sed, awk regular expression

sedTake good lines, awkcommand good at taking column

and

• Format :sed <option> <script> <file>

• option

  • -e: Execute multiple commands
    • The command must be separated by a semicolon
    • No space between the end of the command and the semicolon
    • example:sed -e 's/brown/green; s/dog/cat' data.txt
  • -f: Read commands from a file
    • Each command line without the semicolon
    • example:sed -f script.sed data.txt
  • -n: No command output, print output command to complete

• script

  • ** s **: replacement string between the first string between the second slash slash
    • example:echo "a dog" | sed 's/dog/cat/'

• file

  • Not specified defaults to STDIN

• sed does not modify file data, but to send the modified data to STDOUT

awk

• Format :awk <options> <program> <file>

• option

  • -f: Read commands from a file
    • Must {}beginning of the end
    • Each command line without the semicolon
  • -F: Custom field delimiter
    • The default delimiter is whitespace
    • example:awk -F: '{print $1}' /etc/passwd

• program

  • You can customize variables
    • You do not need a custom variable references$
    • The default variable
      • $0On behalf of the entire line of text
      • $11 represents the first data field
      • $nN represents the data fields
  • Keyword
    • BEGIN: Script execution defined later in the pre-processing of data
      • Two single quotes in the command remains the same
      • example:awk 'BEGIN {print "hello world!"} {print $0}'
    • END: After the definition of the script execution in the data processing
  • Semicolon between commands can execute a plurality of commands
    • example:echo "Hello World" | awk '{$2="golang"; print $0}'

• file

  • Not specified defaults to STDIN

  Regular Expressions