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Articles taggués ‘commands’

Bash Shell: Replace a String With Another String In All Files Using sed and Perl -pie Options

28/09/2017 Comments off

String search and replace

How do I replace a string with another string in all files? For example, ~/foo directory has 100s of text file and I’d like to find out xyz string and replace with abc. I’d like to use sed or any other tool to replace all occurrence of the word.

The sed command is designed for this kind of work i.e. find and replace strings or words from a text file under Apple OX, *BSD, Linux, and UNIX like operating systems. The perl can be also used as described below.

sed replace word / string syntax

The syntax is as follows:
sed -i 's/old-word/new-word/g' *.txt

GNU sed command can edit files in place (makes backup if extension supplied) using the -i option. If you are using an old UNIX sed command version try the following syntax:

sed 's/old/new/g' input.txt > output.txt

You can use old sed syntax along with bash for loop:

#!/bin/bash
OLD="xyz"
NEW="abc"
DPATH="/home/you/foo/*.txt"
BPATH="/home/you/bakup/foo"
TFILE="/tmp/out.tmp.$$"
[ ! -d $BPATH ] && mkdir -p $BPATH || :
for f in $DPATH
do
  if [ -f $f -a -r $f ]; then
    /bin/cp -f $f $BPATH
   sed "s/$OLD/$NEW/g" "$f" > $TFILE && mv $TFILE "$f"
  else
   echo "Error: Cannot read $f"
  fi
done
/bin/rm $TFILE

A Note About Bash Escape Character

A non-quoted backslash \ is the Bash escape character. It preserves the literal value of the next character that follows, with the exception of newline. If a \newline pair appears, and the backslash itself is not quoted, the \newline is treated as a line continuation (that is, it is removed from the input stream and effectively ignored). This is useful when you would like to deal with UNIX paths. In this example, the sed command is used to replace UNIX path “/nfs/apache/logs/rawlogs/access.log” with “__DOMAIN_LOG_FILE__”:

#!/bin/bash
## Our path
_r1="/nfs/apache/logs/rawlogs/access.log"
 
## Escape path for sed using bash find and replace 
_r1="${_r1//\//\\/}"
 
# replace __DOMAIN_LOG_FILE__ in our sample.awstats.conf
sed -e "s/__DOMAIN_LOG_FILE__/${_r1}/" /nfs/conf/awstats/sample.awstats.conf  > /nfs/apache/logs/awstats/awstats.conf 
 
# call awstats
/usr/bin/awstats -c /nfs/apache/logs/awstats/awstats.conf

The $_r1 is escaped using bash find and replace parameter substitution syntax to replace each occurrence of / with \/.

perl -pie Syntax For Find and Replace

The syntax is as follows:
perl -pie 's/old-word/new-word/g' input.file > new.output.file

Categories: Système Tags: , , , ,

BASH: Vérifier qu’une commande existe

28/09/2017 Comments off

Comment vérifier qu’une commande existe en Bash ?
Comment vérifier la disponibilité des prérequis d’un script ?

Une méthode permettant de vérifier qu’une commande existe consiste à tester le retour de « command -v <commande_a_tester> » :

fhh@mafalda ~ $ command -v ls
alias ls='ls --color=auto'
fhh@mafalda ~ $ echo $?
0
fhh@mafalda ~ $ command -v ls > /dev/null && echo "ls existe" ls existe
 

Si la commande existe et est accessible via le PATH ou au chemin spécifié, « command -v » retourne « 0 », sinon, le retour est supérieur à « 0 » :

fhh@mafalda ~ $ command -v youhou
# youhou n'existe pas dans le PATH ou comme commande interne :
fhh@mafalda ~ $ echo $?
1
fhh@mafalda ~ $ command -v ../../usr/bin/date
# date est accessible au chemin spécifié :
fhh@mafalda ~ $ echo $?
0

Lire la suite…

Categories: Système Tags: , , ,

BASH : Suppression des accents, cédilles, etc

28/09/2017 Comments off

Comment supprimer les accents, cédilles, etc, dans une chaine de caractères ?

