More (advanced) commands.

awk

Powerful, but somewhat more advanced command!

This command finds patterns in a file and can perform arithmetic/string operations. You can use it to transform data files and produce formatted reports.

It allows the user to use variables, numeric functions, string functions, and logical operators.

Things awk can do:

  • Scan a file line by line
  • Split each input line into fields
  • Compare input line/fields to pattern
  • Perform action(s) on matched lines

Search for the pattern ‘snow’ in the file FILE and print out the first column

awk '/snow/ {print$1}' FILE

Print column 3 and 4 from file mydata.dat

awk '{print $3 "\t" $4}' mydata.dat

Print column 2 and 3 from file mydata.dat, but only those rows that contain the letter ‘r’

awk '/r/ {print $2 "\t" $3}' mydata.dat

chown - change ownership

To change ownership of a file or directory, use the command chown.

chown [OPTIONS] USER[:GROUP] FILE(s)

Examples

  • chown USERNAME FILE the user with USERNAME becomes the new owner of FILE
  • chown USERNAME DIRECTORY the user with USERNAME becomes the new owner of DIRECTORY (but not any subdirectories)
  • chown USERNAME:folk DIRECTORY the user ownership is changed to USER and the group ownership to group “folk” for the directory DIRECTORY
  • chown :folk DIRECTORY the group ownership is changed to the group “folk” for the directory DIRECTORY
  • chown -R USERNAME:folk DIRECTORY the user ownership is changed to USERNAME and the group ownership is changed to group “folk” for the directory DIRECTORY and all subdirectories

Warning

As default, chown does not generate output on success and returns zero.