Commands and Operators

• Many built-in commands available. “man bash” contains complete list. “help <command>” gives usage info for each command, or just “help” to list built-ins.

• Some commands exist as both built-in and separate binaries, i.e.: true, test, time (use “type” command)

• There aren't really “operators” in bash, but the test command, abbreviated as [, gives illusion

  • MHZ=$(grep "cpu MHz" /proc/cpuinfo | cut -d : -f2)
  • MHZINT=`awk -F. '{print $0}'`
  • if [ $MHZINT -lt 500 ]
  • then
    • echo “Your machine is slow. Blame jtate."
  • fi

• $() and `` converts commands' standard out into args.

  • grep :`id -g`: /etc/passwd

Notes: