GREP

• grep (globally search a regular expression and print)
  • very old utility, you will be hard pressed to find a linux distro that doesn’t have grep. There can be variations like egrep and fgrep but you can pretty much guaranteed to have grep.
  • where find and locate will find file names across a hard drive , grep has the ability to search not only across a hard drive but inside of files.
  • • man grep
      • pulls up the manual page for grep
    • grep can do both egrep and fgrep
    • a lot of distros have started doing aliases of egrep and fgrep
    • egrep
      • searches for an extended regular expression
        • eg egrep N* will search for anything starting with N
    • fgrep
      • searches for a regular fixed string
        • eg fgrep NNNNN will search for 5 capital N’s no more no less
        • on most systems fgrep is aliased to grep becoming the default, -E invokes egrep
  • alias will show you a list of alias’s, this way you can tell how grep will behave on your system
  • type egrep will show you an alias
  • which egrep will show you an alias and where the binary is located
    • some systems wont have a binary for egrep opting insted to alias grep -E, this can also be seen with fgrep
  • grep can be pointed at a single file or a whole directory
    • grep -r [search term] will recursively search the current working directory
      • its a good idea to get in the habit of specifying where you want to search and not rely on defaults or assumptions
        • . current working directory
        • .. one level above current working directory
        • ~ users home directory
        • / root level directory