Linux Cool Commands

Editing

• vim

  # Remove trailing spaces
  :%s/\s\+$//
  
  

• sed -r ’s/\s+//g' afile

• sort afile|uniq

• sed

  # sed [options] 'row-range+action'  file
  # Actions: i, a, d, c, p, s
  # +g, +i
  
  # In place replacement, original copy with .bk suffix is created
  sed -i.bk  's/Z/1/g' afile
  
  # Remove lines from 3 to end
  sed '3,$d'
  
  # Print line 1 and line 2 only
  sed -n '1,2p' afile
  
  # Print lines match pattern
  sed -n '/A/p' afile
  
  

• awk

  # awk 'pattern{action}' filenames
  last -n 5 | awk '{print $1}'
  
  cat /etc/passwd |awk  -F ':'  'BEGIN {print "name,shell"}  {print $1","$7} END {print "blue,/bin/nosh"}'
  
  awk -F: '/^root/{print $7}' /etc/passwd
  

• cut

  # Print 1st field, each field separated by :
  cut -d: -f 1 /etc/passwd
  

Searching

• find

  find /etc -name passwd
  find . -name "*.txt" -exec echo {} \; -exec grep banana {} \;
  find ./ -type d |xargs ls -l
  
  # -I replace_str; -0 take cares of file names with blank space
  find . -name "*.bak" -print0 | xargs -0 -I {} mv {} ~/old.files
  # {} could be customized as whatever, like file in the example
  find /path/to/dir -iname "*.c" -print0 | xargs -0 -I file mv file ~/old.src
  

• ls

  # List one column
  ls -1
  
  

Logging

• dmesg // kernel message, equals to journalctl -k
• journalctl -a
• /var/log

Resources

• ps -ef|grep java
• top
• vmstat
• sar

Networking

• netstat -anp|grep 80

• lsof -i :80

• tcpdump

Storage

• lsblk
• fdisk -l
• iotop

Kernel

Performance

• time ls
• watch -n 2 free