Difference between revisions of "Bash"

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  % echo ${test_string:6:5}
 
  % echo ${test_string:6:5}
  
 +
=== Parameter Expansion ===
 +
* ${VAR#pattern} # delete shortest match of pat from the beginning
 +
* ${VAR#pattern} # delete shortest match of pat from the beginning
 
=== Splitting String ===
 
=== Splitting String ===
 
(from [http://stackoverflow.com/a/918931 best answer on stackoverflow])
 
(from [http://stackoverflow.com/a/918931 best answer on stackoverflow])
Line 42: Line 45:
 
==== option 3 ====
 
==== option 3 ====
 
  find . -type f -not \( -name '*zip' -or -name '*iso' \) -delete
 
  find . -type f -not \( -name '*zip' -or -name '*iso' \) -delete
 +
 +
=== Reading dash files ===
 +
(from [https://unix.stackexchange.com/questions/189251/how-to-read-dash-files How to Read Dash Files] on Unix.Stackexchange)
 +
cat -- -file
 +
or
 +
cat < -file
 +
 +
== Programming tips ==
 +
=== raw URL encoding ===
 +
from [https://stackoverflow.com/questions/296536/how-to-urlencode-data-for-curl-command How to urlencode data for curl command?]
 +
<pre>
 +
rawurlencode() {
 +
  local string="${1}"
 +
  local strlen=${#string}
 +
  local encoded=""
 +
  local pos c o
 +
 +
  for (( pos=0 ; pos<strlen ; pos++ )); do
 +
    c=${string:$pos:1}
 +
    case "$c" in
 +
        [-_.~a-zA-Z0-9] ) o="${c}" ;;
 +
        * )              printf -v o '%%%02x' "'$c"
 +
    esac
 +
    encoded+="${o}"
 +
  done
 +
  echo "${encoded}"    # You can either set a return variable (FASTER)
 +
  REPLY="${encoded}"  #+or echo the result (EASIER)... or both... :p
 +
}
 +
</pre>
  
 
== ShellShock (CVE-2014-7186 and CVE-2014-7187) ==
 
== ShellShock (CVE-2014-7186 and CVE-2014-7187) ==

Latest revision as of 15:32, 28 October 2020

Bourne-Again SHell (bash) is a Unix/Linux shell.

Contents

Tips

Substrings

(from Bash Guide for Beginners) 

% export test_string="Hello World"
% echo ${test_string:6:5}

Parameter Expansion

  • ${VAR#pattern} # delete shortest match of pat from the beginning
  • ${VAR#pattern} # delete shortest match of pat from the beginning

Splitting String

(from best answer on stackoverflow) 

read -ra ADDR <<< "$IN"

can be modified, thusly: 

IFS=';' read -ra ADDR <<< "$IN"

Testing Exit Value 

if [ $? -eq 0 ] ; then good ; else bad ; fi

Redirection

To redirect stderr and stdout to a file: 

prog &> file

see All about redirection

Remove all but some files

(from Linux: Bash Delete All Files In Directory Except Few)

option 1 

shopt -s extglob
rm !(*.zip|*.iso)
shopt -u extglob

option 2

(see GLOBIGNORE in bash(1)) 

GLOBIGNORE=*.zip:*.iso
rm -v *
unset GLOBIGNORE

option 3 

find . -type f -not \( -name '*zip' -or -name '*iso' \) -delete

Reading dash files

(from How to Read Dash Files on Unix.Stackexchange) 

cat -- -file

or 

cat < -file

Programming tips

raw URL encoding

from How to urlencode data for curl command? 

rawurlencode() {
  local string="${1}"
  local strlen=${#string}
  local encoded=""
  local pos c o

  for (( pos=0 ; pos<strlen ; pos++ )); do
     c=${string:$pos:1}
     case "$c" in
        [-_.~a-zA-Z0-9] ) o="${c}" ;;
        * )               printf -v o '%%%02x' "'$c"
     esac
     encoded+="${o}"
  done
  echo "${encoded}"    # You can either set a return variable (FASTER) 
  REPLY="${encoded}"   #+or echo the result (EASIER)... or both... :p
}

ShellShock (CVE-2014-7186 and CVE-2014-7187)

External links

Retrieved from "https://gnosia.anu.edu.au/mw/index.php?title=Bash&oldid=3061"