{{tag>bash}}

====== Bash commands ======
===== Remove first character: =====


  for f in *; do mv "$f" "${f:1}"; done

==== Add 8 to filename: ====


  for f in *; do mv "$f" "8$f"; done

==== Sort folders by disk usage, larger first: ====
  du -sh /* | sort -hr

==== Checksum directory recursively ====

  find /var/lib/mysql -type f -print0 | xargs -0 sha256sum > mysql.sha256sum

==== Comment and uncomment lines containing specific strings ====
  sed -e '/multiverse/s/^/#/' -i /etc/apt/sources.list
  sed -e '/multiverse/s/^#//' -i /etc/apt/sources.list

==== Search and replace strings in multiple html files: ====
  for file in $(grep -cr --include "*.html" "somestring" . | awk -F ":" '{print $1}');do sed -i 's/\bsomestring\b/newstring/g' $file;done

\b is word boundary, meaning it won't select strings like string_somestring_smth_smth Put sed -n... and ..newstring/gp' to just see the changes without actually making them.

==== Print from certain line to certain line: ====

  zcat server_20170726-060002.log.gz | awk '/2017-07-25\ 20:54:59.381/,/2017-07-25\ 21:16:00.948/' - > incident.txt

==== Sed add word/string after specific string on same line i.e. add "blablah" after " localhost ": ====
  sed 's/\blocalhost\b/& blablah/' file


==== Print disk usage, summarize in GB ====
   du -s /var/lib/mysql/mydb/{table1,table2,table3}.* | awk '{ sum+=$1} END {printf sum/1024^2; print " GB"}'

==== Remove old unused kernels ====

  sudo dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d'|grep -E "(image|headers|modules)" | grep -v hwe | xargs sudo apt-get -y purge
  
====== Tested on ======
  * 

====== See also ======
  * [[wiki:nginx_logs_parsing_commands]]
====== References ======