Méthode classique : la substitution

La suppression des caractères accentués et autres cédilles peut être effectuée, en Bash, en utilisant « sed » ou « tr » :

fhh@aaricia ~ $ _str="Une chaine avec des é, des Ù, des À, des ç et des œ"
fhh@aaricia ~ $ echo $_str | sed 'y/áàâäçéèêëîïìôöóùúüñÂÀÄÇÉÈÊËÎÏÔÖÙÜÑ/aaaaceeeeiiiooouuunAAACEEEEIIOOUUN/' Une chaine avec des e, des U, des A, des c et des œ

La méthode est fonctionnelle mais sous entend que tous les caractères à substituer aient été définis. Dans l’exemple, le « œ » n’a pas été remplacé car aucun caractère de remplacement ne lui est alloué.

Autre problème de cette méthode, remplacer une lettre par deux autres tel que « œ » par « oe » ou le « ß » allemand par « ss » nécessite la définition de règles particulières à chaque cas.

Ce sont ces raisons qui nous poussent à éviter cette méthode au profit de la conversion de chaines de caractères.

Méthode recommandée : la conversion

Plus complète, la méthode de conversion présente en sus l’avantage d’être plus concise.

« iconv » est utilisé pour « convertir » la chaine de caractères du format de base, UTF-8 dans l’exemple (option « -f » pour « from »), vers le format ASCII (option « -t » pour « to »).

Avec l’option « TRANSLIT », si un caractère ne peut être transcrit dans le format de destination, il est converti en une chaine de caractère équivalente.

fhh@aaricia ~ $ _str="Une chaine avec des é, des Ù, des À, des çÇ et des œ"
fhh@aaricia ~ $ echo $_str | iconv -f utf8 -t ascii//TRANSLIT Une chaine avec des e, des U, des A, des cC et des oe

La méthode fonctionne sur un large panel de caractères :

fhh@aaricia ~ $ echo "\"ß\"" | iconv -f utf8 -t ascii//TRANSLIT "ss"
fhh@aaricia ~ $ echo "āáǎàēéěèīíǐìōóǒòūúǔùǖǘǚǜĀÁǍÀĒÉĚÈĪÍǏÌŌÓǑÒŪÚǓÙǕǗǙǛ" | iconv -f utf8 -t ascii//TRANSLIT aaaaeeeeiiiioooouuuuuuuuAAAAEEEEIIIIOOOOUUUUUUUU

et peut être utilisée sur des fichiers :

fhh@aaricia ~ $ cat myfile.txt Une chaine avec des é, des Ù, des À, des ç et des œ   et même des "ß"
fhh@aaricia ~ $ iconv -f utf8 -t ascii//TRANSLIT < myfile.txt > noaccents.txt
fhh@aaricia ~ $ cat noaccents.txt Une chaine avec des e, des U, des A, des c et des oe   et meme des "ss"
 
Categories: Système Tags: , , , ,

Bash: How do I get the command history in a screen session?

05/07/2017 Comments off

If I start a screen session with screen -dmS name, how would I access the command history of that screen session with a script?

Using the , the last executed command appears, even in screen.

ANSWER:

I use the default bash shell on my system and so might not work with other shells.

this is what I have in my ~/.screenrc file so that each new screen window gets its own command history:

Default Screen Windows With Own Command History

To open a set of default screen windows, each with their own command history file, you could add the following to the ~/.screenrc file:

screen -t "window 0" 0 bash -ic 'HISTFILE=~/.bash_history.${WINDOW} bash'
screen -t "window 1" 1 bash -ic 'HISTFILE=~/.bash_history.${WINDOW} bash'
screen -t "window 2" bash -ic 'HISTFILE=~/.bash_history.${WINDOW} bash'

Ensure New Windows Get Their Own Command History

The default screen settings mean that you create a new window using Ctrl+a c or Ctrl+a Ctrl+c. However, with just the above in your ~/.screenrc file, these will use the default ~/.bash_history file. To fix this, we will overwrite the key bindings for creating new windows. Add this to your ~/.screenrc file:

bind c screen bash -ic 'HISTFILE=~/.bash_history.${WINDOW} bash'
bind ^C screen bash -ic 'HISTFILE=~/.bash_history.${WINDOW} bash'

Now whenever you create a new screen window, it’s actually launching a bash shell, setting the HISTFILE environmental variable to something that includes the current screen window’s number ($WINDOW).

