that's what she said)/g" test.txt
```

Append lol, rofl and lmao to the first three words of every line:

sed -e 's/\(^[^ ]*\) \([^ ]*\) \([^ ]*\)/\1lol \2rofl \3lmao/' test.txt

Multiple Commands

Print a file alternating row numbers:
```
sed -n -e '=;p' test.txt
```

Print some information about your cpu first core:

# script.sed
1,/^$/{
    /model name/p
    /flags/p
    /bogomips/p
}

sed -n -f script.sed /proc/cpuinfo

Add a line before/after each line or replace line:

# script.sed
i\
This line will be inserted before each line

# script.sed
a\
This line will be inserted after each line

# script.sed
c\
This line will be inserted in each line

sed -f script.sed test.txt

Sed by examples

Arkham — Sun, 28 Jun 2009 23:16:40 +0000

sed (stream editor) is a Unix utility which (a) parses text files and (b) implements a programming language which can apply textual transformations to such files.
It reads input files line by line (sequentially), applying the operation which has been specified via the command line (or a sed script), and then outputs the line.

Delete

Delete the first line of a file:
```
sed -e '1d' /etc/fstab
```
Delete from the second to the tenth line:
```
sed -e '2,10d' /etc/fstab
```
Delete lines starting with #:
```
sed -e '/^#/d' /etc/fstab
```

Print

Print lines starting with #:
```
sed -n -e '/^#/p' /etc/fstab
```
Print blocks of text enclosed by BEGIN and END:
```
sed -n -e '/BEGIN/,/END/p' script.awk
```

Print Device section in xorg.conf:

sed -n -e '/Section "Device"/,/EndSection/p' /etc/X11/xorg.conf

Print main function in a C source file:

sed -n -e '/main[[:space:]]*(/,/^}/p' source.c

How to colorize bash prompt easily

Arkham — Wed, 24 Jun 2009 18:02:34 +0000

Sometimes, the bash prompt can look a little dull and it may become difficult to recognize where the output of a command ends. Here I provide with a very simple way to customize your bash prompt by adding some colors.

First of all, add these colors definition to your .bashrc

## Fancy colors
red='\[\e[0;31m\]'
RED='\[\e[1;31m\]'
blue='\[\e[0;34m\]'
BLUE='\[\e[1;34m\]'
cyan='\[\e[0;36m\]'
CYAN='\[\e[1;36m\]'
black='\[\e[0;30m\]'
BLACK='\[\e[1;30m\]'
green='\[\e[0;32m\]'
GREEN='\[\e[1;32m\]'
yellow='\[\e[0;33m\]'
YELLOW='\[\e[1;33m\]'
magenta='\[\e[0;35m\]'
MAGENTA='\[\e[1;35m\]'
white='\[\e[0;37m\]'
WHITE='\[\e[1;37m\]'
NC='\[\e[0m\]' # No Color

The variables you want to use are

\u – username
\h – host name
\w – current absolute path
\W for current relative path
\$ – te prompt character (eg. ‘#’)

For example, my current setup looks like:

PS1="${green}\u${NC}@${green}\h ${BLUE}\w${NC} ${GREEN}\$ ${NC} "

Enjoy

Awk by examples

Arkham — Tue, 14 Apr 2009 14:27:40 +0000

AWK is a language for processing files of text. A file is treated as a sequence of records, and by default each line is a record. Each line is broken up into a sequence of fields, so we can think of the first word in a line as the first field, the second word as the second field, and so on. An AWK program is of a sequence of pattern-action statements. AWK reads the input a line at a time. A line is scanned for each pattern in the program, and for each pattern that matches, the associated action is executed.

