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=Links=
*[http://www.gnu.org/software/bash/bash.html Homepage]  
*[http://www.gnu.org/software/bash/bash.html Homepage]  


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*[https://www.cyberciti.biz/faq/bash-shell-change-the-color-of-my-shell-prompt-under-linux-or-unix/ Change colour of bash prompt]  
*[https://www.cyberciti.biz/faq/bash-shell-change-the-color-of-my-shell-prompt-under-linux-or-unix/ Change colour of bash prompt]  


 


 


= Tips and tricks =
= Tips and tricks =
==Globbing==
===Globbing except strings===
GLOBIGNORE="*.error.log"


== String manipulation ==
== String manipulation ==
Line 25: Line 26:
  VERSION='2.3.3'
  VERSION='2.3.3'
  echo "${VERSION//.}"
  echo "${VERSION//.}"
=== Replace all characters in a string===
Replace all x,y,z with _:
"${var//+([xyz])/_}"
requires extended pattern matching
shopt -s extglob


=== check if var contains substring ===
=== check if var contains substring ===
Line 80: Line 87:
== bash history timestamp ==
== bash history timestamp ==


  HISTTIMEFORMAT="%d/%m/%y %T "
  HISTTIMEFORMAT="%y/%m/%d %T "


== screen and bash history ==
== screen and bash history ==
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  function foo() {
  function foo() {
     echo $1 $2
     echo "one: $1 two: $2"
   }
   }
foo "first param" 2


=== convert units ===
=== convert units ===
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  mountpoint /mnt/foo
  mountpoint /mnt/foo
== Get local IP address ==
ip route get 1 | awk '{print $NF;exit}'


= FAQ =
= FAQ =
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try qouting your vars
try qouting your vars
   [[Category:Scripting]] [[Category:Programming]]
   [[Category:Scripting]] [[Category:Programming]] [[Category:Shell]]
 
 
== failing I-search backward ==
When stuck at that, try
^g
==bash: printf: 60.29: invalid number==
Check $LC_NUMERIC
 
 
==Variable scope in while loop==
N=0
shopt -s lastpipe
foo | while read i
do
  N=$((N+1))
etc
done
echo $N

Latest revision as of 10:44, 3 September 2024

Links


Tips and tricks

Globbing

Globbing except strings

GLOBIGNORE="*.error.log"

String manipulation

Remove character from string

VERSION='2.3.3'
echo "${VERSION//.}"

Replace all characters in a string

Replace all x,y,z with _:

"${var//+([xyz])/_}"

requires extended pattern matching

shopt -s extglob

check if var contains substring

$foo =~ .*sub.*

get first character of a string

FIRST=${STRING:0:1}


Date manipulation

Age of a file

stat -C %Y $FILE

read without while loop

The problem is scope, try

echo foo bar | { read a b;echo $b; }

check if variable is integer

if [[$foo =~ ^[0-9]+$]]

 

 

move cursor

^b move back 1 char
^f move forward 1 char
alt-b move back 1 word
alf-f move forward 1 word

loops

loop through range of numbers

for i in {0..10};do echo $i;done

 

exit while loop

break

 

skip one in loop

continue

bash history timestamp

HISTTIMEFORMAT="%y/%m/%d %T "

screen and bash history

To make sure all screens write to same history (at least on CentOS and RHEL):

echo "history -a;history -r" > /etc/sysconfig/bash-prompt-screen
chmod +x /etc/sysconfig/bash-prompt-screen

In general:

export PROMPT_COMMAND='history -n'

or

export PROMPT_COMMAND="history -a; history -c; history -r; ${PROMPT_COMMAND}"

add extensions to filenames

find . -type f |while read i;do if ! $i =~ .*.txt;then mv -v $i $i.txt;fi;done

 

functions

function foo() {
   echo "one: $1 two: $2"
 }
foo "first param" 2

convert units

function convertunits() {

       C="$1"
       U="$2"
       debug "converting $C $U"
       case $U in
               "KiB") O=$((C*1000)) ;;
               "MiB") O=$((C*1000*1000)) ;;
               "GiB") O=$((C*1000*1000*1000)) ;;
               "TiB") O=$((C*1000*1000*1000*1000)) ;;
               *) O="convert error in $U" ;;
       esac
       if [ -z "$O" ];then O="convert_error for unit $U";fi
       echo "$O"

}

Check if disk is mounted

mountpoint /mnt/foo

Get local IP address

ip route get 1 | awk '{print $NF;exit}'

FAQ

unary operator expected

try qouting your vars


failing I-search backward

When stuck at that, try

^g

bash: printf: 60.29: invalid number

Check $LC_NUMERIC


Variable scope in while loop

N=0
shopt -s lastpipe
foo | while read i
do
 N=$((N+1))
etc
done
echo $N