Command history files will be shared between screen sessions with the same window numbers.

Write Commands to $HISTFILE on Execution

As is normal bash behavior, the history is only written to the $HISTFILE file by upon exiting the shell/screen window. However, if you want commands to be written to the history files after the command is executed, and thus available immediately to other screen sessions with the same window number, you could add something like this to your ~/.bashrc file:

export PROMPT_COMMAND="history -a; history -c; history -r; ${PROMPT_COMMAND}"
Categories: Système Tags: , , ,

Ubuntu Check RAM Memory Chip Speed and Specification From Within a Linux System

22/06/2016 Comments off

I want to add more RAM to my server running Ubuntu Linux. How do I find out my current RAM chip information such as its speed, type and manufacturer name within a Linux system without opening the case?

You need to use the dmidecode command which is a tool for dumping a computer’s DMI (some say SMBIOS) table contents in a human-readable format. This table contains a description of the system’s hardware components (such as RAM), as well as other useful pieces of information such as serial numbers and BIOS revision. Thanks to this table, you can retrieve hardware information without having to probe for the actual hardware. Open a command-line terminal (select Applications > Accessories > Terminal), and then type:

$ sudo dmidecode --type memory

OR

# dmidecode --type memory | less

OR

$ sudo dmidecode --type 17

Sample outputs:

# dmidecode 2.10
SMBIOS version fixup (2.51 -> 2.6).
SMBIOS 2.6 present.
Handle 0x0011, DMI type 16, 15 bytes
Physical Memory Array
	Location: System Board Or Motherboard
	Use: System Memory
	Error Correction Type: None
	Maximum Capacity: 4 GB
	Error Information Handle: Not Provided
	Number Of Devices: 4
Handle 0x0012, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0011
	Error Information Handle: No Error
	Total Width: 72 bits
	Data Width: 64 bits
	Size: 2048 MB
	Form Factor: DIMM
	Set: 1
	Locator: DIMM#1A
	Bank Locator: Bank 1
	Type: DDR2
	Type Detail: Synchronous
	Speed: 667 MHz
	Manufacturer: Not Specified
	Serial Number: Not Specified
	Asset Tag: Not Specified
	Part Number: Not Specified
Handle 0x0013, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0011
	Error Information Handle: No Error
	Total Width: 72 bits
	Data Width: 64 bits
	Size: 2048 MB
	Form Factor: DIMM
	Set: 1
	Locator: DIMM#2A
	Bank Locator: Bank 2
	Type: DDR2
	Type Detail: Synchronous
	Speed: 667 MHz
	Manufacturer: Not Specified
	Serial Number: Not Specified
	Asset Tag: Not Specified
	Part Number: Not Specified
Handle 0x0014, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0011
	Error Information Handle: No Error
	Total Width: 72 bits
	Data Width: 64 bits
	Size: 2048 MB
	Form Factor: DIMM
	Set: 1
	Locator: DIMM#1B
	Bank Locator: Bank 1
	Type: DDR2
	Type Detail: Synchronous
	Speed: 667 MHz
	Manufacturer: Not Specified
	Serial Number: Not Specified
	Asset Tag: Not Specified
	Part Number: Not Specified
Handle 0x0015, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0011
	Error Information Handle: No Error
	Total Width: 72 bits
	Data Width: 64 bits
	Size: 2048 MB
	Form Factor: DIMM
	Set: 1
	Locator: DIMM#2B
	Bank Locator: Bank 2
	Type: DDR2
	Type Detail: Synchronous
	Speed: 667 MHz
	Manufacturer: Not Specified
	Serial Number: Not Specified
	Asset Tag: Not Specified
	Part Number: Not Specified