Basics

Print /etc/mtab (awk reads a line at time and prints it) :
```
awk '{ print }' /etc/mtab
```
Print /etc/mtab ($0 denotes the whole line) :
```
awk '{ print $0 }' /etc/mtab
```
List mounted filesystems ($1 denotes the first element of the line) :
```
awk '{ print $1 }' /etc/mtab
```
List groups (-F chooses the Field Separator) :
```
awk -F":" '{ print $1 }' /etc/group
```
List groups and id (awk concatenates print() arguments) :
```
awk -F":" '{ print $1 " " $3 }' /etc/group
```

List groups and id (Nicer format) :

awk -F":" '{ print "group: " $1 "\tid: " $3 }' /etc/group

Launching external awk scripts :

# first.awk
BEGIN {
    FS=":"
}
{ print $1 }

awk -f first.awk /etc/mtab

List IPv4 addressess :
```
ifconfig | awk '/inet / { print $2 }'
```

List processes run by root :

# psroot.awk
$1 == "root" { 
    printf("ROOT: "); 
    for (i=11; i<=NF; i++) 
        printf("%s ", $i);
    printf("\n")
}

ps au | awk -f psroot.awk

Print X warnings :

awk '$1 ~ /(WW)/ { print }' /var/log/Xorg.0.log

Print a file removing comments :
```
awk '! /^#/ { print }' /etc/fstab
```

Print number of files/directories :

ls -lA |  awk 'BEGIN{ x=0 } { x=x+1 } END{ print x-1 }'

Awk as calculator :
```
echo | awk '{ print ((2*5^2-1)%7) }'
```

Count empty lines :

# blanklines.awk
BEGIN { x=0 } 
/^$/  { x=x+1 } 
END   { print "I found " x " blank lines :)" }

awk -f blanklines.awk /etc/profile

Use regexp as FS (note the difference though) :

echo '   a   b c  d '| awk -F"[ \t\n]+" '{ print $2 }'

echo '   a   b c  d '| awk -F" " '{ print $2 }'

Understand NR and NF :

# nrnf.awk
BEGIN { x=0 } 
      { print "Words on line " NR ": " NF ; x+=NF } 
END   { print "Total lines: " NR ; print "Total words: " x }

awk -f nrnf.awk nrnf.awk

Free your memory on Linux

Arkham — Thu, 18 Dec 2008 23:06:57 +0000

No, this is not a howto to make your RAM Stallman-compliant.

Sometimes, it is handy to empty your caches, like when Virtualbox checks the available memory before actually starting. From linux 2.6.16 there are some nice tricks for dropping the memory cache, dentries and inodes.

First of all, we need to free all the cached objects.
Run as root:

sync

Then, to free pagecache:

echo 1 > /proc/sys/vm/drop_caches

To free dentries and inodes:

echo 2 > /proc/sys/vm/drop_caches

To free pagecache, dentries and inodes:

echo 3 > /proc/sys/vm/drop_caches

Now, check your available memory using free and all your cache are belong to us.. *hu-uhm* ..should have been freed. Freed as in freed-om

KDE-like bigger icons for Gnome menu

Arkham — Wed, 22 Oct 2008 23:55:46 +0000

I’ve tried to use some kind of KDE like, bigger icons on my desktop for a while and I realized that it is really a pity to not use the wonderful 32×32 tango icons for the gnome menu also. If you want to try, it’s very simple:

gedit ~/.gtkrc-2.0

and put in this line:

gtk-icon-sizes = "panel-menu=32,32"

and restart gnome-panel (maybe you could be more gracious :P):

killall gnome-panel

Here is the outcome:

Colored Man Pages

Arkham — Wed, 24 Sep 2008 23:26:56 +0000

To improve your productivity when you’re reading long pages of fine manuals (aka when you’re doing some healthy RTFM), it is a very nice trick to add some colour in the terminal, so you can jump quickly from section to section or find the name of that sneaky option with a glance…

Add to your ~/.bashrc:

export LESS_TERMCAP_mb=$'E[01;31m'
export LESS_TERMCAP_md=$'E[01;31m'
export LESS_TERMCAP_me=$'E[0m'
export LESS_TERMCAP_se=$'E[0m'
export LESS_TERMCAP_so=$'E[01;44;33m'
export LESS_TERMCAP_ue=$'E[0m'
export LESS_TERMCAP_us=$'E[01;32m'

And

source ~/.bashrc

Mplayer and Nautilus “Open with”

Arkham — Thu, 19 Jun 2008 09:07:09 +0000

Nautilus “Open with” option and Mplayer don’t seem to behave correctly when the file we want to open contains spaces. The dirty hack to solve it is:

su
vi /usr/share/applications/mplayer.desktop

And replace “Exec=gmplayer %U” with “Exec=gmplayer %F”