Linux Journal September 2026

qotd: “f yourself!” – gigi murin

• grep
  • echo -e “abc\nedf” | grep d -> edf
    • -e for escaping backlash
    • grep return all matching character along with content of their lines
    • | (pipe symbol) will take the output of the previous command and use it as the input for the next command
  • echo -e “abc\ndef” | grep -v d -> abc
    • -v reverse the output meaning rather than returning all the instances where the certain character exist, it’ll give only lines where the a character is not there
  • rather than cat, use grep -> grep “error” /some/path
    • chain with -v -> grep “error” /some/path | grep -v dotnet
    • add wc to count word characters
  • -n flag to add a number line for each result
    • grep “error” /var/log/syslog | grep -n apparmor
  • by default most linux command are case sensitive, add -i to make case insensitive
    • grep “error” /var/log/syslog | grep -ni apparmor
  • using grep with special characters:
    • example: cat /var/log/syslog | grep Can’t update
      • single quote in a string interpreted the character as an opening quote and expected there a closing quote. and even without single quote it will failed because of space
      • simply using double quote cat /var/log/syslog | grep “Can’t”